Construction of Universal motor – Construction of a universal motor is very similar to the construction of a DC machine, It consists of a stator on which field poles are mounted. Field coils are wound on the field poles. However, the whole magnetic path (stator field circuit and also armature) is laminated.

Lamination is necessary to minimize the eddy currents which induce while operating on AC. The rotary armature is of wound type having straight or skewed slots and commutator with brushes resting on it. The commutation on AC is poorer than that for DC. because of the current induced in the armature coils.

For that reason brushes used are having high resistance.

What type of motor is a universal motor?

This is a type of AC commutator motor. Although mainly used on single-phase AC, it rotates on both AC and DC power. It is also called a ‘universal motor’ or ‘commutator motor’.

Is AC series motor and universal motor same?

Ac Series Motor vs Universal Motor 2019-04-30 09:03:18 2434 All the motors in mechanical devices including household appliances can generally fall into three categories depending on the current they use. We have AC motors, DC motors, and universal motors.

Each motor will have its unique features that set it apart from the rest, and it will also have different capabilities. To learn more about the different motors, it is better to compare two types of motors rather than all three together. This article will therefore focus on ac series motor vs universal motor.

In essence, an AC series motor is a modified DC series motor. If you tried to run a DC series motor on AC power supply, you would experience numerous problems. For one, it would be prone to overheating, and it would also not generate enough power. For this reason, the DC series motor is modified so that it can use AC supply.

• In the AC series motor, the armature and field are still wound and interconnected just as in the DC series motor.
• Its magnetic circuit is, however, laminated, a low-reluctance magnetic circuit is used, and high-resistance leads are used to connect the coils to the commutator.
• With these changes, the AC series motor can now use single phase AC supply.

The universal motor, on the other hand, can run on both single-phase AC and DC supply hence the name universal. It is also highly modified so that it can run on both types of current. Given the same voltage, a universal motor will have higher speeds on DC supply than on AC supply because of the voltage drop that exists on AC supply.

The interesting thing is that whether the universal motor is connected to AC or DC supply, it will still work as a DC series motor due to its design and modifications. It has low speed at full load and high speed at low load. When it comes to application and advantages, there are some differences in the AC series motor vs universal motor.

The universal motor is the most preferred motor for home appliances such as blenders, food mixers, vacuum cleaners sewing machines and electric shavers. Commercially it is common in drills and other heavy machinery. The ac series motor has the benefit of being more efficient, reliable and durable than the universal motor.

What are the two types of universal motor?

Universal Motor – The universal motor is a unique type of motor which runs on either DC or single-phase AC supply. These motors are usually series wound and produce high starting torque. Hence, universal motors are built into the devices meant to drive.

What is universal motor example?

You are here: Home / New Articles / Basics of universal electric motors For a rotary electric motor to work, there must be two magnetic fields, one associated with the stator and the other with the rotor. At least one of these fields must be moving so the rotor’s magnetic field constantly pursues the stator’s magnetic field, thus creating rotary mechanical motion and energy output.

One of the magnetic fields can be stationary, created by permanent magnets or dc voltage (in the case of a brushed dc motor) applied directly to the stator windings. Or it can be created through brushes and slip rings to the rotor. The other alternative is that both magnetic fields rotate, as in an induction motor.

For this to work, the magnetic fields must rotate at different speeds. If these fields were exactly in synch, (hypothetically) there would be no interaction of the magnetic fields and no rotary motion. In an induction motor, because of frictional drag or loading on the shaft, the rotor turns more slowly than the stator’s rotating field. The schematic for a universal motor is quite simple. The stator windings connect in series with windings in the rotor by means of carbon brushes. In the universal motor, the situation is strikingly different. A universal motor contains stator windings and rotor windings.

Current in the rotor windings is not strictly the result of inductive coupling as in the induction motor. The defining characteristic of the universal motor with respect to its construction is that the stator and rotor windings are wired in series. This serves to create a voltage difference between them so the rotor can pursue the stator’s rotating magnetic field.

Current is channeled into the rotor through brushes. Universal motors are theoretically able to operate on ac or dc. The unit as described above, however, would thrive on dc but not operate efficiently on ac. To run well off ac mains, the motor needs modifications. Series-wound (universal) electric motors respond to a bigger load by slowing down — the current rises, then torque rises in proportion to the square of the current because the same current flows in both the stator and rotor windings. The speed almost entirely depends on the torque required to drive the load.

• The ac-operated universal motor is common in the home and workplace.
• It is appropriate for small appliances and tools that require comparatively high power.
• Examples include portable hand tools, blenders, vacuum cleaners and sewing machines.
• The universal motor may be recognized by its distinctive whirring sound when running.

If poor performance such as failure to start is noted, the answer is to replace the brushes, which are accessible without motor disassembly. If this is deferred, there will be far more expensive commutator damage.

What is universal motor Mcq?

Universal Motors MCQ – Objective Question Answer for Universal Motors Quiz – Download Now! Which of the following motor is best suited for an application where high speed and high torque is required?

1. Universal Motor.
2. Shaded pole motor
3. Capacitor start motor
4. Capacitor start capacitor run motor

Option 1 : Universal Motor. The correct answer is option 1): Universal Motor. Concept:

• A universal motor is a special type of motor which can run on both AC and DC power supplies.
• Universal motors are series-wound Motors. Armature and field coils are in series.
• It has a high starting torque.
• The universal motors are meant to operate at speeds as high as 3500 RPM.
• This is due to the reactance voltage drop that is present only in AC and not in DC.
• It is suitable for High torque applications
• Hence the supply voltage of the universal motor is changed from AC to DC it will act as a DC series motor.

​ Additional Information AC Drive:

• AC drives are used to step-less speed control of motors mostly used in process industries due to their ruggedness and maintenance-free long life.
• Speed control of AC drive mainly achieved by voltage-frequency speed control by means of a power semiconductor-based device.
• Squirrel cage induction motor is widely used in AC drive due to its simple and rugged construction.
• AC drive is available at various voltage levels and there is no limit on the operating voltage.
• For the same power rating, the weight of the AC motor drive is less than that of the DC motor drive.

DC Drive:

• The main reason for using a DC drive is that it has a wide range of speed control. It has high starting torque (DC Series motor) and hence can be used in traction, steel rolling mills, etc.
• It gives a fast response with the input parameter and can provide smooth speed control. It has the ability to quickly starting and stop.
• The cost of a DC motor drive is more than that of an AC motor drive because of additional equipment required for DC supply such as a converter, battery, etc.

India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students The starting torque of universal motor is_.

1. 200 Percent of running torque
2. 50 Percent of running torque
3. 450 Percent of running torque
4. 100 Percent of running torque

Option 3 : 450 Percent of running torque The correct answer is (option 3) i.e.450 Percent of running torque Concept: Universal Motor:

• Universal motor is a commutated series-wound motor
• It can operate on either AC or DC power and uses an electromagnet as its stator to create its magnetic field
• These motors are generally series wound (armature and field winding are in series), and hence produce high starting torque. That is 450% of running torque.
• So, universal motors are generally built into the device they are meant to drive as they have variable speed characteristics.
• Most of the universal motors are designed to operate at higher speeds, exceeding 3500 rpm

Important Points

• Hysteresis motor: Low power factor, low starting torque
• Capacitor start motor: High starting torque, low power factor
• Capacitor run motor: Low starting torque, high power factor
• Universal motor: High speed, high starting torque, operate on either AC or DC power

India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students At full load, the power factor of a universal series motor is about: Universal motor:

• A universal motor is a special type of motor which is designed to run on either DC or single-phase AC supply.
• These motors are generally series wound (armature and field winding are in series), and hence produce high starting torque.
• Most of universal motors are designed to operate at higher speeds, exceeding 3500 RPM.
• They run at a lower speed on AC supply than they run on DC supply of the same voltage, due to the reactance voltage drop which is present in AC and not in DC.
• The speed/load characteristics of a universal motor are similar to that of a DC series motor.
• The speed of a universal motor is low at full load and very high at no load.
• At full load, the power factor of a universal series motor is about 0.9

The speed/load characteristics (for both AC as well as DC supply) are shown in the below figure: India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students The drive motor used in a mixer-grinder is:

1. a universal motor
2. a synchronous motor
3. an induction motor
4. a DC motor

Option 1 : a universal motor

• The universal motor is generally used as the drive motor in mixer grinders.
• The universal motor works on AC and DC supplies and is used in home appliances like fans, mixer grinders, refrigerators, etc.
• This motor uses an electromagnet as its stator to create the magnetic field.
• It has been characterized to have higher power output with the smaller size and starting torque to be high at a lower speed and carry high loads.

India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students The direction of rotation of universal motor can be reversed by reversing the flow of current through

1. armature winding only
2. armature winding or field winding
3. field winding only
4. None of the above

Option 2 : armature winding or field winding Universal motor:

• The motors which can be used with a single-phase AC source, as well as a DC source of supply and voltages, are called Universal Motor.
• It is basically a single-phase DC series motor.
• On reversing the polarity of the line terminals of a DC Series Motor, the motor will continue to run in the same direction.
• A universal motor is a commutation type motor.

Connected to a DC power source: It works just like a DC motor. It has commutator rings which allow unidirectional current is made to flow through the coil and make the torque action unidirectional and the rotor continues to rotate. Connected to an AC power source:

• When using a universal motor with an AC supply, the torque produced by the motor will be positive during the positive half cycle (Since both armature and field current are in the same direction).
• During a negative half cycle, the direction of both armature and field current gets reversed resulting in torque produced in the same direction. (Torque remains positive)

Speed of universal motor: Speed is higher in DC excitation compared to AC excitation as additional losses occur in the case of ac excitation. The direction of rotation of a universal motor can be changed by either:

1. Reversing the field connection with respect to those of armature
2. By using two field windings wound on the core in opposite directions so that the one connected in series with the armature gives clockwise rotation, while the other in series with the armature gives a counterclockwise rotation

India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students Which of the following motors is operated either on direct or single-phase AC supply and produces approximately the same speed and output?

1. Universal motor
2. Capacitor start and capacitor run induction motor
3. Capacitor start induction run motor
4. 1-phase series motor

Option 1 : Universal motor Universal Motor:

• The motors which can be used with a single-phase AC source, as well as a DC source of supply and voltages, are called Universal Motor.
• It is basically a single-phase DC series motor.
• On reversing the polarity of the line terminals of a DC Series Motor, the motor will continue to run in the same direction.
• A universal motor is a commutation type motor.
• The universal motor produces approximately the same speed and output when operated either on a direct or single-phase AC source.

• Important Points:
• The universal motor can work on both AC and DC.
• However, a series motor that is mainly designed for DC operation, it works on single-phase AC supply suffers from the following drawbacks.

• The efficiency becomes low because of hysteresis and eddy current losses.
• The power factor is low due to the large reactance of the field and the armature windings.
• The sparking at the brushes is in excess.

To overcome the above drawbacks, certain modifications are made in a DC series motor so that it can work even on the AC current. Applications of Universal motor:

• Portable drill machine
• Used in hairdryers, grinders and table fans
• It is also used in blowers, polishers and kitchen appliances
• It is used for the purposes where speed control and high values of the speed are necessary

India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students For a given applied voltage and current, the speed of a universal motor will be

1. higher in dc excitation than in ac excitation
2. higher in ac excitation than in dc excitation
3. same in both dc and ac excitations
4. dangerously high in dc excitation

Option 1 : higher in dc excitation than in ac excitation Universal motor:

• The motors which can be used with a single-phase AC source, as well as a DC source of supply and voltages, are called Universal Motor.
• It is basically a single-phase DC series motor.
• On reversing the polarity of the line terminals of a DC Series Motor, the motor will continue to run in the same direction.
• A universal motor is a commutation type motor.

Connected to a DC power source: It works just like a DC motor. It has commutator rings which allow unidirectional current is made to flow through the coil and make the torque action unidirectional and the rotor continues to rotate. Connected to an AC power source:

• When using a universal motor with an AC supply, the torque produced by the motor will be positive during the positive half cycle (Since both armature and field current are in the same direction).
• During a negative half cycle, the direction of both armature and field current gets reversed resulting in torque produced in the same direction. (Torque remains positive)

Speed of universal motor: Speed is higher in DC excitation compared to AC excitation as additional losses occur in the case of ac excitation. India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students Which of the following single-phase motors will work satisfactorily with direct current and alternating current?

1. Universal motor
2. Repulsion motor
3. Single-phase induction motor
4. Capacitor start capacitor run motor

Option 1 : Universal motor Universal Motor:

• The motors which can be used with a single-phase AC source, as well as a DC source of supply and voltages, are called Universal Motor.
• It is basically a single-phase DC series motor.
• On reversing the polarity of the line terminals of a DC Series Motor, the motor will continue to run in the same direction.
• A universal motor is a commutation-type motor.
• The universal motor produces approximately the same speed and output when operated either on a direct or single-phase AC source.

1. Important Points
2. The universal motor can work on both AC and DC.
3. However, a series motor that is mainly designed for DC operation, it works on a single-phase AC supply suffers from the following drawbacks.

• The efficiency becomes low because of hysteresis and eddy current losses.
• The power factor is low due to the large reactance of the field and the armature windings.
• The sparking at the brushes is in excess.

To overcome the above drawbacks, certain modifications are made in a DC series motor so that it can work even on the AC current. Applications of Universal motor:

• Portable drill machine
• Used in hairdryers, grinders and table fans
• It is also used in blowers, polishers and kitchen appliances
• It is used for the purposes where speed control and high values of the speed are necessary

India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students At full load, the power factor of a universal series motor is about: Universal motor:

• A universal motor is a special type of motor which is designed to run on either DC or single-phase AC supply.
• These motors are generally series wound (armature and field winding are in series), and hence produce high starting torque.
• Most of universal motors are designed to operate at higher speeds, exceeding 3500 RPM.
• They run at a lower speed on AC supply than they run on DC supply of the same voltage, due to the reactance voltage drop which is present in AC and not in DC.
• The speed/load characteristics of a universal motor are similar to that of a DC series motor.
• The speed of a universal motor is low at full load and very high at no load.
• At full load, the power factor of a universal series motor is about 0.9

The speed/load characteristics (for both AC as well as DC supply) are shown in the below figure: India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students The direction of rotation of universal motor can be reversed by reversing the flow of current through

1. armature winding only
2. armature winding or field winding
3. field winding only
4. None of the above

Option 2 : armature winding or field winding Universal motor:

• The motors which can be used with a single-phase AC source, as well as a DC source of supply and voltages, are called Universal Motor.
• It is basically a single-phase DC series motor.
• On reversing the polarity of the line terminals of a DC Series Motor, the motor will continue to run in the same direction.
• A universal motor is a commutation type motor.

Connected to a DC power source: It works just like a DC motor. It has commutator rings which allow unidirectional current is made to flow through the coil and make the torque action unidirectional and the rotor continues to rotate. Connected to an AC power source:

• When using a universal motor with an AC supply, the torque produced by the motor will be positive during the positive half cycle (Since both armature and field current are in the same direction).
• During a negative half cycle, the direction of both armature and field current gets reversed resulting in torque produced in the same direction. (Torque remains positive)

• Speed of universal motor:
• Speed is higher in DC excitation compared to AC excitation as additional losses occur in the case of ac excitation.
• The direction of rotation of a universal motor can be changed by either:

1. Reversing the field connection with respect to those of armature
2. By using two field windings wound on the core in opposite directions so that the one connected in series with the armature gives clockwise rotation, while the other in series with the armature gives a counterclockwise rotation

India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students The drive motor used in a mixer-grinder is:

1. a universal motor
2. a synchronous motor
3. an induction motor
4. a DC motor

Option 1 : a universal motor

• The universal motor is generally used as the drive motor in mixer grinders.
• The universal motor works on AC and DC supplies and is used in home appliances like fans, mixer grinders, refrigerators, etc.
• This motor uses an electromagnet as its stator to create the magnetic field.
• It has been characterized to have higher power output with the smaller size and starting torque to be high at a lower speed and carry high loads.

India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students A single-phase universal motor is operated with AC source. The torque of the motor during the negative half cycle of the input current:

1. Follows the same pattern of the torque caused by the positive half-cycle of the input current
2. is half of the torque caused by the positive half cycle of the input current
3. is negative
4. is zero

Option 1 : Follows the same pattern of the torque caused by the positive half-cycle of the input current Concept: Universal motor:

• A universal motor is a special type of motor which is designed to run on either DC or single phase AC supply. These motors are generally series wound (armature and field winding are in series), and hence produce high starting torque.
• They run at lower speed on AC supply than they run on DC supply of same voltage, due to the reactance voltage drop which is present in AC and not in DC.

Construction:

• Construction of a universal motor is very similar to the construction of a DC machine,
• It consists of a stator on which field poles are mounted. Field coils are wound on the field poles. However, the whole magnetic path (stator field circuit and also armature) is laminated. Lamination is necessary to minimize the eddy currents which induce while operating on AC.
• The rotary armature is of wound type having straight or skewed slots and commutator with brushes resting on it. The commutation on AC is poorer than that for DC. Because of the current induced in the armature coils. For that reason brushes used are having high resistance.

Working:

• When fed with AC supply, it still produces unidirectional torque, Because, armature winding and field winding are connected in series, they are in same phase.
• Hence, as polarity of AC changes periodically, the direction of current in armature and field winding reverses at the same time.
• Thus, direction of magnetic field and the direction of armature current reverses in such a way that the direction of force experienced by armature conductors remains same.
• Thus, regardless of AC or DC supply, universal motor works on the same principle that DC series motor works.

India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students A universal motor is one which

1. is available universally
2. can be marketed intentionally
3. can be operated either on dc or ac supply
4. runs dangerously high speed on no load

Option 3 : can be operated either on dc or ac supply

• The motors which can be used with a single-phase AC source, as well as a DC source of supply and voltages, are called Universal Motor.
• It is basically a single-phase DC series motor.
• On reversing the polarity of the line terminals of a DC Series Motor, the motor will continue to run in the same direction.
• A universal motor is a commutation type motor.

1. Important Points:
2. The universal motor can work on both AC and DC.
3. However, a series motor that is mainly designed for DC operation, it works on single-phase AC supply suffers from the following drawbacks.

• The efficiency becomes low because of hysteresis and eddy current losses.
• The power factor is low due to the large reactance of the field and the armature windings.
• The sparking at the brushes is in excess.

To overcome the above drawbacks, certain modifications are made in a DC series motor so that it can work even on the AC current. Applications of Universal motor:

• Portable drill machine
• Used in hairdryers, grinders and table fans
• It is also used in blowers, polishers and kitchen appliances
• It is used for the purposes where speed control and high values of the speed are necessary

India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students A universal motor has high starting torque and a variable speed characteristics because it is _.

1. Shunt wound
2. Long shunt wound
3. Compound wound
4. Series wound

Universal motor:

• Universal motor is a commutated series-wound motor
• It can operate on either AC or DC power and uses an electromagnet as its stator to create its magnetic field
• These motors are generally series wound (armature and field winding are in series), and hence produce high starting torque
• So, universal motors are generally built into the device they are meant to drive as they have variable speed characteristics.
• Most of the universal motors are designed to operate at higher speeds, exceeding 3500 rpm
• Thus, under normal operating conditions universal motor can run at 5000 rpm

India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students An outstanding feature of a universal motor is it’s

1. Best performance at 50 Hz supply
2. Slow speed at all loads
3. Excellent performance on DC supply
4. Highest kW/kg ratio

Option 4 : Highest kW/kg ratio The correct answer is ‘option 4’ Solution:

• A universal motor is a special type of motor that runs on both AC and DC power supplies.
• Universal motors are series-wound (the armature and field windings are in series).
• The series connection allows them to generate high torque, hence the universal motors are generally built into the device they are meant to drive.
• Most of the universal motors are meant to operate at speeds as high as 3500 RPM.
• These motors run at a higher speed on DC supply than they run on AC supply of the same voltage.
• This is due to the reactance voltage drop that is present only in AC and not in DC.

Properties of Universal Motors Following are the distinctive properties of the universal motor:

• They run at high speed.
• They have high starting torque.
• Compact size and are lightweight.
• They are noisy because of the commutator and brushes.

• Additional Information
• Applications of Universal Motor:
• Universal motors are used in applications where high speed and good speed control is necessary.
• Following are the various applications of universal motor:

• Universal Motors are used in table fans, hairdryers and grinders.
• They are used in portable drill machines.
• They are used in polishers, blowers and kitchen appliances.

India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students : Universal Motors MCQ – Objective Question Answer for Universal Motors Quiz – Download Now!

Is DC series motor a universal motor?

Free ST 1: Basic Electrical Engineering 20 Questions 20 Marks 20 Mins

The motors which can be used with a single-phase AC source, as well as a DC source of supply and voltages, are called Universal Motor. It is basically a single-phase DC series motor. On reversing the polarity of the line terminals of a DC Series Motor, the motor will continue to run in the same direction. A universal motor is a commutation type motor.

Important Points: The universal motor can work on both AC and DC. However, a series motor that is mainly designed for DC operation, it works on single-phase AC supply suffers from the following drawbacks.

The efficiency becomes low because of hysteresis and eddy current losses. The power factor is low due to the large reactance of the field and the armature windings. The sparking at the brushes is in excess.

To overcome the above drawbacks, certain modifications are made in a DC series motor so that it can work even on the AC current. Applications of Universal motor:

Portable drill machine Used in hairdryers, grinders and table fans It is also used in blowers, polishers and kitchen appliances It is used for the purposes where speed control and high values of the speed are necessary

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Which DC motor is universal motor?

Which Is Called Universal Motor? – This is an AC commutator motor of the kind. It rotates on both AC and DC power, although being mostly utilized on single-phase AC. It’s also known as a “commutator motor” or “universal motor.” The Universal motor’s great power density is one of its key advantages.

How are DC series motors similar to AC motors?

The characteristics of the AC series motor are identical to that of DC types. The torque is related to the square of the armature current (TI 2 ) and the velocity is inversely related to the armature current.

Why a universal motor can work on AC and DC?

You are here: Home / FAQs + basics / How can a universal motor operate on either DC or AC supply? A universal motor is a series-wound motor — meaning that the field and armature windings are connected in series — and is mechanically commutated with brushes and a commutator. For proper operation with AC supply, a universal motor incorporates a compensation winding, in series with the armature and field winding. Image credit: circuitglobe.com When the motor runs on AC voltage, the alternating flux causes a reactance voltage, which limits the current to a much lower level than would be produced with DC voltage.

To limit the effects of this armature reaction, the universal motor uses a compensation winding, which is installed in the slots of the stator, 90 degrees electrical from the main field winding and connected in series with the armature and field winding. (This arrangement is referred to as “conductively compensated.”) The current flowing in each coil of the compensating winding is in a direction opposite to the current in the corresponding armature loop near it.

The winding of equal coils in opposite directions produces a cancelling effect that reduces inductance, and therefore, reactance. AC supply also induces more significant eddy currents than are produced when the motor operates on DC supply. To curtail eddy current losses, universal motors use laminated cores (rather than solid iron), which increases their resistance and reduces eddy currents. Armature reaction changes the location of the magnetic neutral plane, which is the axis along which the brushes should be mounted. Image credit: Precision Microdrives Limited It is because the armature and field windings are connected in series that a universal motor can operate with either DC or AC supply. To reduce inductance in the armature, the current flowing in each coil of the compensating winding is in a direction opposite to the current in the corresponding armature loop near it. Image credit: Festo Didactic One of the primary benefits of a universal motor is its ability to achieve (theoretically) unlimited speed, with speeds up to 20,000 rpm in real-world applications.

The speed-torque curve is essentially a straight line between stall torque (zero speed) and no-load speed (zero torque), meaning that as the load (torque) increases, the speed decreases. In fact, like a series-wound DC motor, running a universal motor with no load (zero torque) could lead to a runaway condition, where the speed increases until the motor begins to break apart.

The converse of this phenomenon is that universal motors produce very good starting torque (high torque at low speeds). A universal motor can produce extremely high speed at zero torque, but speed drops rapidly as torque increases. Image credit: Groschopp, Inc. This ability to run at very high speeds means that universal motors are good for applications that involve rapidly spinning components, such as fans, blow dryers, and vacuum cleaners.

And their ability to produce high torque at low speeds makes them suitable for applications such as blenders and portable drills. Because they’re mechanically commutated, universal motors generally aren’t suitable for continuous-duty applications, due to brush maintenance and wear. The brushes also make them relatively noisy, so their primary areas of application are small consumer appliances.

Feature image credit: Groschopp, Inc.

Why is a universal motor used?

Modern low-cost universal motor, from a vacuum cleaner, Field windings are of copper wire, toward the back on both sides. The rotor’s laminated metallic core is gray, with darker slots for winding the coils having high efficiency. The similarly shaped metallic commutator (partly hidden toward the front) has become dark from use.

1. The large brown molded-plastic piece in the foreground supports the brush guides and brushes (both sides), as well as the front motor bearing.
2. The universal motor is a type of electric motor that can operate on either AC or DC power and uses an electromagnet as its stator to create its magnetic field.

It is a commutated series-wound motor where the stator ‘s field coils are connected in series with the rotor windings through a commutator, It is often referred to as an AC series motor. The universal motor is very similar to a DC series motor in construction, but is modified slightly to allow the motor to operate properly on AC power.

1. This type of electric motor can operate well on AC because the current in both the field coils and the armature (and the resultant magnetic fields) will alternate (reverse polarity) synchronously with the supply.
2. Hence the resulting mechanical force will occur in a consistent direction of rotation, independent of the direction of applied voltage, but determined by the commutator and polarity of the field coils.

Universal motors have high starting torque, can run at high speed, and are lightweight and compact. They are commonly used in portable power tools and equipment, as well as many household appliances. They’re also relatively easy to control, electromechanically using tapped coils, or electronically.

Which is the application of universal motor Mcq?

Electrical Machines Questions and Answers – Machine Applications

This set of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “Machine applications”.1. Synchronous-induction coupled motors are required for _ a) high starting torque applications b) high pull out torque applications c) high running torques applications d) none of the mentioned View Answer

Answer: a Explanation: Induction motor provides high starting torque with proper values of slip ring terminal resistance. Coupled along with the synchronous motor it acts as an independent set and be employed in high torque application.2. Which of the following can be used for braking purposes in electric trains? a) Induction generator b) Induction motor c) Dc series motor d) Dc differentially compounded generator View Answer Answer: a Explanation: Induction generator runs at a speed greater than the synchronous speed.

• To apply in braking purposes the induction generator can be run in the opposite direction to that of the operating machine direction and stopped.3.
• A synchronous motor absorbing 60 kW is connected in parallel with an continuous load of 240 kW operating at 0.8 power factor lag.What is the kVAR supplied by the synchronous motor to obtain a total power factor of 0.9 lagging? a) 35, leading b) 35, lagging c) 145, leading d) None of the mentioned View Answer Answer: a Explanation: Total power = 240 + 60 = 300 kW cos(phi) = 0.90.

Total reactive power = P*tan(phi) = 300*tan(25.8) = 180 kVAR Load kVAR = 240*tan(36.87) = 180 kVAR kVAR supplied by the motor = 145-180 = -35 or k3 kVAR leading.4. The most widely used application of ac series motor is _ a) electric traction upto 1600 kW b) paper mills c) welding d) none of the mentioned View Answer Answer: d Explanation: Ac series motor is dc series motor connected to ac supply having an unidirectional torque, which is not very high in magnitude.It is widely applicable for small torque requirements like portable drilling machines, mixers etc.5.

• Universal motor is used in vacuum cleaners, table fans and portable drilling machine.
• A) True b) False View Answer Answer: a Explanation: The universal motor is dc series motor with ac supply with smaller torque.
• So it can be used for lower torque applications.
• Participate in of the Month Now! 6.
• Generator is used in arc welding purposes.

a) Differential compound dc b) Dc series c) Cumulative compounded dc d) Shunt View Answer Answer: a Explanation: The external characteristics of the differentially compound generator have minimum voltage for the high current voltages. This is best harnessed feature for a high current requirement by the welding application.7.

The dc series generator is employed as _ a) a booster to maintain constant voltage at the end of the feeder b) for supplying traction load c) for battery bank charging d) none of the mentioned View Answer Answer: a Explanation: Referring to the external characteristics of dc series generator shows that the terminal end voltage increases as the loading increases from no load to full load.

In feeders due to variable requirements the voltage drops while transferring when loading is raised.8. If it asked by the customer to provide tappings on the transformer, the most efficient and economical way to provide it at _ a) middle of hv winding b) phase end of hv winding c) neutral end of hv winding d) middle of lv winding View Answer Answer: a Explanation: Tappings are provided to tap different levels of voltages at the high voltage end of the transformer.

Providing it as low voltage side has no use and it is not economical.9. In a single phase induction regulator, the voltage boost is maximum when armature mmf and rotor mmf make an angle of _ a) zero degrees b) 45 degrees c) 90 degrees d) 180 degrees View Answer Answer: a Explanation: To obtain a maximum of the voltage in induction regulator, the stator mmf and rotor mmf should be stationary and aligned to each other.10.

An alternator is to be used for generation purpose in an aircraft. The most suited operating frequency of the alternator should be _ a) of 400 Hz to remove extra bulk b) of 400 Hz to reduce losses c) of 50 Hz to remove extra bulk d) none of the mentioned View Answer Answer: a Explanation: The components to be used in aircrafts are made to operate at very high frequencies so that the size of the components to be used is reduced.11.

A 3-phase synchronous alternator is connected to the infinite bus is over excited, that corresponds to _ a) capacitor b) inductor c) variable inductor d) any of the mentioned View Answer Answer: a Explanation: As the machine is over excited, it will act as source of reactive power and it is positive.

Q=V (Ecos (delta)-V)/X. Sanfoundry Global Education & Learning Series – Electrical Machines. To practice all areas of Electrical Machines,, Next Steps:

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What are the types of motor?

Types of Motors and its practical application in real life We know there are generally two types of motors, AC motor, and DC motor. AC motors are flexible for speed control and demand low power during start. On the other hand, DC motors are widely used due to its initial cost of low power units is less compared to AC and can be easily installed.

Why are universal motors so named?

Advantages and Disadvantages of Universal Motors Though they are not explicitly named for their widespread use, universal motors can, in fact, be found just about everywhere. Open any number of household appliances or industrial machines for example, and chances are you will find a universal motor at its core.

But if they aren’t named for the seemingly “universal” applications to which they lend themselves, why are they named as such? To put it simply, universal motors are so named because they can run on both alternate current (AC) and direct current (DC), meaning the “universal” namesake refers to their power supply options.

Having said all of that, the purpose of this article is not to delve into the origin of the term, “universal motor”, but rather to explore what makes this type of motor different from others as well as the various pros and cons of using one.

What is a universal set Mcq?

Mathematics Questions and Answers – Universal Set This set of Mathematics Multiple Choice Questions & Answers (MCQs) focuses on “Universal Set”.1. A set which is superset of all basic sets of that type? a) Power set b) Universal set c) Empty set d) Singleton set View Answer Answer: b Explanation: Universal set is the set which is a superset of all basic sets of that type.

Power set is the set of all subsets of given set. Empty set is the set which does not contain any element. Singleton set is the set that contains one element.2. Which of the following is universal set for integers? a) Natural numbers b) Whole numbers c) Rational numbers d) Prime numbers View Answer Answer: c Explanation: Since set of rational numbers is superset for set of integers so it can be a universal set for integers.

Rest are subset of integers so they can not act as the universal set for set of integers.3. Let A=, B=, C=, Which of the following may be considered as the universal set for set A, B, C? a) b) c) d) View Answer Answer: d Explanation: Universal set is the set which is superset of all basic sets of that type.

is the set which contains all the elements of set A, B, C.4. Which of the following is a universal set for the equilateral triangle? a) Set of isosceles triangles b) Set of right triangles c) Set of acute triangles d) Set of obtuse triangles View Answer Answer: a Explanation: Set of isosceles triangles can be considered as universal set for set of equilateral triangles because all equilateral triangles are isosceles.5.

Which of the following is considered as universal set for squares? a) Set of Rhombus b) Set of Parallelogram c) Set of Rectangle d) Set of Trapezium View Answer Answer: c Explanation: Set of rectangles is considered as universal set for set of squares because all squares are rectangles.

Check this: | 6. Which of the following is universal set for ? a) Set of vowels b) Set of consonants c) Set of letters of English alphabet d) Set of numbers View Answer Answer: c Explanation: Set of letters of English alphabet can be considered as universal set for because ‘a’ is a vowel and ‘p’ is a consonant.7.

Which of the following is considered as universal set for set of multiple of 4? a) Set of multiple of 16 b) Set of multiple of 12 c) Set of multiple of 2 d) Set of multiple of 8 View Answer Answer: c Explanation: Since every multiple of 4 is a multiple of 2 so, set of multiple of 2 is considered a set of multiple of 4.8.

U =, Which of the following is not a subset of the universal set? a) b) c) d) View Answer Answer: d Explanation: In, 10 is not present in set U. So, it is not the subset of universal set. Rest all are subsets of set U as their elements are present in universal set.9. The set is a universal set for a set of vowels.

a) True b) False View Answer Answer: a Explanation: Since set has all the vowels so it can be considered as the universal set for set of vowels.10. The set of prime numbers is a universal set for odd numbers. a) True b) False View Answer Answer: b Explanation: Since every prime number is not odd as 2 is even prime number so set of prime numbers can not be considered as universal set for a set of odd numbers.

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Which type of motor is used in electric vehicles Mcq?

Mainly, 2 types of motors are used in electric cars: DC motor and AC motor.

Which of the following is true for a universal motor?

A universal motor is categorized under a commutator type motor. In order to overcome the drawbacks of operation with AC supply, some modifications are made in a DC series motor so that it can work even on the AC current.

Can a universal motor run on AC and DC?

What Makes a Motor “Universal”? In the world of motors, one of the most-used designs is called the universal motor. Basically, these motors are wound-field DC motors, where the armature and field are in series, and the current is switched using a commutator and brushes.

But what makes it “universal?” Universal motors will run on either AC or DC current. While the ability to run on either AC or DC is inherent, it is generally not a deciding factor for product designers. Typically, designers are more concerned about the voltage level. Low voltage appliances (12, 24, 36v) that use batteries to run are typically DC.

High voltage motors (120v, 220/230/240v) that run from the power grid are typically AC. But at a given voltage, the universal motor can handle either. What Makes Universal Motors Popular?

Price. They are relatively inexpensive to manufacture because they have no electronic control boards. Output Power. They deliver about the highest amount of output power per pound of active material, iron and copper. High Starting Torque. They do not require capacitors or other circuits in order to start. Speed-Torque Curve. They have a downward sloping speed-torque curve, with speed increasing rapidly as the motor unloads. This makes them very well-suited for air moving applications, especially vacuum cleaners and pressure sprayers. In vacuum cleaners, this speed increase with decreasing load helps to compensate for dust filters as they clog up, allowing the appliance to maintain performance for longer. Simplicity. They are simple to wire up, as the motor itself does not have a polarity. If you do have colored leads, follow normal wiring conventions. (The motor may have a thermal protector, which should always be on the hot lead). But the motor itself does not care.

Life The life span for universal motors varies widely depending on the application, design and power level, between 50 and 3,000 hours. These motors use carbon brushes and commutators as sliding switches to deliver power to the armature coils as the motor rotates.

The carbon brushes do erode with time due to mechanical friction and electrical wear. Brushes can be service items depending on how the manufacturer designs the product. Because the commutator also wears some during life, universal motors cannot be rebrushed indefinitely. Usually a second set of brushes will get about half the life of the original.

Other components can also fail; bearings, electrical opens or shorts, and mechanical components. But if the motor is kept clean and vibration is not severe, these are relatively rare failure modes. AMETEK DFS universal motors have a number of innovative brush features; special material grades, custom brush mechanisms and the patented Eternity curved brush to enhance life.

Moving Air As mentioned above, one of the most popular uses for universal motors is in vacuum motors and blowers. In this case, the shaft is coupled to one or more fans or blower wheels. You may have noticed that new vacuum cleaner motors are much smaller and more compact than old ones. This is a trend in the vacuum motor industry.

Remember a little motor theory: OUTPUT POWER = OUTPUT SPEED x TORQUE If you can raise the speed, you can get the same output power with less torque. And torque translates directly into material. As a result, today’s vacuum motor probably runs twice as fast as your grandmother’s and is much smaller and lighter.

But to be able to do this, motor manufacturers have had to develop better bearings, commutators, brushes and fans that can handle the high speeds. They have also upped their game when designing the motor steel punchings to be more efficient in delivering speed and torque tailored to the needs of the market.

Manufacturers of air moving motors such as AMETEK DFS have taken advantage of these universal motor characteristics to supply a wide range of options, delivering a combination of motor air performance, size, weight, life and cost. Fan systems from one to six stages are available to meet a range of airflow and pressure/vacuum targets. Shaft Drive Some applications require a mechanical connection to the outside world to deliver power to another shaft, like a pulley or a cog. Or it may operate a load on the shaft that the operator does not want to run too fast; think of a string trimmer or a power tool.

• The universal motor has still been able to reduce weight and cost using more efficient punchings and higher temperature insulating materials that will hold up with less copper to dissipate heat.
• Speed Control The speed of a universal motor varies with the voltage.
• In special setups, you can use a variable AC transformer (“variac”) to adjust the performance for bench use.

(NOTE: Do not exceed the rated voltage on the motor. Shortened life or motor damage may occur.) For a more permanent solution, a TRIAC can be used along with a variable resistor or potentiometer to provide speed control by notching the wave form. This is effective for controlling speed, but it also shortens brush life.

1. Other methods such as pulse width modulated DC voltage can also be used.
2. In some cases the motor field can be wound to permit a low speed, either by switching the field coils — from in series with each other to in parallel — or by putting a fixed tap in the field that can switch the strength of the magnetic field and vary the performance.

Environment Universal motors come in many mechanical designs. All need to isolate the electrical part of the motor from environmental debris and moisture. They need clean air to cool the coils. Improper cooling is a frequent contributor to shortened life.

Some universal motors, called through-flow motors, are cooled by the working air. Others, called bypass motors, have a separate cooling fan which routes different air through the motor and across the coils. The working air bypasses the electrical side of the motor. They are the design of choice if the fan system is exposed to moist air.

When providing cooling air for bypass motors, the product designer must be careful not to recirculate cooling air that could build up heat with each pass through the system. The motor manufacturer typically has an application note for this purpose. If the motor is used in a vacuum cleaner application, it should be filtered before passing through the fan system, unless specifically designed to pass dirt and debris.

1. If dust or debris sticks to fan blades, it can build up unevenly and cause vibration.
2. High vibration can cause the brushes to bounce and arc, shortening brush life and damaging the commutator.
3. It can also damage the bearings.
4. Conclusion Universal motors definitely have a place in a variety of applications.

Before simply plugging in a universal motor, it’s important to understand what the application needs from the motor, and how the motor will react in certain environments. At AMETEK Dynamic Fluid Solutions, we understand you’re looking for more than just an off-the-shelf part or one-time solution.

What is a DC type motor?

Workings of a brushed electric motor with a two-pole rotor (armature) and permanent magnet stator. “N” and “S” designate polarities on the inside axis faces of the magnets ; the outside faces have opposite polarities. The + and – signs show where the DC current is applied to the commutator which supplies current to the armature coils The Pennsylvania Railroad’s class DD1 locomotive running gear was a semi-permanently coupled pairing of third rail direct current electric locomotive motors built for the railroad’s initial New York-area electrification when steam locomotives were banned in the city (locomotive cab removed here).

A DC motor is any of a class of rotary electrical motors that converts direct current (DC) electrical energy into mechanical energy. The most common types rely on the forces produced by induced magnetic fields due to flowing current in the coil. Nearly all types of DC motors have some internal mechanism, either electromechanical or electronic, to periodically change the direction of current in part of the motor.

DC motors were the first form of motors widely used, as they could be powered from existing direct-current lighting power distribution systems. A DC motor’s speed can be controlled over a wide range, using either a variable supply voltage or by changing the strength of current in its field windings.

Small DC motors are used in tools, toys, and appliances. The universal motor, a lightweight brushed motor used for portable power tools and appliances can operate on direct current and alternating current. Larger DC motors are currently used in propulsion of electric vehicles, elevator and hoists, and in drives for steel rolling mills.

The advent of power electronics has made replacement of DC motors with AC motors possible in many applications.

How do you tell if a motor is a universal motor?

How Can You Tell if a Motor is Universal? – Look for the construction of the stator core and the rotor. If there is no commutator, the motor is classified as an alternating current motor. If a commutator and brushes are present, the motor can be classified as either a DC or an AC motor ( Universal motor ).

How can you tell if a motor is universal?

Video Transcript – Welcome back, this is Joe and I’m Janette with Groschopp. In this fourth video in our series “How to Choose an Electric Motor,” we’ll begin discussing our four motor types —Universal, Permanent Magnet DC, AC Induction and Brushless DC.

• Throughout these videos, we’ll go over their construction, characteristics, advantages and disadvantages, as well as teach you how to interpret the motor performance curves for speed, torque and efficiency.
• There will be trade-offs between the different motor types and sometimes the best choice isn’t obvious.

That’s why we’ll give you some aids to help you understand the pros and cons to make the selection process easier. Janette, do you want to start us off with universal motors? Sure Joe. Universal motors are great for AC or DC applications that need a simple, high speed, low-cost motor with intermittent duty cycles.

1. They’re durable and suited for rough, high vibration applications where low noise is not needed, such as commercial concrete drills or floor sanders.
2. As you can see, we have the basic components of a Universal Motor laid out here.
3. Both the armature and field in this type of a motor are wound with magnet wire, and the electrical connection to the armature is made through the commutator and brushes.

There are two characteristics that set the Universal Motor apart from most other motor types. First, it runs off of both AC and DC power, giving it the name Universal Motor. Second, a Universal motor is capable of running at extremely high speeds, from 8,000 to more than 20,000 rpm.

1. These two characteristics make the universal motor fairly unique and ideally suited to specialized applications.
2. Several other characteristics of the universal motor to consider are the high starting torque; the 55 to 70 percent efficiency rate; and the average life expectancy of 500-2000 hours.
3. One main advantage of the Universal motor is its high power density.

It’s not uncommon for a Universal Motor to have over twice the continuous output power as an equally-sized AC motor. Additionally, its low cost, portability, and ability to run without a control make it worth looking at. A few downsides to universal motors are that they are noisy, inefficient at low voltages, burnout quickly in stall conditions, require high maintenance due to the brushes and the open frame design.

• They also have poor speed regulation, and the high speeds prevent gearbox usage.
• That’s right, Janette.
• Before we look at universal motor performance curves, I’d like to quickly comment on low voltage and Universal Motors.
• If you operate a Universal Motor under 100 volts, the efficiency drops drastically.

With a battery input source, the universal motor could quickly drain it. As a rule, other motor options should be considered for low voltage situations. Here we have the typical speed-torque curve of the Universal Motor. This is the cold motor curve, and you can see that it’s fairly linear with good starting torque.

The sharp upward curve as the torque decreases is a unique characteristic of the universal motor. Now we’ve added the hot motor curve. Here you can see the effect that heat has on motor performance. For a given torque point, the motor will run a little slower as it heats up. Alrightnow we’ve added the motor’s efficiency curve, the black dashed line.

Under ideal circumstances, the motor’s peak efficiency will occur very near the motor’s operating torque. However, in most cases the actual peak efficiency will occur at a higher torque than the rated torque. Janette, I’d just like to make a comment about speed torque curves.

Nehru Baral