Question 1

In a shunt motor, the current flows from the positive power supply terminal through the shunt winding to the negative power supply terminal, with s similar current path through the armature winding.

Accepted Answer

In a shunt motor, the current flows through the shunt winding and the armature winding in parallel, from the positive power supply terminal to the negative power supply terminal.

Question 2

The cemf produced in a shunt motor has no effect on the magnetic field of the shunt windings.

Accepted Answer

The counter electromotive force (cemf) in a shunt motor affects the armature circuit but does not directly influence the magnetic field produced by the shunt windings, which are connected in parallel and maintain a constant field.

Question 3

The speed of a shunt motor can be controlled beyond its rated value by changing the amount of voltage across either the field or the armature winding.

Accepted Answer

The speed of a shunt motor can be controlled by varying the voltage across its field winding to change the field current, or by adjusting the voltage applied to the armature winding. Reducing field current or increasing armature voltage can increase the motor's speed beyond its rated value.

Question 4

The short shunt cumulative compound motor is used most often because the shunt field has a relatively constant current.

Accepted Answer

The short shunt compound motor connects the shunt field across the armature only, not because the shunt field has a relatively constant current, but because this configuration allows for a combination of series and shunt characteristics, improving starting torque while maintaining good speed regulation.

Question 5

The differential compound motor and the cumulative compound motor are the same except the connection to the shunt field terminals.

Accepted Answer

The differential compound motor has the shunt field connected in series opposition to the armature, while the cumulative compound motor has the shunt field connected in series aiding to the armature.

Question 6

If the polarity of the interpole winding is not matched to the polarity of the shunt field winding, the motor will overheat.

Accepted Answer

The answer of If the polarity of the interpole winding...

Question 7

The speed of the compound motors can be controlled with an adjustment to the shunt winding current.

Accepted Answer

Adjusting the shunt winding current in compound motors allows for the control of their speed because it changes the magnetic flux in the shunt field, which in turn affects the motor's speed.

Question 8

Solid state devices like the H -bridge eliminate shoot -through.

Accepted Answer

H-bridge is a solid-state device that uses four switches to control the direction of current flow through a load. The switches are arranged in a way that prevents shoot-through, which is a condition where current flows through both switches in the same direction.

Question 9

In a thyristor drive, the SCR controls the amount of current that flows through the armature of a DC motor.

Accepted Answer

In a thyristor drive, the Silicon Controlled Rectifier (SCR) is used to control the amount of current flowing through the armature of a DC motor, thereby controlling the motor's speed and torque.

Question 10

The magnetic field strength of an electromagnet cannot be increased by
A) the amount of current.
B) the type of core.
C) the type of material.
D) the number of coils in the wire.

Accepted Answer

The magnetic field strength of an electromagnet can be increased by adjusting the amount of current flowing through the wire, the type of core material (usually a ferromagnetic material enhances the field), and the number of coils or turns in the wire. The "type of material" mentioned in option C is ambiguous because it does not specify whether it's referring to the core material or the wire material. However, in the context of increasing magnetic field strength, the material of the wire (assuming it's a conductor) does not significantly affect the strength of the magnetic field compared to the other factors listed. The core material, current, and coil turns are directly related to the magnetic field's strength, making C the least relevant to directly increasing magnetic field strength.

Question 11

Which of the following is the same in the DC series motor and the universal motor?
A) Field strength
B) Iron core composition
C) No -load speeds
D) Input power

Accepted Answer

The answer of Which of the following is the same...

Question 12

The speed of a shunt motor can be controlled by
A) varying the armature current.
B) varying the field current.
C) varying the voltage across the field winding.
D) A and C
E) all of the above

Accepted Answer

The speed of a shunt motor can be controlled by varying the armature current, varying the field current, and varying the voltage across the field winding. All these methods affect the motor's speed by altering the magnetic flux or the current in the circuit, which in turn changes the speed.

Question 13

Which of the following is not a type of compound motor?
A) Interpole
B) Integrator
C) Differential
D) Cumulative

Accepted Answer

Integrator is not a type of compound motor. Compound motors include interpole, differential, and cumulative types, which are variations based on how the windings are connected. Integrator, however, does not refer to a motor type but rather to a function or device in electronics and control systems for integrating signals.

Question 14

Which of the following is not a component of a DC motor starter?
A) Arc quencher
B) Contactor
C) Overload relay
D) Heater
E) Braking relay

Accepted Answer

The answer of Which of the following is not a...

Question 15

Match the overload block with its operation.
-Eutectic
A) Uses dissimilar materials
B) Uses motor voltage
C) Uses motor current
D) Uses melting poin

Accepted Answer

A eutectic overload block operates based on the melting point of a eutectic alloy, which melts at a specific temperature to break the circuit and protect the motor.

Question 16

Match the overload block with its operation.
-Bimetallic
A) Uses dissimilar materials
B) Uses motor voltage
C) Uses motor current
D) Uses melting poin

Accepted Answer

Bimetallic overload blocks use dissimilar materials that expand at different rates to trip the circuit when overheated.

Question 17

Match the overload block with its operation.
-Phase loss
A) Uses dissimilar materials
B) Uses motor voltage
C) Uses motor current
D) Uses melting poin

Accepted Answer

Phase loss is detected by monitoring the motor current, as a loss of phase will cause an imbalance in the current.

Question 18

Match the technique t o the component i t uses for braking,
-Dynamic
A) Resistor
B) Inductor
C) Power supply

Accepted Answer

Dynamic braking involves converting the kinetic energy of the motor into electrical energy, which is then dissipated as heat through a resistor.

Question 19

Match the technique t o the component i t uses for braking,
-Regenerative
A) Resistor
B) Inductor
C) Power supply

Accepted Answer

Regenerative braking involves converting the kinetic energy of the vehicle back into electrical energy, which can then be stored and reused. This process uses the vehicle's power supply or battery to store the energy recovered during braking.

Question 20

Match the technique t o the component i t uses for braking,
-Plugging
A) Resistor
B) Inductor
C) Power supply

Accepted Answer

Plugging involves reversing the motor's connections to the power supply, effectively using the power supply to brake the motor.

Quiz 5: DC Motors, Control Circuits, AC Motors and Variable Speed Drives

In a shunt motor, the current flows from the positive power supply terminal through the shunt winding to the negative power supply terminal, with s similar current path through the armature winding.

The cemf produced in a shunt motor has no effect on the magnetic field of the shunt windings.

The speed of a shunt motor can be controlled beyond its rated value by changing the amount of voltage across either the field or the armature winding.

The short shunt cumulative compound motor is used most often because the shunt field has a relatively constant current.

The differential compound motor and the cumulative compound motor are the same except the connection to the shunt field terminals.

If the polarity of the interpole winding is not matched to the polarity of the shunt field winding, the motor will overheat.

The speed of the compound motors can be controlled with an adjustment to the shunt winding current.

Solid state devices like the H -bridge eliminate shoot -through.

In a thyristor drive, the SCR controls the amount of current that flows through the armature of a DC motor.

The magnetic field strength of an electromagnet cannot be increased by

Which of the following is the same in the DC series motor and the universal motor?

The speed of a shunt motor can be controlled by

Which of the following is not a type of compound motor?

Which of the following is not a component of a DC motor starter?

Match the overload block with its operation. -Eutectic

Match the overload block with its operation. -Bimetallic

Match the overload block with its operation. -Phase loss

Match the technique t o the component i t uses for braking, -Dynamic

Match the technique t o the component i t uses for braking, -Regenerative

Match the technique t o the component i t uses for braking, -Plugging