Question

1-what is the best choice of a single phase motor for compressor?
a) a shaded pole motor
b) a split phase motor
c) a capacitor start induction motor
d) a capacitor run induction motor
e) a permanent split capacitor motor

2- Stepper motors typically operate with:
a) A single phase
b) Three phases (X,Y and Z)
c) 4 phases
d) 2 phases ( A and B)
e) The number of phases varies with the motor design

3- A 200 step stepper motor:
a) Has 200 poles
b) Has 100 poles on 2 phases
c) Has 4 poles on each of 2 phases
d) is not commercially available
e) is too complex to manufacture

4- When a stepper motor moves from one step to another:
a) The motor may overshoot
b) There is no possibility of overshoot
c) The overshoot will not exceed 1/2 step
d) A and C but not B
e) All of the above

5- The controller in an industrial servo motor system:
a) Is universal, any controller will work with any motor
b) Is always sold with the motor
c) Must be match to the motor according to manufacturer's recommendation
d) A and B
e) B and C

6- Industrial servo motor:
a) are not capable of holding a fixed position
b) have a holding torque that hold a fixed position with no movement
c) hold a fixed position by making small corrections as the load moves, resulting in small oscillations
d) are better than a stepper motor of holding a fixed position
e) do not have enough torque that hold fixed positions with no movement

7-Limit switches can be used:
a) with stepper or servo systems
b) can be used to prevent machine over travel
c) can be used to automatically set the 0 point for a motor controller
d) B and C
e) A, B and C

8- Stepper motors of the same faceplate sizebut longer length:
a) offer no difference in performance
b) generally run at higher speed
c) are generally capabe of producing more torque
d) generally run at lower speed
e) generally run at longer period of time

9- For an intermittent load, such as a manual lathe, which method should be used to size the motor:

a) The motor’s nominal size should match the minimum load
b) The motor’s nominal size should match the RMS horsepower calculated based on the anticipated loads
c) The motor’s nominal size should match the maximum anticipated load
d) Any available motor can be used, the operator will adapt their work methods

10- A motor is running at 90% of its nameplate voltage. Compared to running under the same condition at 100% of name plate voltage you expect the temperature to:

a) Increase
b) Decrease
c) Remain the same

11- A motor is running at 90% of its nameplate voltage. Compared to running under the same condition at 100% of name plate voltage you expect the current to:
a) Increase
b) Decrease
c) Remain the same

12- A motor is running at 90% of its nameplate voltage. Compared to running under the same condition at 100% of name plate voltage you expect the speed to:
a) Increase
b) Decrease
c) Remain the same

13- A motor is running at 110% of its nameplate voltage. Compared to running under the same condition at 100% of name plate voltage you expect the starting torque to:
a) Increase
b) Decrease
c) Remain the same

14- Motors with the same NEMA frame size are:
a) Electrically interchangeable (identical voltage and current ratings)
b) Mechanically interchangeable (same mounting hole locations and shaft size)
c) Mechanically interchangeable (same speed and horsepower rating)
d) Both electrically and mechanically interchangeable
e) The same colour

15- Which is not a component of a DC motor:
a) Field Winding
b) Squirrel Cage Rotor
c) Armature winding
d) Brushes
e) Commutator

16- In a permanent magnet DC motor the magnets take the place of the:
a) field Winding
b) Armature Winding
c) Bearings

17- If the field coil of a DC shunt motor is opened, the armature speed will __________.
a) increase
b) decrease
c) stay the same
d) runaway
e) stop

18- The __________ DC motor has the highest starting torque.
a)series
b)shunt
c) additive compound
d) subtractive compound
e) long shunt

19- Which of the following factors determine the synchronous speed of an AC motor?
a) inductance of the rotor windings
b)the frequency of the applied voltage
c) the number of field poles per phase
d) the physical load driven by the motor
e) both b and c

20- Which of the following inductance motors use a centrifugal switch?

a) resistance-start, induction-run
b) capacitive-start, induction run
c) shaded pole
d) a and b
e) b and c

Answer 1

1. e

Permanant Split capacitor motor is best choice for the compressor.

• In this Capacitor is permanantly conneced to the motor. That single capacitor is used to start and run the motor.
• It has high efficiency.
• High power factor due to permanant capacitor.
• No centrifuse switch is requeired because the capacitor is always connected to the motor.

2. e) The number of phases varies with the motor design

• Stepper motor converts Electrical power into motion in the form of rotation. It can control the speed of the rotations.
• Stepper motor usually have two phases. But according to the motor design the number of phases will vary accordingly.

3. c) Has 4 poles on each of 2 phases

    A 2 phase stepper motor has 200 steps. The structure of rotor has 50 teeths. A two phase motor can have 4 poles. A rotor can complete 50 teeths for 1 pole and so that it can complete 200 teeth(200 steps) for 4 poles.

4. a) The motor may overshoot

The stepper motor moves from one step to another, the rotot does not stop immediately. when the rotor passes its Overshoot( Its final position), then goes to the opposit direction then moves back and forth finally reaches to rest position.

5. a) Is universal, any controller will work with any motor

Normally all types of motors rotate when power is ON and stops rotating when power goes OFF. But servo motor ratatesaccording to instructions which is given by microcontroller. Any controller can be programmed according to user requirement and interfaced to the servo motor.

6. e) do not have enough torque that hold fixed positions with no movement

The servo motor work with high speed and low torque. It try to rotate according to commands given by microcontroller. When it stopped because of its high speed and low torque, it continues to move back and forth.

7. e) A, B and C

Limit switch is used to control the coil of relays and motor starters in stepper motors and servo motors. The limit switch stops the motor from over travel and takes the rotor its starting position.