Motors

Question 1

What happens to slip speed as load is added

Answer 1

The slip speed increases

Question 2

Do motors with higher full load rotor speeds have higher or lower percent speed regulation?

Answer 2

Lower speed regulation %

Question 3

Do motors with higher full load rotor speeds have higher or lower percent efficiency?

Answer 3

Higher efficiency

Question 4

Which rotor parameter stays constant

Answer 4

Resistance

Question 5

Which rotor parameter is proportional to rotor speed?

Answer 5

Power factor of the rotor

Pf(r)

Question 6

Which five rotor parameters increase with slip speed?

Answer 6

EZfIX
Voltage
Impedance
Frequency
Current
Reactance

Question 7

What is the formula to find voltage of the rotor

Answer 7

Er = Ebr x s

Question 8

Which rotor parameters are directly proportional to slip speed

Answer 8

Frequency, reactance and voltage

Question 9

What does I r(R) represent

Answer 9

Active, in phase, horizontal or resistive current in the rotor

Question 10

What is breakdown or pullout torque

Answer 10

The point at which max torque is reached and any added load causes the motor to stall.

Question 11

State the formulas to find breakdown torque

Answer 11

Rr = Xr 
Ir(R) = Ir(x)
pf(r) = .707 or cos45*
0theta(r) = 45*

Question 12

If mechanical load is reduced slip speed will do what

Answer 12

Decrease

Question 13

If mechanical load is increased then what will happen to %slip?

Answer 13

Increase

Question 14

As slip speed increases, what will happen to rotor speed?

Answer 14

Rotor speed decreases

Question 15

If mechanical load is increased what will happen to the impedance of the rotor (Zr)?

Answer 15

Z(r) increases

Question 16

Within normal range, as load is increased, what will happen to rotor torque

Answer 16

Torque increases

Question 17

As load is decreased what will happen to rotor voltage

Answer 17

Deceases

Slip goes does down as load decreases, voltage is proportional to slip

Question 18

As load is increased what will happen to reactance of the rotor

Answer 18

Rotor reactance will increase

Question 19

As slip is decreased what will happen to the power factor of the rotor?

Answer 19

Power factor will increase

Question 20

As load is increased what will happen to rotor resistance

Answer 20

It will stay the same because it is conctant

Question 21

As load is increased from no load to full load, the stator current will do what

Answer 21

Increase

Question 22

As load increase, motor current will do what

Answer 22

Increase

Question 23

Is motor current directly proportional to power and torque?

Answer 23

No, but it will increase with them

Question 24

Is torque directly proportional to slip?

Answer 24

Yes

Question 25

Is mechanical power output directly proportional to slip

Answer 25

Yes

Question 26

What causes torque in a motor

Answer 26

The interaction of the rotor in the stator fields

Question 27

What is another name for breakdown torque?

Answer 27

Pullout torque

Question 28

Both nema A and B design rotors produce a max torque of what percent of sync speed?

Answer 28

75-80%