Flashcards in Motors Deck (75)
What happens to slip speed as load is added
The slip speed increases
Do motors with higher full load rotor speeds have higher or lower percent speed regulation?
Lower speed regulation %
Do motors with higher full load rotor speeds have higher or lower percent efficiency?
Which rotor parameter stays constant
Which rotor parameter is proportional to rotor speed?
Power factor of the rotor
Which five rotor parameters increase with slip speed?
What is the formula to find voltage of the rotor
Er = Ebr x s
Which rotor parameters are directly proportional to slip speed
Frequency, reactance and voltage
What does I r(R) represent
Active, in phase, horizontal or resistive current in the rotor
What is breakdown or pullout torque
The point at which max torque is reached and any added load causes the motor to stall.
State the formulas to find breakdown torque
Rr = Xr
Ir(R) = Ir(x)
pf(r) = .707 or cos45*
0theta(r) = 45*
If mechanical load is reduced slip speed will do what
If mechanical load is increased then what will happen to %slip?
As slip speed increases, what will happen to rotor speed?
Rotor speed decreases
If mechanical load is increased what will happen to the impedance of the rotor (Zr)?
Within normal range, as load is increased, what will happen to rotor torque
As load is decreased what will happen to rotor voltage
Slip goes does down as load decreases, voltage is proportional to slip
As load is increased what will happen to reactance of the rotor
Rotor reactance will increase
As slip is decreased what will happen to the power factor of the rotor?
Power factor will increase
As load is increased what will happen to rotor resistance
It will stay the same because it is conctant
As load is increased from no load to full load, the stator current will do what
As load increase, motor current will do what
Is motor current directly proportional to power and torque?
No, but it will increase with them
Is torque directly proportional to slip?
Is mechanical power output directly proportional to slip
What causes torque in a motor
The interaction of the rotor in the stator fields
What is another name for breakdown torque?
Both nema A and B design rotors produce a max torque of what percent of sync speed?
The rotor winding ms of a WRM are brought out and connected to what?