(A, B) Formulas

Question 1

An induction motor consists of

Answer 1

A stator and motor assembly

Question 2

The motor speed lags the….

Answer 2

Magnetic field speed

Question 3

Synchronous speed formula

Answer 3

ΠSYNC= (120 • f{Hz}) / NPOLES

Question 4

Slip speed formula

Answer 4

Ns = Nsyn - Nr
Ns = S x Nsyn

Nr = speed of rotor (r/min)

Question 5

Slip formula

Answer 5

S = Ns ÷ Nsyn

NS - slip speed

Question 6

Define rotor resistance

Answer 6

Rr (constant)

Question 7

rotor voltage formula

Answer 7

Er = S x Ebr

Ebr = blocked rotor

Question 8

Rotor frequency formula

Answer 8

Fr = S x Fbr

Fbr = 60

Question 9

rotor reactance formula

Answer 9

Xr = S x Xbr

Question 10

rotor impedance formula

Answer 10

Zr = squared root of Rr squared + Xr squared

Question 11

Rotor current formula

Answer 11

Ir = Er ÷ Zr

Question 12

Speed of rotor (rotational frequency)

Answer 12

Nr = Nsyn - ns

Question 13

Reactive rotor current formula

Answer 13

Ir(R) = Ir x Pfr

Producers torque
Is the only quantity that increases then decrease as rotor accelerates.

Question 14

define EZFIX

Answer 14

Induced voltage
Impedance
Frequency
Induced current
Inductive reactance

PF
Resistance

Question 15

Power factor formula

Answer 15

Rr ÷ Zr

Question 16

Torque formula (Nm)

Answer 16

T = F x r

T - tourque
F - force in newtons (N)
r - radius in meters

Question 17

Mechanical power formula

Also known as full load torque

Answer 17

P = T(fl) x n ÷ 9.55

P - power in watts
n - rotational speed / frequency in revolting per minute. (r / m)

Question 18

When mechanical power is required to be in horse power the formula is

Answer 18

Hp = T x n ÷ 7121

7121 is 9.65 x 746

Question 19

Motor Efficiency formula

Answer 19

P out ÷ p in

P out = hp x 746
P in = P out plus P losses (heat) or (V x FLA) full load current rating.

Question 20

1 hp = ___ kilowatt

Answer 20

0.746

Question 21

Motor % speed regulation formula

Answer 21

%nreg = n (nl) - n (fl) devided by (fl) x 100

n - speed
nl - no load r/min
fl - full load r/min
N full load = Nsyn - ns

Question 22

Permissible output power formula

Answer 22

Service factor x nameplate horse power

Question 23

Breakdown torque means

Answer 23

Rr = Xr

Question 24

Breakdown torque occurs at what pf?

Answer 24

0.707