3 phase motors principles

What type of supply is connected to a 3 phase motor?

• ac

• dc

• neither, it's a generator

Which part in a 3 phase motor provides the motion in the drive shaft?

• Armature

• Stator

• Rotor

• Field winding

In a 3 phase motor, where is the rotating magnetic field produced?

• Rotor

• Stator

• Armature

The speed of the RMF is symbolised by the letters

• n_r

• n_s

• f

• rms

The speed of the motor is symbolised by the letter?

• n_r

• n_s

• f

• rpm

In the equation to calculate the synchronous speed the letter 'p' denotes the

• number of poles

• number of pole pairs

• number of primary poles

• voltage on the primary

The equation used to calculate the speed of the RMF is?

• $n_s=\frac{f}{p}$

• $n_s=\frac{p}{f}$

• $n_r=\frac{f}{p}$

• $n_r=\frac{p}{f}$

The slip of a motor is the

• difference between the synchronous speed and he pole pairs

• efficiency of the motor

• difference between the pole pairs and the frequency

• difference between the rotor speed and the synchronous speed

The equation used to calculate the per unit slip is

• $\frac{n_s-n_r}{n_s}\ x\ 100$

• $\frac{n_r-n_s}{n_r}$

• $\frac{n_r-n_s}{n_r}x\ 100$

• $\frac{n_s-n_r}{n_s}$

If the synchronous speed of a 3 phase motor is 120rpm and the slip is 3%, what is the rotor speed?

• 3.6rpm

• 116.4rpm

• 4000rps

• 123.6rpm