Question

Motor AC Asynchronous 400 HP, 3 fasa, 8 kutub, slip 5 %, terminal input voltage of 380V, 50 Hz, what is the rotor speed at full load? what is the rotor speed if the frequency increase to 53 Hz?

Answer 1

The synchronous speed of the motor can be calculated using the formula:

Synchronous speed = (120 x Frequency) / Number of poles

Here, Frequency is given as 50 Hz and Number of poles is given as 8.

So, Synchronous speed = (120 x 50) / 8 = 750 rpm

The rotor speed at full load with a slip of 5% can be calculated as:

Rotor speed = (1 - Slip) x Synchronous speed

Slip is given as 5% or 0.05.

So, Rotor speed = (1 - 0.05) x 750 = 712.5 rpm

If the frequency increases to 53 Hz, the synchronous speed can be calculated as:

Synchronous speed = (120 x 53) / 8 = 795 rpm

Using the same slip value of 5%, the new rotor speed can be calculated as:

Rotor speed = (1 - 0.05) x 795 = 755.25 rpm