A 5hp 400v 4 pole 50hz induction motor has 36 slots in stator and 40 slots in rotor may crawl synchronously at which speed?

Question

Answer

We know that synchronous speed Ns=120f/p
here we have frequency (f)=50Hz&p=4
then we get the answer as 1500rpm

Answer

Speed of a 5hp 400v 4 pole 50hz induction motor with 36 slots in stator and 40 slots in rotor

Motor Specifications

Power rating: 5hp

Voltage rating: 400V

Pole pairs: 4

Frequency: 50Hz

Stator slots: 36

Rotor slots: 40

Synchronous Speed Formula

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

Synchronous speed (n_s) = (120 x frequency) / number of pole pairs

Calculations

Substituting the given values in the formula:

Synchronous speed (n_s) = (120 x 50) / 4 = 1500 rpm

Crawling Speed

If the number of rotor slots is not an exact multiple of the number of stator slots, then the motor may crawl or move slowly at certain speeds. This phenomenon is known as crawling.

Since the number of rotor slots (40) is greater than the number of stator slots (36), the motor may experience crawling. The crawling speed can be calculated as:

Crawling speed = synchronous speed / (1 + (s / 120)), where s is the slip

At the crawling speed, the rotor will move in small steps instead of rotating smoothly. The crawling speed of the motor can be avoided by using a different number of rotor or stator slots that are in an exact multiple of each other.

Conclusion

The synchronous speed of the 5hp 400v 4 pole 50hz induction motor with 36 slots in stator and 40 slots in rotor is 1500 rpm. However, the motor may experience crawling due to the mismatch in the number of stator and rotor slots.

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