# Induction Motor Slip decrease with frequency decrease for same load.

• Physicist3
In summary, the amount of slip in an induction motor decreases with frequency under the same load conditions. This is due to the decrease in iron losses and no-load current, as well as the proportional decrease in ventilation and friction-bearing losses with the square of RPM. The decrease in mechanical power required to maintain the rotor in rotation also results in less slip.
Physicist3
Hi,

Does anyone know or could help me understand the reasoning for the amount of slip within an induction motor decreasing with frequency under the same load conditions? I.e. For no external load, the slip is higher at 50Hz than at 20Hz etc? Thanks

Is windage proportional to speed2 or to speed3 ?

“No-load” it does not mean “no load at all”. There are no-load losses –iron losses, ventilation and friction-bearing losses and copper losses. The no-load current-mainly reactive-is about 30% of rated and copper [winding] losses could be elevated. As jim hardy already said, ventilation and friction are proportional with square of rpm, so less frequency less rpm [rpm=60*freq/p where p= no.of pole pairs] less slip. The iron losses decrease with the frequency and so the no-load current and in turn no-load copper losses. The mechanical power requested in order to maintain the rotor in rotation will decrease even if the torque remains constant P=T*(2*PI()*Freq:
$P=T\omega=2\pi_fT$
Less power less slip.

## 1. Why does the slip of an induction motor decrease with a decrease in frequency for the same load?

The slip of an induction motor is the difference between the synchronous speed and the actual speed of the rotor. As frequency decreases, the synchronous speed also decreases. This means that there is a smaller difference between the synchronous speed and the actual speed, resulting in a decrease in slip.

## 2. How does a decrease in frequency affect the speed of an induction motor?

A decrease in frequency results in a decrease in the speed of an induction motor. This is because the frequency of the power supply determines the synchronous speed of the motor. As the frequency decreases, the synchronous speed also decreases, resulting in a slower speed for the motor.

## 3. Is there a limit to how much the slip can decrease with a decrease in frequency?

Yes, there is a limit to how much the slip can decrease with a decrease in frequency. This is because the motor still needs a certain amount of slip to produce torque. If the slip decreases too much, the motor will not be able to produce enough torque to maintain the desired speed.

## 4. Can the slip of an induction motor be decreased without changing the frequency?

Yes, the slip of an induction motor can be decreased without changing the frequency by changing the load on the motor. A decrease in load will result in a decrease in slip, as the motor does not need to work as hard to maintain the desired speed.

## 5. What other factors can affect the slip of an induction motor?

Aside from frequency and load, other factors that can affect the slip of an induction motor include the design and construction of the motor, as well as the type and condition of the rotor and stator. Environmental conditions, such as temperature, can also impact the slip of the motor.

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