Explainer video · TEMISA

Induction motor slip: why a 4-pole motor never reaches 1,800 rpm

Short answer

Slip is the difference between the stator field speed and the rotor speed. At 60 Hz the field of a 4-pole motor turns at 1,800 rpm and the rotor always a little slower: that difference lets the field cut the bars, induce current and make torque. With overload or low voltage slip grows, current rises and the winding heats.

Key points

At 60 Hz the field of a 4-pole motor turns at 1,800 rpm.
The rotor always turns a little slower: that difference is slip.
Without slip the field doesn't cut the bars and there is no torque.
Overload or low voltage increases slip, current and winding temperature.
Current is checked against the nameplate.

Transcript

Why does a 4-pole motor never reach 1,800 RPM? It's not a defect, it's the key. At 60 Hz, the stator field spins at 1,800, and the rotor always chases it a little slower. Like pushing a swing: if your hand moves at the same speed, you're not pushing anymore. That difference is slip: the field cuts the rotor bars, induces current and makes the force. But careful, with overload or low voltage, slip grows, current rises and the winding heats up. That's why current is checked against the nameplate. So it's not missing speed, it needs it. Is yours slower than its nameplate? Comment SLIP and we'll tell you what to check.

Frequently asked questions

Why doesn't a 4-pole motor run at 1,800 rpm?

It needs slip: if the rotor caught the field, the field would stop cutting the bars and there would be no torque.

When is slip a problem?

When it grows from overload or low voltage: current rises and the winding heats.

How is it checked?

By measuring current against the nameplate. TEMISA tests and repairs motors; email ventas@temisa.mx.

Video with images and narration generated with AI.

See the service: Induction motor repair

Request a quotation by email: ventas@temisa.mx. Phone: +52 33 3614 2460.