# motor slip vs rotational speed

In Induction motor theory the term slip is used as normalized relative speed of the rotor to the synchronous speed and it depends on the physical rotational speed of the rotor.

Is there any special benefit of not using the physical observable rotational speed in the formulas and instead invent another special term 'slip' to be used in the motor modeling formulas?

Will i lose any generalization if i convert the formulas from the 'slip' parameter to the rotational speed parameter?

• You need to explain which formulas you're asking about if you want an answer. Slip means exactly what it means. It expresses the difference between two rotational speeds as you've been taught. It changes from moment to moment depending on load countertorque, so it is likely that in almost every case, your special term would need to be a formula and couldn't be expressed with a constant. That said, what is it you want to use it for? Show the formulas and explain how you'd like to work slip into them. If you're just missing the next set of formulas you need someone can help. – K H Dec 29 '18 at 3:49

## 1 Answer

Slip is not a special term, it is essential to the development of torque by an induction motor. The induction motor equivalent circuit is developed based on using per-unit slip to show the conversion of electrical energy to mechanical energy. Many calculations would be more complex if rotational speed were to be used. There are situations in which it is more appropriate to use speed in radians per second or revolutions per minute. As you work through various derivations and calculations, it should be apparent which is most appropriate. Note that some formulae use both slip and speed. That may seem awkward, but if you look closely at the formula, you will see that using per-unit slip simplifies the formula.