Rotation speed electric motors

Electric motors: theoretical rotation speed determined by the number of poles

Rotation speed electric motors

Welcome to this guide created by Itieffe, dedicated to electric motors and their theoretical rotation speed determined by the number of poles. This fundamental aspect of electric motors directly influences their performance and practical application in a wide range of industrial and technological sectors.

The importance of speed in electric motors

Rotational speed is one of the key characteristics of electric motors and has a significant impact on their performance.

Understanding how this speed is affected by the number of poles in the motor is essential for engineers, technicians and professionals in fields such as industrial automation, mechanical engineering and electronics.

Objectives of the Guide

This guide was created with the aim of providing a complete overview of the following aspects:

Number of poles and rotation speed: we will explore the relationship between the number of poles of a motor and its vetheoretical rotation speed. We will explain how to calculate this speed and how this knowledge can be applied in practice.
Practical Applications: We'll illustrate how understanding this concept is crucial in a number of industries, including mechanical engineering, manufacturing, and more.
Design Considerations: We will discuss how this concept will impact the design and selection of electric motors to meet specific application needs.
Theoretical rotation speed: we will delve into the concept of theoretical rotation speed of electric motors and explain how it is influenced by the number of poles in the motor.

Electric motors speed - Poles

The speed of an AC three-phase asynchronous motor is directly related to the frequency of the power supply network and the number of poles:

ns = (2 xfx 60) / p

where:

ns = synchronous speed

f = network frequency

p = number of poles (2 each polar pair)

The rotation speeds under load of asynchronous motors are slightly lower than the synchronism speed indicated in the table, due to the slip which is always less than 1.

For this a 4-pole 50 Hz motor will never make 1.500 revolutions but about 1.450.

Speed rpm

number of poles	50 Hz	60 Hz	100 Hz
2	3.000	3.600	6.000
4	1.500	1.800	3.000
6	1.000	1.200	2.000
8	750	900	1.500
10	600	720	1.200
12	500	600	1.000
16	375	450	750
20	300	360	600
24	250	300	500
32	187,5	225	375
48	125	150	250

(The values in this table are theoretical)

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