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3 Phase Motors

3 Phase Motors

Three phase AC motors are used prolifically within all varieties of industry. We supply motors from 0.75kW up to 315kW to our customers. Our team understands that delivery speed is often crucial; we are well used to supporting breakdowns and can offer delivery to the site on the same day if required.

Selecting a 3 Phase Motor Correctly:

Motor Size

When sizing a motor, there are two different aspects to take into account; the physical size and the motor's power rating. For the physical size, usually referred to as the frame size, please see the heading "IEC Framed Motors" below. For the power rating of the motor, continue reading below.

Motor Power

Motors are rated and selected to suit the application by their output power. This output is measured as standard in either kW (Kilowatts) or in HP (Horsepower). We have put together a useful conversion table below to help. 

 Kilowatts (kW) Horsepower (HP)
0.09kW 0.12HP
0.12kW 0.16HP
0.18kW 0.25HP
0.25kW 0.33HP
0.37kW 0.5HP
0.55kW 0.75HP
0.75kW 1HP
1.1kW 1.5HP
1.5kW 2HP
2.2kW 3HP
3kW 4HP
4kW 5.5HP
5.5kW 7.5HP
7.5kW 10HP
11kW 15HP
15kW 20HP
18.5kW 25HP
22kW 30HP
30kW 40HP
37kW 50HP
45kW 60HP
55kW 75HP
75kW 100HP
90kW 120HP
110kW 150HP
132kW 175HP
160kW 215HP
200kW 268HP
250kW 335HP
315kW 420HP


Motor Speed

3 Phase Motors are available in different speeds as standard. These speeds are a result of the number of poles contained inside the motor. These speeds are nominal and assume that the motor is 100% efficient, which is not possible. They should be used as a guide when selecting a suitable motor. 

This table gives you an idea of the nominal speeds for the number of poles within the motor.

 Number Of Motor Poles Nominal Speed (rpm)
2 Poles 3000rpm
4 Poles 1500rpm
6 Poles 1000rpm
8 Poles 800rpm


Motor Mounting Type

There are five standard mounts for AC motors utilising the IEC frame standard. These mounting types are referred to and illustrated below:


B3 - Foot Mount

B5 - Flange Mount

B14 - Face Mount

B34 - Foot Mount and Face Mount (Foot and Face)

B35 - Foot Mount and Flange Mount (Foot and Flange)

AC Motor Mount Types


Motor Body Material - Cast Iron or Aluminium?

You can select either an aluminium or cast iron frame for your motor. The aluminium frame is far lighter than its equivalent cast iron motor in the same frame size. Aluminium can also be less prone to corrosion, so if used in harsher climates or environments can be advantageous. Cast iron, on the other hand, can increase inductance and therefore offer slight advantages with efficiency. Its weight can be a significant consideration; aluminium may be better suited for applications such as boats or vehicles and the like.


Aluminium motors are available from Frame Size 56 to 132

Cast Iron motors are available from Frame Size 112 to 355


Motor Voltage

3 Phase motors are as standard 415v / 690v. The smaller motors can be supplied with windings in 240v / 415v or can be wound to the standard 415v /690v configuration. 


Paint finish

All of the motors supplied by Power Heating Plants are supplied as standard in blue epoxy paint. 

The customer can specify custom Epoxy paint colours. This needs to be supplied in the form of a RAL code at the point of order. If you wish to enquire about custom paint colours for your motor, please contact us.


IEC Framed Motors

Most modern 3 phase motors conform to the universally accepted IEC frame sizing standards. There are a few caveats; on occasions, OEM's will specify that the motor fits their specific requirements, in which case the motor's external dimensions may differ from IEC standards, or the shaft diameter or length may be different. This is not an issue as we can have the motor disassembled and machined to suit custom shaft requirements.


The IEC Motors standard uses a frame sizing system. Every size within this system is universally adhered to, meaning you can be sure of motor compatibility when replacing an existing motor with a different brand.

Please see the dimensional chart below for a full breakdown of the most common frame sizes and their associated dimensions.

IEC Motor Frame Sizes Chart

NEMA Framed Motors

NEMA (National Electrical Manufacturers Association) frame sizing is an alternative and less widespread motor sizing standard. This standard refers ONLY to the motor's mounting and does not have any direct bearing on the body dimensions. 

We can supply NEMA framed motors. We would require full dimensional details from you as the customer in order to quote. If you require a NEMA framed motor, please contact us.


Motor Efficiency - Ratings IE1 | IE2 | IE3 | IE4 

All modern 3 Phase motors are rated with an efficiency classification band. This is an internationally recognised standard (60034-30-1) and is broken into four categories as listed in the heading, IE1, IE2, IE3, and IE4.

As a basic guide, the higher the number, the higher the motor's efficiency meaning reduced operating costs over the motor's life.


These classifications are also commonly named:

IE1 - Standard Efficiency Motors

IE2 - High Efficiency Motors

IE3 - Premium Efficiency Motors

IE4 - Super Premium Efficiency Motors


IE1 Motors (Standard Efficiency Motors)

The IE1 motors lie in the IE1 class of the international efficiency standard. The output of the IE1 motors is 0.75kW to 355kW. The poles for the IE1 motors are 2, 4, 6, 8, 10 and 12. The speed range of the IE1 motors is from 500rpm to 3600rpm. The rpm frequency for IE1 motors is 50Hz or 60Hz. The aluminium frame size for IE1 motors are 56-200. The cast iron frame size for IE1 motors is 80-400. The temperature class for IE1 motors is B class. The cooling technology for the IE1 motors is IC411. The insulation class is class F. The duty type of the motors is Type S. The protection technology used in IE1 motors is IP55, IP56, IP65, IP66. The international standards for IE1 motors include IEC 60034-30 and IEC 60034-2-1.

IE2 Motors (High Efficiency)

The IE2 motors lie in the IE2 class of the international efficiency standard. The output of the IE2 motors is 0.75kW to 355kW. The poles for the IE2 motors are 2, 4, 6. The speed range of the IE2 motors is from 1000rpm to 3600rpm. The rpm frequency for IE2 motors is 50Hz or 60Hz. The aluminium frame size for IE2 motors is 80-160. The cast iron frame size for IE2 motors is 80-400. The temperature class for IE2 motors is B class. The cooling technology for the IE2 motors is IC411. The insulation class is class F. The duty type of the motors is Type S. The protection technology used in IE2 motors is IP55, IP56, IP65, IP66. The international standards for IE2 motors include IEC 60034-30 and IEC 60034-2-1.

IE3 Motors (Premium Efficiency)

The IE3 motors lie in the IE3 class of the international efficiency standard. The output of the IE3 motors is 0.75kW to 355kW. The poles for the IE3 motors are 2, 4, 6, 8. The speed range of the IE3 motors is from 750rpm to 3600rpm. The rpm frequency for IE3 motors is 50Hz or 60Hz. The aluminium frame size for IE3 motors is 80-160. The cast iron frame size for IE3 motors is 80-400. The temperature class for IE3 motors is B class. The cooling technology for the IE3 motors is IC411 and IC416. The insulation class is class F. The duty type of the motors is Type S1, S2, and S3. The protection technology used in IE3 motors is IP55, IP56, IP65, IP66. The international standards for IE3 motors include IEC 60034-1-30.

IE4 Motors (Super Premium Efficiency)

The IE4 motors lie in the IE4 class of the international efficiency standard. The output of the IE4 motors is 2.2kW to 230kW. The poles for the IE4 motors are 2, 4, 6, 8. The speed range of the IE4 motors is from 750rpm to 3600rpm. The rpm frequency for IE4 motors is 50Hz or 60Hz. The aluminium frame size for IE4 motors is 100-160. The cast iron frame size for IE4 motors are 100-315. The temperature class for IE4 motors is B class. The cooling technology for the IE4 motors is IC411 and IC416. The insulation class is class F. The duty type of the motors is Type S1. The protection technology used in IE4 motors is IP55, IP56, IP65. The international standards for IE4 motors include IEC 60034-30-1.