How to choose an electric motor?

How to choose an electric motor?

Many electric motors exist for manufacturing machines. They equip all types of industrial and agricultural applications and are offered with many different characteristics. We explain how to choose an electric motor.

Choose a three-phase motor or a single-phase motor?

First, it is necessary to know the supply voltage of your electric motor. There are single-phase voltage and three-phase voltage.

Single-phase voltage is mainly used for electric motors that will be used for low-power applications. The 220v electric motor is available from 0.12 to 3kw so it can only equip domestic applications or low-power machine tools. 220v electric motors generally equip compressors, fans, mechanical reducers or machine tools (band saws, lathes, milling machines, drill presses…). They can be equipped with a single capacitor or two capacitors.

220v electric motors equipped with a single capacitor are used for applications without a need for starting torque (fans or mechanical reducers) however 220v electric motors equipped with two capacitors are to be used for applications with a need for starting torque (compressors, concrete mixers, woodworking machines, car lifts). They have the same dimensions as three-phase motors.

Three-phase motors are used for industrial and agricultural applications of all types. They are available from 0.06 to 1000 Kw in low voltage.

They can therefore equip applications requiring significant torque such as pumps, compressors, mechanical reducers, fans and all other industrial or agricultural applications. They must be supplied with a three-phase voltage of 230 or 400V.

The higher your supply voltage, the lower the current consumed by your three-phase motor will be. Moreover, it is important to select a high-efficiency motor to reduce the absorbed power of your three-phase motor.

How to select the right characteristics for your electric motor?

As we have just seen, it is first important to know your supply voltage. However, many other characteristics are important to know how to choose an electric motor.

First, select the power of your asynchronous motor. This information is indicated on the nameplate. It is generally indicated in Kw.

You must now select the rotation speed. Electric motors are generally offered at 50Hz at 3000rpm, 1500rpm, 1000rpm or 750rpm. As a reminder:

• 3000 rpm electric motor = 2 Poles
• 1500 rpm electric motor = 4 Poles
• 1000 rpm electric motor = 6 Poles
• 750 rpm electric motor = 8 Poles

The rotation speed will determine the size of your electric motor; the lower the rotation speed, the larger the size of your three-phase asynchronous motor will be.

It is now time to select the type of mounting for your electric motor. Each asynchronous motor is offered in 5 different mounting types:

Foot mounting B3 (IM1001 – IM 1011 – IM 1031 – IM 1051 – IM 1061 – IM 1071)

Foot and flange with plain holes B35 (IM2001 – IM 2011 – IM 2031 – IM 2051 – IM 2061 – IM 2071)

Foot and flange with tapped holes B34 (IM 2101 – IM 2111 – IM 2131 – IM 2151 – IM 2161 – IM 2171)

Flange mounting B5 (IM 3001 – IM 3011 – IM 3031)

Flange mounting B14 (IM 3601 – IM 3611 – IM 3631)

This characteristic is essential because the mounting can be different for each application.

To conclude the essential characteristics for knowing how to choose an electric motor, for replacing an electric motor, you will need to know the shaft height of your three-phase asynchronous motor.

The shaft height (type) determines several factors. This shaft height can be standardized or reduced. It determines the diameter and length of the shaft, the measurement of the wheelbase of the mounting feet or the outer diameter of the flange.

It ranges from size 56 to size 630. This shaft height complies with standard EN60034-7.

Each three-phase motor can be equipped with a brake, roller bearings (from size 180), a specific protection rating or even an insulated bearing.

Do not hesitate to contact us to find out how to choose an electric motor.