Gibbons jargon buster #3: What is torque?

It's time for another special blog clearing up some of the terminology used in our industry, so if you've ever wondered "what is torque?" when it comes to electric motors then read on for an easy-to-understand guide.


It’s time for another special blog clearing up some of the terminology used in our industry. Today we’re asking what torque is, and what it means in terms of electric motors.

What is torque?

Torque can be defined as the turning movement exerted by a force. In the case of electric motors, the turning movement is the shaft’s rotation caused by electro-magnetic force.

How is torque measured?

The metric unit of torque is the newton metre (Nm). In Imperial units it’s pound-feet (lb-ft).

How do you calculate torque?

Torque is calculated by multiplying force by distance to a pivot point, which for us is the axis of an electric motor’s rotating shaft. So:

Force (N) x Distance (m) = Torque (Nm)

If the power and speed of a motor are known then torque can be expressed as:

9550 x kW

                                                                

Speed (rpm)

For example, a 2.2kW motor running at 1500 rpm would produce torque of just over 14 Nm, and the same motor running at 3000 rpm would produce 7 Nm torque.

What kinds of torque are there?

Torque generally falls into three categories:

• Starting (breakaway) torque is what’s required to get the rotor turning from a standstill
• Acceleration torque is lower than starting torque as the motor gets up to speed
• Steady-state (operating) torque is what a load continuously demands.

Hopefully this has cleared up the definition of torque relating to electric motors. If you have any further questions on this or any other topic, give us a call on 01621 868138 or email info@gibbonsgroup.co.uk.