Saving money with energy efficient motors

Although upgrading system components requires capital investment, in almost all cases this is paid back in a short space of time as a result of efficiency savings.

You can improve the energy efficiency of your processes by adding variable-speed drives (VSDs), 'soft starters' and 'smart' motors.

Variable speed drives

Where an electric motor serves a variety of load conditions or has a continuously-variable demand, the use of a VSD will improve energy efficiency by optimising motor speed. As well has having the ability to save significant amounts of energy, VSDs also have other benefits, including improved process control and the ability to control more than one motor.

Many VSDs also have a further energy-saving mode that's normally described as an 'energy optimising' feature. This reduces inherent losses and makes further energy savings.

Soft starters

A motor draws a high current when it starts up. To reduce the starting current you can fit a soft starter to your motor. These limit the current to the motor during start-up, to provide a smoother start. As a result, the life of the motor is extended because wear on the mechanical parts is reduced and electrical components are prevented from overheating. Soft starters can also increase the recommended number of 'starts' per hour, which is useful if your motors are subject to frequent stopping and starting.

Smart motors

Smart motors combine the functionality of an electric motor, a VSD and a control unit. They are able to analyse load conditions without having to feed back information to a central control system. This means faster response time and reduced cable losses. All electrical cables have electrical resistance, so a small amount of power is lost in the form of heat between one end of the cable and the other. Using smart motors to improve process automation can save up to 15 per cent of a motor's running costs.

Transmission systems

It's important to match the correct transmission system to your motor. The most commonly used transmission systems are:

• direct drives, where the load is coupled directly to the motor shaft. It is important that the drive is correctly aligned with the motor to prevent energy losses.
• belt-driven pulleys, where the output speed is adjusted by a pulley system of different-sized wheels connected by a belt, and the pump/fan speed can be reduced by changing the pulley ratio.
• gearboxes, where the output speed is adjusted using a series of gears