Anglian Compressors : specialise in air compressors, screw compressors, piston compressors, air treatment products, air dryers and air compressors


Climate Levy	Why Change?	Strategies	Electric Motors	Compressed Air

ELECTRIC MOTORS AND DRIVES

In the UK nearly half of all electricity use is for motive power. In the industrial sector this rises to 65% of electrical energy used in motors.

The majority of motors in use are AC (alternating current) induction motors. These motors are low cost, reliable and they are available in a range of sizes and speeds. AC motors use electricity to generate magnetic fields that turn the motor. Some of the energy is lost within the motor through friction, magnetic losses in the cores, resistive losses in the conductors and stray flux losses. The first two losses (friction and magnetic) are fixed regardless of the load on the motor whilst the last two (resistive and flux) vary with the load. It is for this reason that lightly loaded motors are inefficient.

The cost of an electric motor can be deceptive and in particular the annual energy cost to run the motor can amount to ten times its purchase cost. Therefore ensuring that the motor is correctly selected for its intended purpose is vital.

Many motors are tucked away (including motors used in compressors) in places where they are not seen, they have become an accepted part of the structure and their use in not noticed. Savings can be achieved by asking questions about each motor in use:-

Is the equipment still required?

e.g. use of an area may have changed so that an point-of-use compressor is no longer needed

Can the Compressor be turned off?

e.g. during lunch times or non-productive periods

Is it possible to reduce the load on the motor?

e.g. ensure that the compressor is well maintained

Can the motor losses be reduced?

e.g. avoid oversized compressors and use high efficiency motors (EFF1)

Can the speed of the motor be reduced?

e.g. investigate all opportunities for reducing operating speeds, as this has a big impact on running costs. There is a cube law between the speed of a motor and its power consumption. Hence, if the speed can be halved the power consumption is only one eighth that of full speed. There are a number of ways to change the speed of a motor. Where a fixed speed is required savings may be achieved by:-

Changing the pulley ratio on a belt drive.
Changing to a slower speed motor.
Changing the gearboxratio.

Where multiple speeds are required:-

Install a variable speed drive (VSD) compressor, these units are also optimized to have soft start facilities (which reduces wear and tear on the drive system)

When replacing a compressor always ensure that it is fitted with high efficiency motor (EFF1), these are built to higher tolerances using better materials and are therefore more efficient by 3% or 4%. Often there is only a very small difference in the purchase cost of the EFF1.

Compressed Air....