motors and drives

The 3-phase induction motor is the most widely used source of motive power in industry. Such motors consume about 65% of all energy used in industry and commerce. For any industrial enterprise it is therefore essential that every effort be spent in determining how this consumption can be reduced. Examples of how this can be achieved include reducing the motor speed, the torque and the actual running times all of which will lead to a reduction in the energy used. Small improvements in efficiency will often make economic sense where the equipment is operating for thousands of hours per year.

Organisations can make considerable energy and cost savings by carrying out a programme to examine how their motor systems are used. For each system an organisation should determine:

• Does the motor need to be on? The cheapest way to save money is to switch a motor off when its not needed.
• How can its efficiency be improved? A high efficiency motor can use 3-4% less energy and will rarely cost much more.
• Is it correctly sized for the job? Many motors are too big for their intended purpose. Always buy motors that match the load requirements needed.
• Can its speed be reduced without compromising its purpose? Fitting variable speed drives enables the motor to be driven at different speeds in order to match the load required. Lowering the speed of a motor by 20% can save 50% in the energy a motor uses.
• How can good maintenance practice improve efficiency? A rewound motor will almost certainly be less efficient compared with a new one. The increase running costs will often wipe out any initial saving made.