What are the components of an electric motor?
Understanding the components of a motor and how it works can show how energy wastage can occur within a business. The diagram (below) shows the various parts that make up an induction motor, from the conduit box, where the electrical input is applied (either directly from the mains/grid supply or from a VSD), to the output shaft. Simply put, as electrical power is applied, a rotating magnetic field is created around the stator (1). This induces currents and associated magnetic fields in the rotor (2), causing the rotor and shaft (3) to spin. The shaft is mounted on bearings (4) and is able to rotate freely. When a motor is connected directly to an electrical supply it will accelerate to a fixed speed. However, when starting, the motor will draw a very high current as it accelerates. This is called the ‘motor starting current’. The starting current generates significant heat and it is for this reason that motor manufacturers normally state a maximum number of ‘starts’ per hour, as excess heat will considerably increase motor wear and reduce life expectancy. When a motor is connected to a soft starter or to a VSD, this starting current can be limited and a much smoother start can be achieved, resulting in less wear on the motor.