Introduction of Industrial Drives:
Electric drives have inherent advantages over other prime movers. Special motors and control gears have been developed to suit every application. Induction motor is the veritable work horse of industry. Squirrel cage induction motor is used for all constant speed applications because of its low cost., rugged design and simple control gear. Wound rotor induction motor is used where one or more of the following consideration are involved:
(i) High starting torque
(ii) Low starting current
(iii) Speed control over a limited range
Synchronous motor is suitable for all constant speed application. It is generally more economical in rating above 100 kW particularly for slow speed drives because of high power factor, better efficiency and lower cost.
DC motors are invariably used where smooth and precise control over a wide range with or without quick speed reversals is needed. The type of electric drive and control gear for a particular application are determined by the following consideration:
(i) Duty ; whether heavy, medium light,
(ii) Starting torque,
(iii) Limitations on starting current,
(iv) Speed control range and its nature,
(v) Need for automatic control,
(vi) Environmental conditions.
Any production equipment used in a modem industry consists of three components. These are :
1. The prime mover along with its control equipment.
2. The motion transmitting device, and
3. The actual apparatus or equipment (load)
The function of the first two components is to impart motion to the production unit. The prime mover (which is an electric motor), the shaft transmitting motion, and the associated control equipment are together called the 'electric drive. The drive together with the load makes a complete drive system.