Electrical drive

Electric drive:

    The motion of electrical machine is controlled by some systems, this type of systems is called as an electrical drive. A Drive is a combination of various systems combined together for the purpose of motion control. Electric motor is used to control the system and that’s why this drives in known as electrical drive. It used prime movers. This prime mover supplies the mechanical energy to the drive and this this mechanical energy is used for motion control. Instead of prime mover, we can use diesel and petrol engines, hydraulic motor, steam engine, gas turbine and steam turbine as a primary source of energy.

Parts of Electrical Drive

     The main parts of the electrical drives are power modulator, motor, controlling unit and sensing units.

Power Modulator: It used to regulates the output power of the source. It controls the power from the source to the motor. This control of power is done in such a way that motor transmits the speed-torque characteristic as per required the load. The excessive current drawn from the source during the transient operations like starting, braking and speed reversing. This excessive current drawn from the source may overload it or may cause a voltage drop. Hence It restricts the source and motor current. It converts the energy according to the requirement of the motor e.g. if the source is DC and an induction motor is used then power modulator convert DC into AC. It also selects the mode of operation of the motor, i.e., motoring or braking.

Sensing Unit: It senses the certain drive parameter like motor current and speed. It mainly required either for protection or for closed loop operation.

Control Unit: The control unit controls the power modulator which operates at small voltage and power levels. The control unit also operates the power modulator as desired. It also generates the commands for the protection of power modulator and motor. An input command signal which adjusts the operating point of the drive, from an input to the control unit.

Classification of Electrical Drives:

Electrical drives are classified as

         1)      Group drive

         2)      Individual Drive

         3)      Multi motor drive

In addition to these drives are further classified,

         Based on supply:

1)      AC drives

2)      DC drives

         Based on running speed:

 1)      Constant speed drive or single speed Drives

 2)       Variable speed drives

         Based on number of motors:

1)      Single motor drives

2)      Multi motor drives

         Based on control Parameter:

1)      Constant torque drives

                      2)      Constant power drives