History of Electrical Drive:
In 1838, the first electrical drive was developed by B.S. Iakobi in Russia. He first tested a DC electric motor which was given supply from a storage battery and he drove a screw propeller on a boat.
But electric drives were not used in the industry as they lack a proper and reliable electrical energy supply.
When a 3 phase induction motor is introduced by M.O.Dolivo-Dobrovolsky then the industrial use of electric drive becomes extensive.
Nowadays, electrical drives are being widely used in the industry.
An electrical drive is defined as the device which is used to control certain parameters of the motor thus converting electrical energy to the mechanical motion by the use of an electric motor.
Hence, electrical drives are used to monitor and control various electrical motor processes.
In this modern era, electrical drives play a very important role in the industrial and automation processes especially where the requirement of the system is the precise speed.
Block Diagram of Electric Drive:
Follow are the main components of an electric drive:
- Electrical Load
- Electrical Motor
- Power Converter or Modulator
- Supply Source
- The Control Unit
- The Sensing Unit
The block diagram of an electrical drive is as follow:
Electrical loads can be conveyors, fans, pumps etc.
Selection of the electrical motor for the load is determined by the load requirements i.e. speed and torque characteristics.
The motor which best suits the requirements of load is selected and used for load drive.
It is used for the regulation of the output power from the source. Actually the speed, torque characteristic of the load is determined and delivered by the power modulator as required.
They provide output which is either AC or DC.
During the transient conditions like starting or braking the motor draws high current from the source. This can cause the voltage drop or the overloading of system.
The power modulator limits and keeps the balance in the motor current and the source.
There are different types of power modulators like the controlled rectifiers, inverters etc.
Most commonly the 3 phase source is used as a supply for the drives. Rarely the single phase supply is used. 3 phase 400 V is used as a supply for LV motors. For high power motors, higher ratings are used as required.
Some of the electrical drives are also powered from batteries.
The Control Unit:
Control Unit is used to control the power modulator by the help of input signals. It operates on low voltage and power.
The Sensing Unit:
The Sensing Unit senses certain parameters of a motor like speed, current etc. It is mainly used in drive for protection and feedback control.
Sensing unit measure the following parameters:
Advantages of Electrical Drive:
- They can operate in harsh environments like radioactive, explosives etc.
- These drives have high efficiency
- Drives offer clean, smooth and simple operation
- The control is easy
- They offer flexibility
- The drives can be controlled remotely
- The cables are used for the transmission of power instead of long shafts
- They have low maintenance costs
- They can be put under operation instantly
- They offer a wide range of torque, speed characteristics
Disadvantages of Electrical Drive:
- In case of any power failure of drives it completely paralyses the system
- Power supplies are required for its operation so there must be power supply present for its operation
- High power drives can be noisy
- The initial cost is very high
- The dynamic response is poor
- The output power of the drive is low
- Conductor leakages and short circuits in drives can be fatal
Applications of Electrical Drive:
Following are some of the applications of the electrical drives are:
- Electric Cars
- Electric Drivetrain
- Electric Traction Systems
- Belt Conveyors
- Cement Mill
- Paper Mill
- Steel Mill etc.