What is an Electrical Drive?
“Electrical drives” are electrical power systems used to control motion.
For motion control, it involves a complex electronic system or a combination of different systems.
Block Diagram of electrical Drive
Parts of Electrical Drive
Major parts of electrical drives are
- Power Modulator
- Control Unit
- Sensing Unit
Power Modulator
The power modulator converts the motor’s power to meet the motor’s needs. The power modulator will convert DC to AC if the source is DC and the induction motor is used. It also chooses whether the motor should operate in motoring or braking mode. It also controls the output power of the source as well as the power flowing from the source to the motor
Control Unit
The control unit’s main function is to keep the power modulator running at low voltage and power levels. As needed, it also has a power modulator. It also generates commands for the power modulator and motor’s protection. From one input to the control unit, an input command signal adjusts the operating point of the drive.
Sensing Unit
It understands certain drive parameters such as motor current and speed. This is mainly required for protection or closed-loop operation.
Types of Electrical Drive
Electrical drives are classified into various types based on the following parameters. They are
- Based on Power Supply
- Based on the number of motors
- Based on Speed
- Based on Control Parameters
Based on Power Supply
Based on power supply, drives are classified into two. They are
- A.C Motor Drives
- D.C Motor Drives
A.C. Motor Drives
An AC drive is a device that changes the frequency of the power supply to an electric motor, such as a three-phase induction motor, to control its speed.
A.C motor drive is also called variable frequency drive (VFD) or variable speed drive.
DC Motor drives
It is essentially the speed control system of a direct current electric motor that supplies voltage to the motor in order for it to operate at the required speed.
Analog DC drives and digital DC drives are the two types of DC drives.
Based on Number of Motors
Based on the number of motors, electrical drives are classified into three. They are
Individual Motor
Individual motor, will have a separate drive motor for different parts of a machine.
For Example Lathe machine.
Multi-Motor
In Multi motor, special motors are provided to operate the various parts of a machine.
Example: Cranes.
Group Drive
A single shaft connects the motor to other machines, which are connected to the shaft by belts and bolts. In this case, a single motor acts as a power source for two or more machines
Group drive is the cheapest among these.
Based on Speed
There are two types available in this category. They are
Constant Speed drive
More or less constant speed drives, squirrel cage induction motors, and manual controls are used in machine tools.
Variable Speed drive
Variable speed drives are used to control machine speed, acceleration, deceleration, torque, and, finally, machine direction.
It is used to cut down or reduce energy consumption.
Based on Control Parameters
There are three types available in this category. They are
Vector Control Drive
Vector control is more accurate than any other type of variable frequency drive (VFD).
In this control mode, torque and speed are controlled using the pulse width modulation (PWM) techniques in the inverter.
They are used for AC synchronous and induction motors.
Constant Power Drive
A constant power drive at that speed limit is when a motor’s armature carries a rated current and delivers constant power over a specific range of control.
Constant Torque Drive
Constant torque load type drive is characteristic when handling fixed volumes.
Examples: screw compressors, conveyors, and feeders.
Application of Electric Drive
- This drive’s primary application is electric traction, which is the transportation of materials from one location to another.
- It is used in transportation systems, paper machines, textile mills, machine tools, fans, pumps, robots, and washing machines.
Advantages of Electrical Drive
The advantages of electrical drives are
- It has a very large range of torque, speed, and power.
- Their work is independent of the environmental condition.
- Pollution free
- Easy to start and it does not require any refueling.
- High efficiency
Disadvantages
- Higher initial cost
- High maintenance
- High attention required
- The power breakdown totally stops the entire system