What are the types of Motor Starting explain each with a Power and Control Diagram?
What is a Motor Starter?
The Motor Starter is a device used to start and stop the motor to which it is connected.
A DOL (Direct On-Line) starter is normally used to start the motor. But for a heavy motor with more power, other advanced starters like Star-Delta, Soft Starter, and VFD Starter are used.
Advanced starter (like Star-Delta, Soft Starter, and VFD Starter) applies less voltage to reduce the high initial current, this voltage reduction is for a short time. As the motor accelerates to its running speed, full voltage is applied to the motor.
The motor starter provides other functionality also to protect the motor from any other fault like overload, single phasing, under-voltage, voltage unbalance, and stall protection.
There are many types of starters used to start the motor, in this blog, we are going to see some basic motor starters and their conversion into PLC ladder logic.
DOL STARTER
DOL stands for Direct Online Starter, most commonly used in the industry to start the motor.
In this method, full voltage is applied to the motor, but the starting current would be very high (usually 5-8 times more than its rated current). For a low-capacity motor, there is no need to reduce the voltage at the start.
Although, it provides all other functionalities like overloading, single phasing, and low voltage.
To develop the PLC ladder logic of the DOL starter, first, we have to look at the control circuit of this starter.
DOL Starter
Advantages:
- Cost-Effective
- Simple in Construction
Disadvantages:
- Initial high current
- Unable to use Heavy Motors
Ladder Logic of DOL Starter
Forward/Reverse Starter
Forward/Reverse starter is another starter used when we need to change the direction of the motor, through this starter, it is possible to operate the motor in both directions.
Forward/Reverse starter works on the same principle as the DOL starter, but it has additional functionality to change the direction of the motor.
Here you can find the control and power wiring of this starter.
Forward Reverse Starter
Advantages:
- Cost-Effective
- Simple in Construction
- High Starting Torque
Disadvantages:
- Initial high current
- Unable to use on Heavy Motors
Ladder Logic of Forward-Reverse Starter
Star-Delta Starter
Star-Delta starter is used for heavy motor applications like Pump, Blower, Crusher, etc.
Star-Delta starter supplies a low voltage initially at the start, this reduces torque also. This starter uses a timer, contactor, overload, etc.
In this starter, the Star connection is used at the start and the Delta connection is used for a normal run.
Star-Delta Starter
Advantages:
- Low starting current
- Good for long acceleration time
Disadvantages:
- Complex wiring
Ladder Logic of Star-Delta Starter
