3 phase induction motor are work under AC supply and this motor is the most commonly use the motor in the electrical industry. There are two types of induction motors available in the industry such as Squirrel Cage Induction Motors and Wound Rotor Induction Motors. We have already discussed so many articles regarding this induction motors. Today we are a plan to discuss the starting methods of these motors.In here we are a plan to discuss several starting methods apply into these types of the induction motor. Following are several starting methods which use to get start this motor.
Starting Methods of Squirrel Cage 3 Phase Induction Motor
When we consider about starting of 3 phase induction motor there are two methods which based on voltage are used.
Following are major two methods which use to starting large three phase squirrel cage motor.
- Reduced voltage starting method
- Full Voltage Starting method
Reduced voltage starting method
The initial current which takes in the tin to the primary side of the three phase induction motor is higher for short period of time. The main reason for this large starting current is due to the lack of back emf into the motor.
When the induction motor is connected to the power supply, at initial stage it takes over five to seven times of full load current. Due to larger starting current, it also produces great voltage drop. So to reduce voltage starting is necessary to start larger three phase motor.
In reduced voltage starting method there are several types and arrangement use for start this motors such as
- By using primary resistor starting method
- Using autotransformer method – At the beginning, the motor feed less voltage and when it start the voltage gradually increase. When it reach out ultimate to its rated voltage. So by using starting current of the motor can control
- Star Delta switch starting methods- This is one of the most popular starting methods of the induction motor.
Full Voltage Starting method
In the full voltage induction, motor starting method the only starting method use is Direct online (DOL) motor starting method.
This is a special motor arrangement method which also equipped with contractors and other motor protection devices.
This is ordinary three phase On/Off Switch which includes over current protection. Direct Online Switch is permitted if the starting current is acceptable to the utility system.
Starting Methods of Wound Rotor Induction Motors
The most famous starting method of wound rotor motor is to add external resistance into rotor circuit.
Squirrel Cage 3 phase induction motor are the most commonly used induction motor type in the industry. Compare to squall cage induction motors wound rotor induction motors are not much popular in the industry.
Hope that now you have some good understanding of how to perform starting of an Induction motor.