An auto transformer starter controls the starting current during the starting phase of an induction motor. Industries use this application primarily for high-starting torque-required applications such as compressors, pumps, fans, and more. It mainly reduces the starting power drawn from the auto transformer.
What is an Auto Transformer Starter?
Connect the motor to the single winding of the transformer in an autotransformer starter. The transformer steps down the starting voltage to control the start-up of the motor. This method applied reduced the voltage and current in the motor windings. Compared to other types of starters, the autotransformer starter is highly efficient. It draws less power during the startup process of the motor.
An auto transformer consists of single-core copper wire wound around the laminated magnetic core. The transformer coil has three taps.Connect the motor to the middle taps and the supply voltage to the outer taps. Connect the motor to the same windings as the supply voltage.
Auto Transformer Starter
During the start-up process. Connect the supply voltage to the middle taps and apply reduced voltage to the outer taps of the windings. This will result in reduced voltage being applied to the motor windings.
Working of the Auto Transformer?
The autotransformer starter, It uses an autotransformer reduced control voltage applied to the motor during the starting process of the induction motor. During the start-up process, the contactor contact closed. The autotransformer has several taps that allow for voltage reduction in several stages. The reduced voltage is applied to the motor during the starting process. The auto transformer reduces the inrush current and starting torque of the motor. which helps to prevent damage from any such type of electrical threats.
Once the motor reached its full operating speed, The autotransformer bypass and directly connect the motor to the power supply sources.Connect overload devices to provide protection from overload, overheating, and other types of heating. This highly efficient and recommended type of induction motor starter is called a soft starter.
To construct an autotransformer, wind a single copper wire around the magnetic core to create multiple taps for applying different voltage ratings. Auto transformers have a construction similar to that of conventional transformers, with the only difference being that they interconnect the primary and secondary windings.
Wind insulated copper wire around a magnetic core made of iron or steel to create the windings for an autotransformer. This design helps in reducing the many types of electrical energy losses like hysteresis loss and eddy current loss.
The auto transformer windings connected into the two parts are: Primary windings and secondary windings
- Primary windings are connected to the input power supply.
- Secondary windings are directly connected with the load.
The taps on the windings are used to vary the voltage applied to the load. I have also a step-down and step-up concepts similar to the conventional transformer.
The mathematical equation of the auto transformer starter
To find the starting voltage find out applied by the auto transformer starter during the starting process
The equation is given by:-
V2 = V1 × (T2 / (T1 + T2))
- V1 = is the supply voltage.
- V2 = the voltage applied to the motor.
- T1 = is the number of the windings in the primary windings.
- T2 = is the number of the windings in the secondary windings.
For more information about transformer Core type transformer
Application of the auto transformer:-
- Air compressor:-Use an autotransformer to control the speed and airflow of the compressor as per industrial requirements
- Pumps:- The auto transformer is the main role of managing and controlling the speed of the pumps to manage the flow of fluids used in irrigation pumps, industrial ventilation, and other equipment.
- Conveyors:- To manage the speed of the moving equipment on the conveyor and for soft starting of the conveyor by just reducing the starting supply to the motor of the conveyor.
- Hoist:-Use machinery equipment and electrical motors to lift, handle, or lower heavy-weight equipment.For soft starting of the motor by auto transformer to can manage the load of the machinery.
Frequently asked questions
1)What is an auto transformer?
Wrap a single winding around the metal core to create a laminated core type.To increase or decrease the load on the motor
2) What are the advantages of using an auto transformer starter?
The auto transformer help in reducing the inrush current and starting voltage of the motor. And improved the speed of the motor and increase the efficiency of the motor and protect from the high starting current to the motor windings.
3)How do you apply voltage to the motor using an autotransformer?
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