What is the working principle of auto transformer starter?
Autotransformer Starter Principle To activate the motor, the two switches in the circuit like 1 & 2 are closed. Once the switches are closed then less voltage can be supplied to the motor from the autotransformer. This voltage restricts the input current toward the stationary motor to accelerate.
What is the purpose of a auto transformer starter?
An auto-transformer starter makes it possible to start squirrel-cage induction motors with reduced starting current, as the voltage across the motor is reduced during starting. In contrast to the star-delta connection, only three motor leads and terminals are required.
What is auto transformer method?
In this method, an auto-transformer is placed in series with the motor during staring. The transformer action reduces the voltage applied to the motor terminals. Because of the transformer action, the line current is less than the motor current. Thus, this method gives the highest motor torque per line ampere.
What is the use of auto transformer?
The primary purpose of an autotransformer is to regulate the voltage of transmission lines and can be used to transform voltages. With only one winding, an autotransformer adjusts the voltage automatically according to load.
What are the demerits of auto transformer starter?
Drawbacks/disadvantages Auto transformer starter:
- The circuit is quite complex and involves relatively expensive autotransformer.
- Due to the physical size of the whole device, it might not be possible to add the Korndorfer starter to an existing machine if space is scarce.
- Low power factor.
How many contractors are used in auto transformer starter?
The Star/Delta starter is manufactured from three contactors, a timer and a thermal overload. The contactors are smaller than the single contactor used in a Direct on Line starter as they are controlling winding currents only. The currents through the winding are 1/root 3 (58%) of the current in the line.
Can an autotransformer step-up voltage?
An autotransformer can also be used to step the supply voltage up or down by reversing the connections. If the primary is the total winding and is connected to a supply, and the secondary circuit is connected across only a portion of the winding, then the secondary voltage is “stepped-down” as shown.
How is auto transformer current calculated?
It means actual winding power handling capacity is only 1015 KVA but this autotransformer can handle 5000 KVA means auto transformer can handle 5 times more power and 5 times smaller than a conventional 2 winding transformer. Apparent Current = 1015 Kva/220 = 1015 x 1000/220= 4613.63 A.
What are the advantages of autotransformer?
The Autotransformer have many advantages over conventional double wound transformers. They are generally more efficient for the same VA rating, are smaller in size, and as they require less copper in their construction, their cost is less compared to double wound transformers of the same VA rating.
