What is Soft Starter & Advantages of Soft Starter

by

What is Soft Starter & Advantages of Soft Starter

Q. State four advantages of soft starter

  • When starting, AC induction motor develops high torque than its required value at full speed.
  • This mechanical stress is transferred to the mechanical transmission system resulting in excessive wear-tear and premature failure of chains, belts, gears, etc. Additionally, sudden rise in speed also has a large impact on input supply with high inrush currents drawings + 600 % of the normal current.
  • The use of Star Delta can only provide a partial solution to the problem.
  • Soft starter provides a reliable and economical solution to these problems by delivering a controlled release of power to the motor, thereby providing smooth, steepless acceleration and deceleration.
  • Motor life will be extended as damage to windings and bearings is reduced. Soft Start and Soft Stop is built into 3-phase units, providing controlled starting and stopping with a selection of ramp times and current limit settings to suit all applications.
  • Soft starters are essentially stator voltage controllers, helps to overcome above problem. It helps to restrict starting current and also provide smooth start and stop operation.
What is Soft Starter & Advantages of Soft Starter

Application

Number
of working hours

Number
of jobs

Energy
consumed in kWh

Saving
in kWh

Saving
in %

Grinding machine :

 

 

 

 

 

Without soft starter

7

55

168.0

–

–

With soft starter

7

51

136.8

31.2

18.6

Lathe machine ( kW)

 

 

 

 

 

Without soft starter

7

231

96.4

–

–

With soft starter

7

228

76.4

19.6

20.4

Advantages of soft starter : 

1. System efficiency improves.

2. Energy losses in line reduces.

3. Small line voltage drop in operation of motor.

4. Power factor improves.

5. Low starting torque.

6. Motor is protected from mechanical stresses.

7. Smooth starting operation.

8. M.D. is controlled as current is limited.

9. Less mechanical maintenance.

10. Saving in operating cost.

Working of soft starter : This delivers a controlled power to the motor. This provides stepless/ smooth acceleration/ deacceleration.

Construction : It consists of thyristor in main circuit.

  • The motor voltage is regulated with a printed circuit board.
  • So, as the voltage is low at the time of starting the current and torque is lower.
  • At start it provides low voltage to motor. 
  • This enables to adjust the play between the gear wheels or stretching driving belts or chains etc. 
  • In other words, it eliminates unnecessary jurks during start.
  • Gradually, the voltage and the torque increases so that the machine starts to accelerate.
  • The line voltage drops, so the losses at start are very low.
  • It provides a reliable and economical solution to overcome problems related with starting.

Leave a Comment