Info Require About Selection Of A Soft Starter.

[AB2005]

Dear Mark,

 

I never install anywhere a soft starter; always worked with star delta change-over. Now we are thinking to move to soft starters and replace the old star delta change-overs with soft starters. For this I need your help to select the right device.

 

The motor for which we want to start the installation of SS is a trim waste blower motor 22KW, 40A, 380V, 4Poles. It took almost 12sec to motor to accelerate the blower at full speed. I think a 30KVA SS would be sufficient for this motor. What do you recommend? Any other helpful suggestion?

[marke]

Hello AB2005

 

Any form of reduced voltage starter reduces the torque generated by the motor. The torque reduction is equal to the voltage or current reduction squared.

The motor and load will only start provided that the start current is high enough to spin the load up to full speed.

 

Loads that require a high start torque will require a high start current.

 

Submersible pumps will usually start at 250 - 300% rated current. Fans, crushers conveyors etc may need as much as 450% rated current to develop enough torque to start the machine.

For a high inertia load, use a controlled current soft starter with three phase control.

 

Best regards,

Mark

[AB2005]

For a high inertia load, use a controlled current soft starter with three phase control.

1. Ok. For my application, i need a "controlled current soft starter". Any other more specifications should i care for?
   
2. But it means SS are available in different kind. Please explain if a "controlled voltage SS" is also available in market and where it does use?
   
3. Does SS has built-in overload safety same like inverter drive or we need to install an external OL?
   
4. After a complete start up, does SS by-passes the internal "starting" circuitry and run the motor by other internal "bypass" way?
   

[marke]

Hello AB2005

 

1. The soft starter needs to be rated for the required start current, I would suggest 450% for 30 seconds with a full load cuurnt of at least 22 Amps.

2. Voltage ramp soft starters are the simplest and lowest cost soft starters and are ggenerally good for pumps.

3. Some do and some don't.

4. Some do and some don't.

 

Best regards,

Mark

[AB2005]

Hello AB2005

 

1. The soft starter needs to be rated for the required start current, I would suggest 450% for 30 seconds with a full load cuurnt of at least 22 Amps.

Hello Marke,

The full load name plate current of motor is 40A not 22A.

[marke]

Yes, my mistake.