Simulating Soft Starter

[keerth]

Hi,

 

I would like to know how should I decide on the ramp time and the amount of voltage applied (open-loop soft starter)

to simulate a simple soft starter using Matlab?

 

The motor I am using is a 150HP squirrel cage motor.

 

Thank you

 

cheers,

Keerth

[marke]

It depends on the type of soft starter and the starting algorithm used.

first, the initial start voltage must provide enough torque to overcome the load torque at zero speed by a margin to give you an acceleration torque.

Second the voltage profile must enable the voltage to vary at a rate that ensures that there is sufficient torque to accelerate the motor to full speed allowing for changes in load torque as the speed increases.

If you use a simple timed Voltage Ramp algorithm, then you need to ensure that the rate of rise of voltage is appropriate for the inertia of the load. If you have a short ramp with a high inertia load, you will be at full voltage before the motor reaches full speed and have a very high current. If you have a long ramp with a low inertia load, you will have a motor at full speed with low voltage and resultant high slip.

 

Best regards,

Mark.