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Centrifugal Compressor


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Dear All,


I need some urgent help for selecting Softstarter for Centrifugal compressor application. Im attaching the load torque curve of the compressor. http://rapidshare.com/files/181073531/win6...Curve_50_Hz.pdf. Starting time required for the compressor is 5-12 seconds.


Motor details are AMbient temp = 45 deg c

Motor rating = 410 KW

Operating volt = 415 +/- 10%, 3 ph, 50 Hz +/- 3%

Full load current = 650 A


I have selected Emotron Softstarter of 500kw rating, 710A current with 300% overload for 30 sec. Will this be suitable for this compressor? How do we determine from the load torque curve of compressor, that it can be started with a softstarter? Presently he is using FCMA type starter and want to switch to SCR soft starter.




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Hello Anurag


First, yes you can use a soft starter to start this compressor, but the start current is a function of the speed/torque curve of the compressor and the speed/torque and speed/current curves of the motor.


There are major variations between the start characteristics of motors and the start current variation for a given load can vary by more that 50% depending on the motor.


Do you have any data on the motor? I would need this to comment. Without this data, I would allow for a start current of 400 - 450% from my experience.


Best regards,


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