Posted 30 June 2006 - 05:59 AM
My customer has a centrifugal compressor application. Motor connected is 6.6kv, 750kw, 76Amps, 2pole rated. Presently the problem is that customer is not getting required flow for his production. Presently the motor is running DOL at 49.5 Hz. Compressor data sheet shows that compressor can be loaded upto 51.5 Hz to get more flow at same head. Presently compressor efficiency is 65% and motor is getting loaded upto 67-68 Amps only at 49.5Hz.
Customer wants to install VFD and increase the speed of motor and thereby get more flow. Our assumption is that because presently the motor is underfluxed at nominal conditions, we can increase the frequency of motor and still be able to get required torque to run the compressory at higher speed and thereby increase flow.
Any suggestions how best we can do this to not let the motor get saturated and get maximum possible speed. I will appreciate reply to this by all.
Posted 30 June 2006 - 06:14 AM
If it is not directly coupled, changing pulley ratios might provide the result you are looking for at a fraction of the cost associated with purchasing/fitting a variable speed drive.
Posted 30 June 2006 - 03:39 PM
Posted 01 July 2006 - 04:06 AM
Yes the motor is 50Hz rated only and the compressor curve says that it can go upto atleast 51.5Hz equivalent to motor speed. With this increase from 49.5Hz to 51.5Hz we can get around 8% increase in flow as per compressor data sheet. Infact we want to try and go upto 54 Hz if possible with motor and compressor to achieve the best possible.
Also we are not considering at 6.6kv drive for this application considering the cost and hence want to go for High-Low_High solution using transformer.
Posted 01 July 2006 - 08:58 PM
The output trafo could introduce further hazardous overvoltages that will be transferred to motor windings.
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