How is the motor in a single speed compressor affected by VSD operation?
A motor may run a few degrees Centigrade hotter when fed by a VSD but only at full load. The aim of the compressor controlled by the VSD is to provide fine control over system pressure and so it spends far less time under full load operation than it would do otherwise (part of the reason why the system provides such large savings on energy usage). On the other hand the reduction in shock loading during starting with an inverter actually protects the motor and extends its life. At least one manufacturer EnergAir are aware of use a smaller air end on their VSD compressor compared to the equivalent fixed speed compressor, this cost cutting has resulted in higher motor and rotor speeds and the need for specialist ‘high speed’ bearings and grease. The motor bearings and lubrication on all the compressors that we offer to upgrade (virtually all known brands to date) work well within their design parameters and so the issue does not arise. Q. Does running at lower speeds affect cooling? A goo
