Why VSD for Compressors

The terms can be interchangeable, though VSD may include some devices other than variable frequency. Usage is somewhat a matter of local custom.

VSD (Variable speed drive) is a broader term used to save energy, reduce mechanical wear and tear, reduce noise level etc.

VSD and VFD could be taken to mean the same thing.

However, if one wants to go a little deeper, engineering wise, then a difference arises.

The AC drive should ideally be refered to as a VFD as it uses change of frequency to vary the speed.

The DC drive should be refered to as a VSD as it achieves speed change by either varying Armature voltage or Field current.

Regards,

George

They use VSD because their concern is the speed of the compressor element which is what they are advertising. VFD (variable frequency Drive) would be meaningless unless it is used to vary the SPEED of the element (generally the screw...).

It seems that some readers do not concentrate on what the OP was asking.

My reply is NOT OFF TOPIC and I don't know who was prompted to give an Off Topic to my answer.

Maybe he should read and reply properly: The OP knows what is a VFD or VSD and what they stand for. He is just asking why this VSD is used instead of VFD when the Compressor maker is actually using a VFD drive to vary the speed of the compressor! Every one is trying to educate the OP on what each abreviation means instead of why the compressor maker uses one abreviation instead of the other!

who ever flaged my answer as off topic please think about it ....

VFD = Variable Frequency Drive, no other relevant definition.

VSD = Variable SPEED Drive; could be VFD, could be DC drive, could be a mechanical variable pitch sheave drive, could be an Eddy Current drive, could be a magnetic drive etc. etc. etc. Anything that varies the speed could be called a VSD.

If you are extolling the virtues of varying the compressor speed as opposed to running continuously and unloading to maintain pressure, then it is not immediately relevant how you vary the speed. At some point after deciding this is the way to go, one should investigate the losses associated with the various methods, but if the context was the initial issue only, I can see that use as valid.

VFD commonly used on AC motor and VSD at DC Motor, but generally both have the same meaning