Home » Case study » One VFD control 3 compressors

One VFD control 3 compressors

Refrigeration compressors, air compressors or gas compressors? Irrespective of which type, the best solution is to have 3 individual variable frequency drive (VFD) running the compressor. These can be started in sequence to minimize power surge. A more economical solution would be to use a single VFD for startup and modulation of a compressor. When this compressor runs to full speed, a bypass contactor kicks in and the VFD can be switched over to a second compressor and then the 3rd when all compressors are running. For added reliability, it may be possible to add a standby VFD. I don't see any advantage of using a single large variable frequency drive for 3 compressors other than the need to synchronize them. Is there such requirement???

I only use 1 VFD to 2 Motors in vibrating feeders, with the thermal protection. The better option is indeed to by 3 VFD, Gozuk is fine, programming them is a drag but they work just fine. Profibus connection is a plus if control is to be made by plc, but depending on what you pretend to do with then... you could just install 3 pressure transmitters in the pipe and adjust their output to the needs of the facility. You need to install output filter in case the cables between the VFD and the motor are longer than 60 / 70 m.

But! here's a question, why don't you just do this:
Keep 2 of them with star/delta
By 1 VFD
Only 2 compressors work at a time, one S/D and one VFD
The S/D keeps full power all the time and the VFD acts like a "jokey pump" that varies the speed as it is needed.

Considering that 2 are enough to satisfy the facility needs.

- - - -> by: VFDs.org

Why do have 3 compressors? I think operational requirement is:

Running ==> 2 Nos.
Standby ==> 1 Nos.

Are these centrifugal compressors or positive displacement ones.

Are these compressor outputs connected to a common header?

Any way best and most efficient way to run compressor is to use individual drives unless by mistake you have bought an oversized power stack.

- - - -> by: Dinesh R

it is better consult the manufacture of compressors before installation of the VFD,they should support or other wise there may be continuous problems of mechanical seals and some parts wear & tear.and then go three individual drive & keep the system healthy.

- - - -> by: Sharad

A well thought out and practical approach to offer the correct solution. I sometimes wonder if engineers are under pressure to save money but lose sight of the longer term implications of machine life and safety. Stop trying to save a couple of bucks and do it right guys. Actually management puts a lot of pressure to save money on every aspect. And in case of utility section they put a lot of pressure. But in long term vision it doesn't save money as later on we have to spend on maintenance. So its better to spend some extra bucks initially.

- - - -> by: Phill