mkgrady
Senior Member
- Location
- Massachusetts
I have a customer that has one feed to a manual transfer switch. The switch feeds two 75 HP compressors but just one at a time. One compressor is the normal and is run with a VFD. The other compressor is the back-up and has just a line voltage starter. Each is a packaged unit with all kinds of internal controls
The customer wants to make the transfer switch automatic. When the pressure drops in the compressed air system, they want the back-up compressor to come on-line and have the normal compressor go off.
Now here is the problem, two suppliers say their suppliera are not interested in making a custom auto transfer switch. Custom because the normal auto-transfer switch switches between sources not loads. Also, the normal auto switching takes place upon a loss or normal power. In my case I want the switch to transfer upon loss of pressure.
Although the components involved would be large because of the motor sizes, the control sequence seems pretty simple. It occurred to me that if the parts are available I could make the auto transfer switch with some very large relays. The voltage is 208-3 phase. The largest total compressor package amps is 228 and it has a 250 amp contactor for the motor. Does somebody make a three pole double throw 250 amp relay? Anybody have any advice on this?
The customer wants to make the transfer switch automatic. When the pressure drops in the compressed air system, they want the back-up compressor to come on-line and have the normal compressor go off.
Now here is the problem, two suppliers say their suppliera are not interested in making a custom auto transfer switch. Custom because the normal auto-transfer switch switches between sources not loads. Also, the normal auto switching takes place upon a loss or normal power. In my case I want the switch to transfer upon loss of pressure.
Although the components involved would be large because of the motor sizes, the control sequence seems pretty simple. It occurred to me that if the parts are available I could make the auto transfer switch with some very large relays. The voltage is 208-3 phase. The largest total compressor package amps is 228 and it has a 250 amp contactor for the motor. Does somebody make a three pole double throw 250 amp relay? Anybody have any advice on this?