3 phase 480 V VFD Contactor and Bypass A-T-L Contactor Pulling in together
3 phase 480 V VFD Contactor and Bypass A-T-L Contactor Pulling in together
(OP)
Our drive and bypass contactors are electrically interlocked only, without any mechanical ties. While I know you don't want these to close at the same time I am trying to understand the ampitude and waveform of them combined - can you help describe what out come voltage would be.





RE: 3 phase 480 V VFD Contactor and Bypass A-T-L Contactor Pulling in together
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: 3 phase 480 V VFD Contactor and Bypass A-T-L Contactor Pulling in together
Here is a link to a company that manufactures a bypass switch:
http://www.acicontrols.com/catalog/display_results...
RE: 3 phase 480 V VFD Contactor and Bypass A-T-L Contactor Pulling in together
Without knowing the nature of the electrical interlock that's quite a bold statement to make. Mechanical interlocks fail far more frequently than electrical ones, albeit usually in a state where nothing can close. It should be entirely possible to engineer a decent electrical interlock.
RE: 3 phase 480 V VFD Contactor and Bypass A-T-L Contactor Pulling in together
"Will work for (the memory of) salami"
RE: 3 phase 480 V VFD Contactor and Bypass A-T-L Contactor Pulling in together
It's obvious that it's insufficient because it doesn't work! Would you want to try to design a retrofit without having all to the system info? Are you that bold?
That's why I referred him to a company the makes bypasses.
RE: 3 phase 480 V VFD Contactor and Bypass A-T-L Contactor Pulling in together
The OP didn't say that his electrical interlock doesn't work... He's just wondering what the effects would be if it failed.
Best to you,
Goober Dave
Haven't see the forum policies? Do so now: Forum Policies
RE: 3 phase 480 V VFD Contactor and Bypass A-T-L Contactor Pulling in together
Also used in cascaded pump systems where a constant pressure is required and a bank of pumps is run with some of them in base load and one in "topping up mode" running off teh VFD. The drive has a built in PLC and switches between motors to allow equal running hours so the maintenance factors are the same.
RE: 3 phase 480 V VFD Contactor and Bypass A-T-L Contactor Pulling in together
mea culpa
RE: 3 phase 480 V VFD Contactor and Bypass A-T-L Contactor Pulling in together
Odd statement there, not sure where it all comes from. Efficiency, yes, if the motor will be running at full speed you eliminate the losses in the VFD when you switch it over to bypass. But the VFD would be effectively correcting the PF if left in. So if running at full speed in bypass, then one would have to add PFC capacitors and a contactor that only closes when the motor power is bypassed around the VFD. In other words that's not a benefit of having a bypass for a VFD, it's a problem that must be addressed.
"Will work for (the memory of) salami"