Diode in series with AC coil

[seanf]

Not much knowledge of electrics or electronics.

A contactor coil for the three phase supply to a large inverter drive for a compressors motor. There's a second inverter driven compressor on this system but it doesn't have a diode? before the 110VAC contactor coil. Anyone familiar with this being done? Thanks.

15329

[Tayters]

A bit of an educated guess here.
N1 on the diagram says 110V so the contactor coil is a 220V one. When it isn't switched the N1 has a path to another phase somewhere. Diode stops the current in this situation.

Cheers,
Andy.

[HVACRsaurus]

Hi,
It’s probably a typographical error
Diodes are generally associated with DC control circuits (not so much AC)
In this instance it would be acting as a half wave rectifier - reasons of practical application are questionable
Cheers

[seanf]

A bit of an educated guess here.
N1 on the diagram says 110V so the contactor coil is a 220V one. When it isn't switched the N1 has a path to another phase somewhere. Diode stops the current in this situation.

Cheers,
Andy.

The other contactors on that system I've looked at before that use the same voltage source are 110VAC coils. Wouldn't the open switch stop the flow anyway? not sure what you mean.

Thanks Andy.

Sean

[seanf]

Hi,
It’s probably a typographical error
Diodes are generally associated with DC control circuits (not so much AC)
In this instance it would be acting as a half wave rectifier - reasons of practical application are questionable
Cheers

Your probably right.
Not sure if its meant to be more that just a diode with it being in a box. Turns out I'm being sent to the site tomorrow so Ill have a wee look.

Thanks HVACRsaurus.

Sean

[seanf]

It was a rectifier and the drawing wasn't quite right. And was told a DC coil had to be used due to the size of the contactor to keep it held in.

[Brian_UK]

Thanks for the update Sean, always good to find an answer.