Relay/contactor spec for Vdc through with 24vDC coil control.

T

TnDrew

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Systems R&D / Maintenance Manager
Hello, I'm setting up a bank of small 90Vdc powered auger feeders.
I would like to be able to provide two different power supplies to the bank... one for high speed, one for low speed, and be able to switch between those using a single 24Vdc signal from a PLC.
So far I'm hitting a blank on sourcing the relay/contactor to accomplish that.
Any suggestions?
Thank you.

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You want a SPDT (Single Pole Double Throw) relay with a 24VDC coil rated for 10A at 90VDC (anything rated for 90VDC will handle any lower voltage).

The thing is, 10A @90VDC is likely bigger than a relay, so it’s probably going to need to be a contractor. Contactors don’t typically come as “Double Throw”, so what you will look for is a 2 pole contactor with at least 1 NO / 1 NC (Normally Open / Normally Closed) contacts.
 
It would probably be cheaper to switch between two NO contactors than one SPDT contactor.
 
hillbilly1 said:
Probably a power relay would work, but the ones I just looked up are not rated for 90 volt DC.
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Which is why I suggested a sealed contact relay, like those used for a starter in a vehicle.

Updated with a manufacturer
www.rinconpower.com

High Voltage DC Contactors | Rincon Power

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LarryFine said:
It would probably be cheaper to switch between two NO contactors than one SPDT contactor.
Click to expand...

You woukd just have to make sure that at no point in time are both SPST N.O. contactors turned ON. Having a separate 24V control line from the PLC for each of two SPST contactors could be used to prevent such overlap. However. a double throw contactor would be preferable if you could get one.

In addition to the contactors that Jim found, here's another possible candidate:

 
hillbilly1 said:
Probably a power relay would work, but the ones I just looked up are not rated for 90 volt DC.
Click to expand...
Appears to be one of the cheating lying china rating of 80 amps DC .No way such a small relay with small contacts and maybe an equivalent #14 gauge wire from movable contacts. Had a customer call me for 25 amp rated cheating Chinese relays that while he got over the internet for a very low price & and lasted a few weeks. They were marked 25 amps @250 volts AC. Discested one if them. Had 16 gauge wire and contacts smaller then ten amp contacts on ice cube relays.
 
garbo said:
Appears to be one of the cheating lying china rating of 80 amps DC .No way such a small relay with small contacts and maybe an equivalent #14 gauge wire from movable contacts. Had a customer call me for 25 amp rated cheating Chinese relays that while he got over the internet for a very low price & and lasted a few weeks. They were marked 25 amps @250 volts AC. Discested one if them. Had 16 gauge wire and contacts smaller then ten amp contacts on ice cube relays.
Click to expand...
Yeah, I was surprised at the 80 amp rating. The ones I get at Grainger are only rated at 30 amps, and apparently they are going to quit selling them. They had them on clearance for $10 or something the last time I ordered one.
 
Siemens, 32A rated DC contractor, 2-NO 1-NC contacts.

In response to an inquiry on these:

The 2-NO + 1-NC contacts are power rated, not control. This is (was) a widely used configuration in the DC drive industry, it’s available from ABB and I think Schneider /Telemecanique too, but I don’t think they have a version that is as small as this one from Siemens.

The 1 NC contact was used to switch in a set of dynamic braking resistors on DC drives, but the manufactures always just used the same power rating in that NC contact as on the NO contacts. But there is no reason it can’t be used for this.
 
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