Thread: Solid state relay for ON/OFF VFD
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07-09-2017 #1
Hi guys,
I am thinking of using this solid state relay to control the motor ON/OFF signal of the Chinese VFD. Also maybe to control the Enable on each of the servos.
RS part 720-3956
I use 24Vdc for the control side, and I've tried this SSR with a simple LED and it switches on/off fine.
My question is: this SSR is rated at a maximum 100mA for the load side and I have no idea what the load would be on the ON/OFF contacts of the VDF or for that matter the servo Enable, I suspect very low. Do you think this would work?
Consequently I suppose these signal contacts would be isolated from any VDF/driver return surge on disconnect and a diode on the load side may not be necessary?
Thanks for your advice.
Edward
Last edited by Edward; 07-09-2017 at 09:31 PM.
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07-09-2017 #2
It's overkill but should work, the VFD should provide it's own trigger voltage and with that all you really need is some basic support components and a suitable transistor.
The maths and technology is very simple and the parts would probably cost pennies online, or less than a fiver from Maplin.
- NickYou think that's too expensive? You're not a Model Engineer are you? :D
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07-09-2017 #3
Thanks Nick,
This relay is quite cheap, around £6 and would just be connected straight to one of the opto outputs of my controller (they can drive up to 80V). I only chose it because it goes with my 24V limits circuit.
Edward
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07-09-2017 #4
If you have a common zero voltage reference it will work.
You think that's too expensive? You're not a Model Engineer are you? :D
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