How did I roast this contactor?

M

Mjohnson

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Hi everyone,
I'm working on my control conversion. I have a 24v contactor that was controlling the 240v going to the VFD. I purchased a 5 amp 24v power supply so that it could supply several items on the machine.
I connected the power supply to the contactor and it seemed to pull in just fine. After about 10 minutes it smoked and was ruined.
What did I do wrong?
Thanks!
Mike
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I'm having a hard time reading the tiny text on the front. Is that a 24VAC contactor? If so, connecting it to 24VDC would generate a lot more heat. Also, if it is not new, the coils do go bad from time to time. I'd also check for the output voltage on your supply with a meter to verify.
 
Oh man! Your're right it's 24v AC! I didn't know they used AC in 24V. I assumed it was DC. Crap!
I'll have to find a 24V AC power supply now.
I have a stepper motor coming with a 24V brake. Do you think it is AC too? Also, are 24V air valves AC as well?
 
If I were in your shoes, I'd throw away that contactor and use one rated for 24VDC. That way you only need one supply.

The stepper brake and solenoids are likely 24VDC, but just double check on spec sheet.
 
Mjohnson said:
Oh man! Your're right it's 24v AC! I didn't know they used AC in 24V. I assumed it was DC. Crap!
I'll have to find a 24V AC power supply now.
I have a stepper motor coming with a 24V brake. Do you think it is AC too? Also, are 24V air valves AC as well?
Click to expand...
FWIW, 24 VAC is output from a simple transformer, no power supply necessary.
 
kb58 is totally right 24VAC is super easy to get with a transformer. Only downside is that if you have other 24VDC devices (more common nowadays) in your system, you'll need a power supply. Best to standardize on one logic voltage if you can.
 
You could probably get a 24v dc coil from Siemens and it may be cheaper than getting a different complete contactor.

Ray
 
Thanks for you help guys! I think I will replace it with a contactor with a 110V coil. This way it will power up the VFD at the same time I power up my steppper drives.
 
Most doorbell trnsformers are 24VAC, You really need to check each device to see if it is AC DC or both.
 
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