when energized by 120Vac.

Did you mean 12 VAC? The thread starter said he has a coil that is rated up to 24 volts but he's trying to pull it in with 12 volts DC. I wouldn't want to see someone hit a 24 volt coil with 120 VAC. Lots of light and smoke. Maybe even some frayed nerves.

 

Did you mean 12 VAC? The thread starter said he has a coil that is rated up to 24 volts but he's trying to pull it in with 12 volts DC. I wouldn't want to see someone hit a 24 volt coil with 120 VAC. Lots of light and smoke. Maybe even some frayed nerves.

The way I read it the OP has a 120vac coil he wants to energize with low voltage DC he has tried 12v.
Max.

 

Have you manually operated the contactor then see the minimum DC volts it takes to keep it held with the currently fitted coil?
It it still gets hot with this minimum, DC is a lost cause anyway so get a new coil or a SSR to switch the 120V to the coil.

 

I am working on a project in which I want to use DC to actuate a 120V AC contactor. I found out that I can not go over 24VDC, to avoid overheating the coil. I have a 12VDC power supply, but that fails to activate the coil of the contactor. Based on some threads, I found that a 14VDC can be used to actuate a 120VAC contactor.

@MaxHeadRoom Looks to me like Neil has a contactor that is rated for 120 VAC (the contacts). Personally I don't recall seeing contacts like that not rated below 250 VAC, but I could be wrong. If he's concerned that 24 VDC will overheat the coil, then 120 VAC should blow the coil up. He also said that 14 VDC can be used to actuate the contactor. I just can't see how 14 volts will do anything for a "coil" (not contactor) rated for 120 VAC. Perhaps Neil can clarify these points:

1) What voltage is the coil that actuates the contactor rated for?
2) What voltage are the contacts rated for?

Maybe I've got it all wrong. Wouldn't be the first or last time that's happened.

 

I am working on a project in which I want to use DC to actuate a 120V AC contactor. I found out that I can not go over 24VDC, to avoid overheating the coil. I have a 12VDC power supply, but that fails to activate the coil of the contactor. Based on some threads, I found that a 14VDC can be used to actuate a 120VAC contactor.
I need help in figuring out the Voltage and Amperes of DC that is required to actuate a 120VAC contactor.
the contactor I am using is a 'JARD 17322' 2Pole 120V AC
Any help would be deeply appreciated

Last time I looked at a contactor or relay ratings label; the allowable current was less for DC.

 

Last time I looked at a contactor or relay ratings label; the allowable current was less for DC.

The OP I believe is referring to the coil, not the contacts, also Special Purpose contactors are mainly aimed at switching AC applications only.
Max.

 

The OP I believe is referring to the coil, not the contacts, also Special Purpose contactors are mainly aimed at switching AC applications only.
Max.

Then DC will see the resistance of the winding wire instead of inductive reactance.

An AC solenoid may not have any gap to release residual magnetisation that may occur with DC.

Conversely; a DC solenoid will be like a shorted turn if you feed it AC.

At the end of the day - if DC makes the AC solenoid get hot; put some resistance in series and hope it doesn't forget to unlatch when you turn the current off.

 

At the end of the day - if DC makes the AC solenoid get hot; put some resistance in series and hope it doesn't forget to unlatch when you turn the current off.

Pretty much, However i have never seen one not release. I have observed some that I thought released slower but I never found it worth worrying about in the applications I was doing it with. Last resort to make something work has it compromised.

Now that said, I have made capacitively coupled type DC power conversion circuits to run 12 and 24 VDC coils on 120 and 240 VAC power many times.

In fact pretty much every digital outlet timer uses that method to operate their internal power and relay circuits.

 

Conversely; a DC solenoid will be like a shorted turn if you feed it AC.
.

....Huh ????
The reverse, Maybe.

I thought the discussion was contactor coils?
Max.

 

....Huh ????
The reverse, Maybe.

Max.

Ever wondered why they use laminated cores in transformers?

 

Ever wondered why they use laminated cores in transformers?

Um - yes. Why?

 

Looks like I may have to do another empirical test to disprove another Urban myth, like the one I did for feeding DC relays with rectified AC and 100% ripple!
Suggested that chatter would ensue!
Max.

 

Um - yes. Why?

Elimination of eddy currents.
Max.

 

Looks like I may have to do another empirical test to disprove another Urban myth, like the one I did for feeding DC relays with rectified AC and 100% ripple!
Suggested that chatter would ensue!
Max.

Most wont given that the naturally slow -ish rate of core flux density change tends to give them a magnetic circuit collapse response time that's slower than the DC 50 - 60 or 100- 120 Hz ripple rate is. Some will give off a slight to noticeable hum but I have never seen one outright chatter its contacts from it.

Or at least of all the units I have seen over the years I have never seen a non application specific relay or contactor with a DC coil chatter from line hum on its DC coil.

 

In the test I did, I believe it was reported in this forum, I took several different relays, down through the hysteresis point of both pick up and drop out points and there was zero evidence of any chatter or other adverse effect.
Max.