24v Solenoid - AC vs DC

[Ben Halicki]

Hi guys,

Sorry if this has been asked thousands of times over, but I haven't been able to find a definitive answer (that I understand!).

I have a programmable logic controller that requires 24V DC. I want it to drive 24VAC solenoids, but I don't really want to have another AC power supply just for the solenoids.

Can someone please explain what the difference between an AC and a DC solenoid is? From what i understand, it is just a coil. If I measure the current draw on 24VAC, it is around 30mA, if I make sure it is drawing no more than 30mA on 24VDC, will it eventually damage the solenoid?

Thanks in advance,

Ben.

 

[Harald Kapp]

An AC coil will probably work on DC, not vice versa. With DC you may have to add a series resistor to limit the current.
When using a DC coil with AC, the magnetization may not be high enough to activate the expected operation (e.g. movin a relay contact). AC coils typically use a shader ring to keeep the magnetic field up during the zero crossing of the AC current.

Here's some interesting material.

 

[Old Steve]

Hi guys,

Sorry if this has been asked thousands of times over, but I haven't been able to find a definitive answer (that I understand!).
I have a programmable logic controller that requires 24V DC. I want it to drive 24VAC solenoids, but I don't really want to have another AC power supply just for the solenoids.
Can someone please explain what the difference between an AC and a DC solenoid is? From what i understand, it is just a coil. If I measure the current draw on 24VAC, it is around 30mA, if I make sure it is drawing no more than 30mA on 24VDC, will it eventually damage the solenoid?
Thanks in advance,
Ben.

Using DC, you'll need a different voltage than when the coil is powered from AC. I didn't know the answer originally, so did a quick Google. (Did you try that before asking?)
See here:-
http://ecmweb.com/content/using-ac-coils-dc-power

And a bit more general info, a comparison, here:-
http://www.ledex.com/solenoid-applications/ac-vs-dc-solenoids.html

These are the full search results:-
https://www.google.com/search?q=difference+between+ac+and+dc+solenoid+coils&ie=utf-8&oe=utf-8

Can't you tap the AC from immediately before the rectifier in your 24VDC power supply, then control a relay using 24VDC to switch the 24VAC to the solenoids?

 

[Old Steve]

An AC coil will probably work on DC, not vice versa. With DC you may have to add a series resistor to limit the current.
When using a DC coil with AC, the magnetization may not be high enough to activate the expected operation (e.g. movin a relay contact). AC coils typically use a shader ring to keeep the magnetic field up during the zero crossing of the AC current.

Here's some interesting material.

Sorry Harald, I was typing at the same time. We linked to the same document, too.
(I removed that one from my post.)

 

[Harald Kapp]

No need to be sorry, Steve. This happens. It's a good sign the answer can't be too absurd

 

[Minder]

If you have a linear type 24vdc supply right now, you could come direct off of the transformer secondary, you just need a blocking rectifier between it and the capacitor.
Or simply a 240v/24v transformer.
The resistance of an AC inductive device is very low, it requires the inductive reactance effect (AC) to limit the current.
What is the nature of the PLC outputs, if relay outputs switching can be AC or DC.
The only advantage to AC solenoids is they energize a little faster than DC, but after that DC are the better choice.
M.

 

[Ben Halicki]

Thanks for the replies and links guys, some very useful information there. I had tried googling, but was lost when the posts started talking about inductance of AC vs DC. Not something I really understand yet. The power supply is a 240VAC to 24VDC switchmode, which makes it difficult to tap into (for me anyway...).