design an RC snubber for ac solenoid lock ( inductive load)

Thread Starter

Marcodavid

Joined Aug 1, 2022
39
I am designning ac solenoid lock, read the inductive load needs snubber circuit to protect from inductive turnoff transients

Here is my design

Resistance 8 ohm
Main outlet power source 220 - 50 hz
Inductance 150 mh
Impedance 47 ohm
I (rms) ~ 5A


So do i really snubber circuit? If so iam willing to use rc snubber circuit how to design it?
 

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MisterBill2

Joined Jan 23, 2018
12,690
That is certainly a high power solenoid, (5A x 220V =1100Watts), and as a result the snubber components will be hit with quite a larger transient. In addition, the snubber across the solenoid will have a bit of power dissipation while the solenoid is powered. That does not help much with the part values, but it will affect the power ratings and thus their size.

I offer a suggestion that because of the high power in a fairly small solenoid, that you consider a means of limiting the on time to a very short interval because it will heat very rapidly. It is very much a momentary action device.
 

MisterBill2

Joined Jan 23, 2018
12,690
That is a really large solenoid for a lock?
What is the end purpose of operation.
Certainly Max is correct! The powered door release mechanisms I have dealt with were powered bt 24 volts, and the solenoids did not draw even one amp. Or is this device intending to withdraw a locking bolt in a bolt type of lock arrangement.
Consider that 1100 watts equates to almost 1.5 horsepower, which is quite a lot of power. Heating will be a problem, most likely.
In addition, depending on the location of the lock mechanism, providing adequate protection for 220 volt power will be a big challenge.
 

MaxHeadRoom

Joined Jul 18, 2013
25,626
Although generally Lock/unlock mechanisms are a short one shot operation, not like a regular solenoid that may be retained.
This May be the case here?
 

MisterBill2

Joined Jan 23, 2018
12,690
A coil of wire able to carry five amps with a resistance of 8 ohms will have a lot of wire and a fair size.
so I am hoping for some description of the lock assembly.
One caution is that most high power solenoids are not rated for continuous operation.
 

Thread Starter

Marcodavid

Joined Aug 1, 2022
39
the purpose of using all this large and powerful solenoid is i am making something like a "kick" solenoid need it to move strongly and kick things

Not simple lock

This solenoid will not operating lot of time and will turn on for 1 or 2 sec then turn off, so i think the heat generation will not be that massive

The awg wire used is 18 awg (max current is 2.3A), but as i said this will not operating for so long time.
 

MaxHeadRoom

Joined Jul 18, 2013
25,626
So as I suggested, it is better as one shot which in that case should be OK, You can also build heat sink into the form if needed.
 

Thread Starter

Marcodavid

Joined Aug 1, 2022
39
So as I suggested, it is better as one shot which in that case should be OK, You can also build heat sink into the form if needed.

Yes, i will thing of using heat sink if needed
You can see here in this video an electronic seem to be what i want to do but unfortunately there is no info about the coil or wire

And he is not using snubber circuit! And it is look just fine, i really doubt he did not even calculate the circuit!!
 

Thread Starter

Marcodavid

Joined Aug 1, 2022
39
IOW, until the solenoid (steel rod) has fully entered the coil, up until then, the current will be the resistance of the wire.

If no other electronics, you may get away without a snubber.
Although better placed across the switch.
Oh ok i got it, but i am not willing allow the rod steel to be completely shifted in the coil as in video the rod will not be completely shifted in the coil, it is about half of rod is still out of coil when operated ( is not this true or i am missing this and the rod is completely inside the coil?)
 

MaxHeadRoom

Joined Jul 18, 2013
25,626
The less steel in the coil the higher will be the current, it may be better to use DC, although the initial pull in force will be lower than using AC.
But if you are using a very low operation time, you may get away with it. (AC).
 

MisterBill2

Joined Jan 23, 2018
12,690
Understand that the solenoid design in the photo is the least efficient of all possible arrangements for a solenoid. Do yourself a very big favor and look at some texts on solenoid designs, and look at the GRAINGER on line catalog to see how effective solenoids are made. Almost all of the possible configurations are more efficient that the design shown. Better efficiency means less heating and less current drawn for the same force. Greater efficiency also means you can get the same, or more, force in a smaller package,with less heat.
 

Thread Starter

Marcodavid

Joined Aug 1, 2022
39
Understand that the solenoid design in the photo is the least efficient of all possible arrangements for a solenoid. Do yourself a very big favor and look at some texts on solenoid designs, and look at the GRAINGER on line catalog to see how effective solenoids are made. Almost all of the possible configurations are more efficient that the design shown. Better efficiency means less heating and less current drawn for the same force. Greater efficiency also means you can get the same, or more, force in a smaller package,with less heat.
Thanks for your advice i really appreciate it

But that is what i need in my project, i do not want a very high tech solenoid coil which means more components - more tech problems - more manufacturing cost.
Simple = less manufacturing cost = less tech matter problem = easy production

And for some manufacturing reasons this design is the best

Example
I know i can use DC at 24v to get the 5A and will be same force and same result
But i do not have a good space in my project to add a 24v DC power supply or battery

And the problem like heating and so is not important and can be treated with simple components such heat sink and so on.
 

MaxHeadRoom

Joined Jul 18, 2013
25,626
24v DC at 5a is not equivalent to your first post specifications..
Also AC magnetic devices such as this also require the addition of a shading ring.
 

MisterBill2

Joined Jan 23, 2018
12,690
A more efficient and effective design is not that much more complex, although it does include a few more pieces. So I am NOT suggesting more advanced technology, merely applying what has been known for well over 50 years.Simply adding a bit more iron to coplete the magnetic circuit wil greatly improve the efficiency.
 
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