Powering solenoids at higher current for small amount of time- smooth using capacitors?

Thread Starter

john smith_1510419217

Joined Nov 11, 2017
10
Hi,

I'm looking to power at most 10 solenoids at higher current and voltage-around 48V, much more than nominal for greater force, for a short period of time (around 1/10 second) and then hold at a much lower current. Most likely not all at the same time anyway.

However, most cheap power supplies can't provide that kind of current (need around 50A- very rough estimate assuming 5A for each solenoid- this is a massive over-estimate and needs testing).

So I was wondering what kind of power supply system would be suitable. Would I be able to smooth the current using capacitors to store the charge and release when the solenoid demand it? Would capacitors be a viable option or is another approach better?

spec of solenoid (nominal):
JF-1040
24VDC
400mA
25N
10mm stroke

Thanks for any help :)
 

MaxHeadRoom

Joined Jul 18, 2013
21,222
Do not use a SMPS, a Linear supply is far more rugged and reliable in this application. Preferably with Toroidal transformer.
They are designed and equipped with a capacitor bank.
Max.
 

philba

Joined Aug 17, 2017
960
If the solenoid current is 0.4A at 24V, then at 48V it would be 0.8A. So your supply would need to provide, at most, 10 x 0.8A = 8A for 1/10 sec. How will you get 48V?
I think this is an import point that needs emphasis - you won't get the solenoid to pull 5A. At least not at 48V. You'd need to supply 300V to get 5A. Not recommended.

Also, you should characterize your system - how many concurrent strikes will you have? You talked earlier about PWM for holding so factor that in. Then you will have your max current. Build in a safety factor (40-50% I'd guess) but I'm pretty sure you are looking at well less than 50A.
 

tcmtech

Joined Nov 4, 2013
2,867
Using a simple charge pump to nearly double your supply voltage in order to charge a larger capacitor that's supplies the initial higher than stock input voltage would work.

Also when over powering solenoids you may need to consider if the solenoid core material is running at or near its normal magnetic saturation limits in its stock configuration being if it is even if you are hitting it with near 4x the input power you may not actually get anywhere near 4x the pulling force produced for it. Big grey area concern there but still one that may show up once you have everything working and it turns out you only got a marginal gain in pulling force for the added work.
 

MaxHeadRoom

Joined Jul 18, 2013
21,222
You could use a 24vac secondary transformer with a bridge rectifier for the steady state supply.
Use a large capacitor on the output to raise it to 33vdc.
Use a relay with a simple time delay method to disconnect caps, you could even use ~1sec.
You are then back to 24vdc.
Max.
 
Top