Pulsed DC operation of an AC rated Solenoid

[hydro9]

Does anyone have experience of operating a Solenoid designed for 110v AC use with Half wave rectified 220v supply. Alternatively I could possibly design around fullwave rectification and change solenoid coil for 220v AC rating. My assumtion is that either design would work based on equivalent RMS energy levels.
The reason for all this is that I need to control the solenoid by a thyristor.
Maybe I forgetting something, but then my degree is 30years old now. Would welcome any thoughts.

 

[DougMSOE]

My degree is 30+.
Yes it will work and in some areas is quite common.
A little trial and error will knock the rust off.
Just keep the ampere*turns the same and you will be OK.
Also you may have to be careful of the actuation time. With some solinoids the armature may have more inertia than others.
Good luck.

 

[hydro9]

Thanks for that input. You have reminded me of the crucial point. "Got to keep the ampere * turns the same". I must not saturate the core. My plan of sending 220 half sine would potentailly fail because I'll be doubling the peak design current of the 110 volt solenoid even though the RMS current will be the same averaged over a whole cycle.

 

[systmac]

Keeping the ampere turns the same as the AC operating current may not allow the solenoid to pull in. A magnetic structure will require roughly 4 times the current to pull in than to hold.(e.g. horseshoe magnet and metal bar)

To a great extent this is automatically achieved in the AC solenoid because the inductance increases when the armature pulls in completing the magnetic circuit. This additional inductance lowers the holding current so the solenoid runs cooler.

In many larger DC solenoids (e.g. aircraft power relays) there are two coils, one to pull in and a smaller one hold.

Typically 120 VAC coils will operate on 28VDC - but watch the coil temperature during continuous operation. A resistor in conjunction with normally closed contacts may be used to set the coil holding current after pull-in.

My degree is 30+ years of experience.

 

[jbartos]

Suggestion: The RMS value needs to be monitored or calculated:
1. Half-wave Rectifier RMS = 0.5 x Amplitude
2. Full-wave Rectifier RMS = 0.707 x Amplitude = (1/sqrt2) x Amplitude
3. SCRs can create a portion of a half of the sinusoid, i.e.
RMS = Amplitude x sqrt((2 x theta + sin(2 x theta))/(4 x pi))
where
2 x theta = 2 x pi / T1
T1 = bigger part of symmetrically chopped a half of the sinusoid width