# The optimal PWM frequency of this proportional solenoid

I have to PWM control this proportional solenoid particularly "GP8 036 A59/150" that works on 12V. I tried from 200Hz to 20kHz - it seems that it accepts any PWM frequency with no overheat or any measurable side effects!
So I chose a frequency out of the natural frequency of the controlled system. The only datasheet I found only mentions the relational duty cycle "ED" rating 100% with no mention to the recommended PWM frequency range as the other similar products.

Does it mean that it shouldn't be PWM controlled?
Has anybody worked with this or similar product and knows the optimal way to control it?

EDIT: The datasheet mention only the 24V versions, this is the part I've

• This page offers some information for you. I used a good search engine with "pwm solenoid frequency"
– Uwe
Dec 30, 2021 at 17:37
• @Uwe Yes, thanks for the page, I reviewed that page & similar before, so I ask about the optimal PWM frequency for this specific solenoid. Dec 30, 2021 at 18:15
• What about looking for a solenoid with similar size and using the frequency useful for that?
– Uwe
Dec 30, 2021 at 20:44
• How about contacting the manufacturer? That’s what I would do first. Sep 8, 2023 at 14:09

Such Solenoids are designed to operate from a 24Vdc supply with a relay/contactor doing the enable/disable

This can be seen from the nominal data (recommended)

100% duty, ie DC. Likewise if you look at the nominal resistance for each variant and the associated nominal current

PArt R A 24V/R
GP8 025 27 0.61 0.88
GP8 036 25 0.7 0.96
GP8 045 22 0.83 1.09
GP8 060 17 1.1 1.4

If you factor in a bit of contactor resistance, they align.

That doesn't mean you cannot PWM this coil

--EDIT-- These proportional solenoids are designed to provide an almost linear relationship between current and force and as such their usage is considering varied current.

How can the current be varied?

1. Linear output stage (ClassA). Viable but extremely lossy
2. PWM. Duty ~ voltage ~ current

But what is the optimal switching frequency? There isn't enough data from the part provided or from other constraints. With increase switching frequency there is a reduction in ripple current which will improve the peak-peak of the current waveform. However, with an increase switching frequency comes increase losses from the PWM stage and also the solenoid's core. At some point there is no net benefit in increasing the switching frequency anymore ( Selection of PWM switching frequency in BLDC motor) as there is no more system benefit while the disadvantages (losses, timing) become tighter and tighter.

There is one other consideration... the core of the solenoid. It does not say whether it is solid or laminated. If it is solid (typical for DC-fed solenoids as it is cheaper) then PWM'ing the coil will cause you more problems as the eddy currents due to the MMF of the applied PWM voltage will result in a massive reduction in terminal inductance ( at least 1/100th ) and thus your ripple current will actually become worse.

How to choose? define your constraints

1. losses
2. noise (electrical and audible)
3. force ripple
4. circuit complexity

from these you can hone in on the "optimal" switching frequency. If such constraints cannot be derived, try 10kHz... if aspects are not ideal try 20kHz, if they get worse, try 5kHz. TYPICALLY it is easier to derived the frequency from conceptualise the constraints but if such constraints cannot be derived then empirical testing to determine if it is "good enough" is acceptable for some industries

• Yes, the datasheet only mention the 24V parts, mine is 12V, I edited the post with its picture.. I wish to know the optimal PWM frequency to optimally derive it. Dec 30, 2021 at 18:21
• I think the optimal PWM frequency does not depend on 24 or 12 V but on the mechanical properties of the solenoid determing the timing of open and close movement.
– Uwe
Dec 30, 2021 at 20:49
• Exactly. It's a function of induction and whether the core is laminated or not - most DC fed are not laminated ....
– user16222
Dec 30, 2021 at 23:01
• @JonRB So as far as it's DC rated, So I think the higher the frequency the better the performance as the induction renders higher frequencies to more DC like current .. Am I right ?! Dec 31, 2021 at 8:17
• yes and no, im adding some additional information
– user16222
Dec 31, 2021 at 13:01