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PWM frequency for L90 valve

ramasubramaniansathishr 1 month ago • updated 1 month ago 4

Hello sir,

I am working with a Parker L 90 valve. The recommended PWM frequency is 100 to 125 hz. I wanted to understand the reason behind.Does this has anything to do with the Resistance/inductance of the coil ? Like the rise time of current in coil ?

If I run the coil with high PWM frequency say 2000 hz , will the current ever reach to maximum (I = V/R) ?

Is the recommendation of 100 hz only for avoiding switching losses or it has to do with performance as well .

Thanks

Sathish.R

To achieve repeatability in actual spool position a lower PWM frequency is required (100 - 125 Hz). This provides an oscillation of the spool to overcome hysteresis. In some cases a slightly higher frequency may be used if a vibration or oscillation in the consumer can be detected but in my experience never more than 140 Hz.

Hi sir ,

Thanks for reply.

I agree that dither frequency and amplitude has to be set such that the hysteresis is overcomed  .

Some websites ( link below) claim that high frequency PWM is better and dither can be added to it separately with required frequency and amplitude

I had some questions because of that.

So what difference will be there between PWM and dither ? Except that we vary the current by varying the width of pulses of PWM.

Best regards




http://www.axiomatic.com/pulse-width-modulation.pdf







Hello.


In other systems you can maybe set the PWM frequency and dither frequency separately.

You would add a small oscillation (the dither) on top of the PWM to avoid stiction and hysteresis.

In an IQAN system the PWM frequency is low enough that it creates an oscillation by itself, thus the PWM frequency is also the dither frequency.