VFD is blowing my RCD

[cropwell]

I had a look though the Huanyang inverter manual and the only reference I can find to PWM is SPWM, which is used within the inverter to control output switching. If your arduino is putting out 5v PWM signal and you have connected it to VI it will be switching on and off like it is stupid. What software are you using on the arduino. If you are using GRBL v0.9 then D11 should put out a 0-5v analogue signal
https://github.com/grbl/grbl/wiki/Connecting-Grbl. I have the feeling that describing D11 output as PWM is in error.

[Doddy]

If you are using GRBL v0.9 then D11 should put out a 0-5v analogue signal
https://github.com/grbl/grbl/wiki/Connecting-Grbl. I have the feeling that describing D11 output as PWM is in error.

No. The MEGA328/2560 based arduinos do not have a DAC, or any other form of analogue output. They provide a number of PWM-enabled discrete outputs (those prefixed with a tilde on the board silk-screening) with the signal value switched between GND and VCC - which if used for e.g. LED drives allows a direct control over the LED luminance, similarly for a DC motor drive; but the output remains a digital PWM signal (they do, however, support multiple ADC inputs)

[cropwell]

No. The MEGA328/2560 based arduinos do not have a DAC, or any other form of analogue output. They provide a number of PWM-enabled discrete outputs (those prefixed with a tilde on the board silk-screening) with the signal value switched between GND and VCC - which if used for e.g. LED drives allows a direct control over the LED luminance, similarly for a DC motor drive; but the output remains a digital PWM signal (they do, however, support multiple ADC inputs)

You are right Doddy, I have had a closer look at the AnalogueWrite function. The DAC converters in the arduino put out a variable duty cycle PWM 0-5v. I have a feeling that that is where the OP's problem lies. I fell into the trap of assuming that, when Arduino described the board as having DAC function they meant in in the true sense. Maybe a simple RC integrator would prove the root of the problem, but in the long term an OpAmp circuit would be better (to give a better 0-5v). I am surprised that the inverter does not have an integrator on the input VI.