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This is my first time designing a control panel for a motor and my first time using a commercial VFD so sorry if this seems like a dumb question to people who've done it before.
I want to be able to digitally set the frequency of the motor up to 60 Hz (144rpm, 31.8m/min) of a Mitsubishi FR-E720-S30 VFD (they call them inverters) with a Mitsubishi Q00UCPU. I know it can be done with Modbus (or CC-Link etc.) but I think that requires a comm module.
I thought section 6.6.3 of the Mitsubishi E700 user manual had the answer ("use contact signals to perform continuous variable-speed operation, without using analogue signals") but then it turns out that the frequency is still controlled by the inverter in this case and that the digital input it refers to is simply accelerate (RH) and decelerate (RM) based on time values set in the inverter unit. What I was really hoping for (wishful programmer-thinking actually) was a simple way to send an integer between the two devices but I don't think that's possible without an I/O card like the QJ71MT91, so instead I was thinking of outputting a PWM signal to the VFD. Section 5.2.4 says which pins to use for an analogue voltage input using a potentiometer, I thought maybe using a HF capacitor would smooth the PWM output to an average voltage. Maybe that'd work (probably don't even need the smoothing cap) but that's a lot of conversions (frequency -> PWM signal -> average voltage -> frequency) so there must be a better way of doing it.
In fact, looking back over this I probably should just go with the QJ71MT91 module. Any one agree/disagree? Any other advice you can give me (remember I'm new to this)?
I want to be able to digitally set the frequency of the motor up to 60 Hz (144rpm, 31.8m/min) of a Mitsubishi FR-E720-S30 VFD (they call them inverters) with a Mitsubishi Q00UCPU. I know it can be done with Modbus (or CC-Link etc.) but I think that requires a comm module.
I thought section 6.6.3 of the Mitsubishi E700 user manual had the answer ("use contact signals to perform continuous variable-speed operation, without using analogue signals") but then it turns out that the frequency is still controlled by the inverter in this case and that the digital input it refers to is simply accelerate (RH) and decelerate (RM) based on time values set in the inverter unit. What I was really hoping for (wishful programmer-thinking actually) was a simple way to send an integer between the two devices but I don't think that's possible without an I/O card like the QJ71MT91, so instead I was thinking of outputting a PWM signal to the VFD. Section 5.2.4 says which pins to use for an analogue voltage input using a potentiometer, I thought maybe using a HF capacitor would smooth the PWM output to an average voltage. Maybe that'd work (probably don't even need the smoothing cap) but that's a lot of conversions (frequency -> PWM signal -> average voltage -> frequency) so there must be a better way of doing it.
In fact, looking back over this I probably should just go with the QJ71MT91 module. Any one agree/disagree? Any other advice you can give me (remember I'm new to this)?