10-18-2010, 07:06 PM
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 | | | Join Date: Feb 2007 Location: USA
Posts: 401
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I have been building a custom machine for someone that uses G540 and a small VFD to control a three phase spindle motor. I set up the pulleys, PWM spindle outputs, etc in Mach but kept having the curious problem of the motors speed reducing when I asked for a speed from about 65% of the max spindle speed. There was a brief acceleration but then it slowed down.
After confirming that Mach was doing as it should I hooked up the o-scope to the analog input of the VFD and saw a bunch of noise on the analog input line. When ever the motor was running it was creating enough noise on the analog input to mess things up.
The solution was quite easy though. Since I have the VFD outputs brought out to a DB9 on my control boxes I was able to solder a 0.001 uF ceramic cap across the DC Common and VFD out from the G540. This cleaned up the signal and now the G540 and VFD are playing quite happily together.
I just thought I would drop a quick note here to perhaps save someone else a bit of head-scratching later.
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Jeff Birt |
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