crazy loud minilathe VFD (??) whine - HELP!

kb58 said:
Assuming that it's digital, that's unfortunately unlikely. The whole thing gets dicey when messing with a 230v circuit without a schematic, like walking out blindfolded on to thin ice. Unless you can get information from the VFD mfg, it gets dangerous guessing. Either put in a VFD that can be adjusted, get information from the mfg, or just live with it.

For what it's worth, a friend has a $25k CNC mill and the squeal on his drives him nuts.
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WELL you have a to figure out the circuit first obviously ... silly to tamper with what you don't understand ... i popped open the control board on front and the business end at the back and found a couple of trimmer pots ... potential good news
 
oh well ... i guess neither of the trimmers seemed to have any effect ... one controlled the speed and the other who knows what so i didn't mess with it too much
 
The trimpots probably are for speed trim and torque compensation, hard to adjust on the fly without some test equipment
The good news is if it's a brush type motor then you could swap controllers- go back to old fashioned tech like KB or similar- you can find them on Ebay for as low as 50$ sometimes, look for models like KBIC-125
You'd be trading high frequency whine for 60 cycle ac hum
M
 
markba633csi said:
The trimpots probably are for speed trim and torque compensation, hard to adjust on the fly without some test equipment
The good news is if it's a brush type motor then you could swap controllers- go back to old fashioned tech like KB or similar- you can find them on Ebay for as low as 50$ sometimes, look for models like KBIC-125
You'd be trading high frequency whine for 60 cycle ac hum
M
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thanks - well i'm up to my ears in 'test equipment' (oscilloscopes meters power supplies etc) but may opt for an alternative - will look into it thanks - still trying to wrap my head around what specifically is 'oscillating' to make the carrier pitch though ... :p
 
Mr. Science said:
thanks - well i'm up to my ears in 'test equipment' (oscilloscopes meters power supplies etc) but may opt for an alternative - will look into it thanks - still trying to wrap my head around what specifically is 'oscillating' to make the carrier pitch though ... :p
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Just put a scope on the motor leads and you'll see the PWM carrier signal. The actual noise is probably coming directly from the motor, resonance. You might try a 1mF cap across the motor leads and see if that quiets it down a bit, or maybe a ferrite ring or two will help. Maybe whip up a low pass filter, might help.
 
Yes most likely the motor singing or a choke if there is one, or both. I'm sure the mfg. made only a feeble attempt at knocking down the harmonics and overshoot- Power components and ferrites cost money which adds to the sales price
mark
 
yes some sort of blocking filter (cap or coil) was my first idea - but doesnt' the motor need to receive that signal for whatever reason? (minilathe voodoo? doesn't it need the PWM signal?)
 
cleaning up after the manufacturer is sort of half the fun of mini lathes though it would seem ...
i'm pretty stoked ... can't seem to measure ANY detectable runout on the spindle .... maybe i got lucky ...
 
Well, they are monitoring the current for sure and probably the armature voltage too, so if you smooth the waveform it should still work the same way, I would think- you don't want to lose too much power in the output filter though- I'm sure there is room for improvement. If you can get ahold of some ferrite rods or E cores and some 16 to 18 gauge wire you could experiment, maybe cannibalize some PC power supplies. Try to pinpoint the noise first
 
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It's probably the wire coils and/or the core in the motor physically vibrating. I got a dose of that when I rewound a 60Hz transformer and jammed the core plates back in, not shellacking them like they were before. It made one hell of a buzzer, it did...
 
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