Phillip, Bart,
sniperz:
----- Original Message ----- From: "bartb" <bartb@xxxxxxxxxxxxxxxx>
Hi Phillip,
The VFD receives 1 phase 240V power and outputs 3-phase 230V power to
the motor. The frequency is changed which changes the speed of the
motor. It all built in to the VFD. I simply use a small
potentiometer mounted on the control panel to vary the analog signal
and the drive takes this information and vary's the frequency
accordingly. The PLC is the brains, but it's mainly for errors. The
main reason I use it is that if the VFD gets an error of any type,
the motor will either stop within 5 seconds or freewheel to a stop.
The VFD outputs an error signal which I feed into the PLC. If there
are any errors, it will shut down the main contactor to the coil.
While I was at it, I threw in a deadman switch (low level signal),
enable key, etc.
Adam Minchey also runs 3-phase via VFD on his coils. One could also
use a DC motor and simply vary the voltage for bps control.
Yep, I use a permanent magnet DC treadmill drive motor powered through
a variac and a FWB rectifier, which pretty
much gives an infinite range of speed control. Not quite as many
"bells and whistles" as is available with a VFD drive system
but never the less, it still gets the job done ;^)
Take care,
Bart
David
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