[Jet A]

Hello,

Let me give you some specs.

Bridgeport Series 1 2hp
cnc4pc c11g breakout
mach 3 control software
vfd-hitatchi x200 2hp

What i am attempting to accomplish is use the step pulse to pwm generator on the c11g board. I have sucessfully got a voltage range from .5vdc to 8.8vdc.

The problem, When i ramp down the speed to much the vfd errors out. The error code state "dc bus current to high" overvoltage protection.

I cant seem to find a good setting in the vfd that prevents this. Anybody have any good tips? vfd works fine with the face potentiometer

[H.O]

When the motor slows down it converts the energy stored in the rotating mass to electricity that goes back into the capacitor bank in the VFD causing the voltage across it to increase. To protect the semiconductors in the VFD it shuts down when the voltage gets too high.

Try lowering the acceleration for the spindle in the motortuning dialog in Mach3. There may also be a setting for acceleration/decceleration time in the VDF, perhaps there are different settings for the local (pot) and remote (0-10V) control inputs.

The VFD may have brake chopper built in. This can be set up to "load" the DC-bus when the voltage starts to increase which helps break the motor and keep the voltage from increasing. Some VFDs have the break-resistor built in, on some you need to connect it externally - check the documentation on the VFD.

/Henrik.

[Jet A]

hmm...good point on that. Never thought about turning down the acceleration inside mach. I will give the dc brake setting a shot as well.