Originally Posted by
jimcolt
You can easily do this experiment....connect a DVM (digital volt meter) to the terminals J15 and J16 in the Hypertherm Powermax system. Set the meter on a DC scale with a range of up to 300 volts. Fire the plasma torch and cut at a fixed speed....raise the torch....read the voltage on the meter, then lower the torch, read the voltage on the meter. You will notice the voltage rises as the arc length gets longer and lowers as the arc length gets shorter.
In a torch height control....the circuitry monitors this voltage and adjusts the torch height by driving the z axis motor up or down to maintain the correct voltage, consequently you can use this to control torch height. The voltage divider is used to isolate and filter this signal from the plasma, bringing it down to a useable level that can be used by a comparator circuit that compares the actual arc voltage to a known voltage......and then adjusts the torch height to compensate for plate that is not perfectly flat. Conventional plasmas need to maintain the correct torch to work distance within plus or minus .020"....or within about 5 arc volts. With High definition class plasmas, torch heigh must be maintained to plus or minus .004" of the ideal height, or within 1 arc volt.
I don't understand why you want to ground anything from the plasma directly to the drive motor.....
Jim