Yes the power resistors are in the 100V supply. Between the filter cap and the charge mosfet.
The PWM allows the duty cycle of the frequency to be controlled, in effect controlling the amperage. There are no inductors involved. The discharge is a spark gap in a dielectric oil.
As the discharge starts, the voltage in the gap ionizes a path in the oil. This then allows the current to start to flow, dropping the voltage to about a third of the open voltage. This current creates a temperature of ~3000 degrees F melting a small crater of metal out. The PWM then shuts down the flow of electricity, and the oil flows in and washes the gap clean and the process starts again.
This process, EDM has been around since right after WW2.The first ones were RC oscillator circuits. Using high value resistors and caps with the gap resistance controlling discharge. They worked but didn't give any real control of the machined finish.
The first pulsed machines used a rotating disc with contacts on it mechanically controlling the frequency and duty cycle. They didn't work very good. This was late 50's early 60s.
Then came the style I'm trying to replicate. Smaller cap values and adjustable frequency and duty cycle. But in my logic circuit I'm adding the isopulse to control the gap voltage better, to give a better finish to the machined part.
There is also a voltage comparator/servo that keeps the electrode at the correct distance as the metal is removed. That part of the machine is done, just need to work out this spark generator circuit now.
The PWM allows the duty cycle of the frequency to be controlled, in effect controlling the amperage. There are no inductors involved. The discharge is a spark gap in a dielectric oil.
As the discharge starts, the voltage in the gap ionizes a path in the oil. This then allows the current to start to flow, dropping the voltage to about a third of the open voltage. This current creates a temperature of ~3000 degrees F melting a small crater of metal out. The PWM then shuts down the flow of electricity, and the oil flows in and washes the gap clean and the process starts again.
This process, EDM has been around since right after WW2.The first ones were RC oscillator circuits. Using high value resistors and caps with the gap resistance controlling discharge. They worked but didn't give any real control of the machined finish.
The first pulsed machines used a rotating disc with contacts on it mechanically controlling the frequency and duty cycle. They didn't work very good. This was late 50's early 60s.
Then came the style I'm trying to replicate. Smaller cap values and adjustable frequency and duty cycle. But in my logic circuit I'm adding the isopulse to control the gap voltage better, to give a better finish to the machined part.
There is also a voltage comparator/servo that keeps the electrode at the correct distance as the metal is removed. That part of the machine is done, just need to work out this spark generator circuit now.