EDM equipment is used to machine metal and other materials by
electrostatic discharge. The equipment does not utilize motors
except for coolant pumps, but rather the main use of electrical
power in the equipment is a rectifier that converts the utility
supplied AC power to DC.
Similar to three-phase motors, it is best to operate
three-phase rectifiers with balanced three-phase power.
Operating with unbalanced voltages can lead to damage of some of the
rectifier components, especially at full load, and severe imbalance
will increase the ripple current on the capacitors of the DC bus.
Too much ripple current can lead to damage of these capacitors.
A static converter must never be used to
operate a wire EDM. It will lead to damage of the
A phase converting VFD must never be used to power a
wire EDM because it contains electronics, thus capacitive loads.
The PWM voltage of a VFD will damage these
electronics. Rotary converters can be used with wire EDM, but the
shortcomings of these converters affect rectifier systems in much
the same way motor systems are affected. The variable amperage
demand from the EDM will result in voltage imbalance from the rotary
converter, leading to possible damage to the equipment or variable
Digital phase converters
can safely and efficiently operate EDM equipment because they
produce balanced voltage under variable load conditions and produce
sine wave voltage safe for operating solid state electronics.