High Voltage Variable DC Technology Safety Mechanisms & Arc Protection
In low voltage applications (>600V), a short circuit results in an arc flash, and contact can be fatal. Consequently, the architecture differs fundamentally from standard bench supplies.
In low voltage applications (e.g., 30V), accidental contact causes a minor short circuit. In high voltage applications (>600V), a short circuit results in an arc flash, and contact can be fatal. Consequently, the architecture of high voltage programmable supplies differs fundamentally from standard bench power supplies.
Output Discharge Circuits (Bleeders)
A high voltage power supply is essentially a capacitor charging engine. Even when the AC input is removed, the output capacitors retain charge.
Industrial units utilize an active discharge circuit (or "crowbar" circuit). When the output logic goes to "OFF," a relay engages a power resistor across the output terminals.
The discharge time must be calculated to bring the voltage to safe levels (<50V) within a specified timeframe (typically <10 seconds for rack units).
Arc Detection and Protection
During insulation testing or capacitor manufacturing, the dielectric material may fail, causing an arc.
The Risk
A sustained arc generates intense heat, carbonizing the test fixture and potentially damaging the power supply's output stage.
The Technology
Digital HV supplies monitor the rate of change in current (di/dt). A sudden, non-commanded spike indicates an arc. The DSP (Digital Signal Processor) immediately inhibits the PWM drive signal, shutting down the output in microseconds—faster than any thermal fuse can react.
Galvanic Isolation
Connecting a 1000V power supply to a PC via USB creates a path for high voltage to enter the computer's logic board if a ground fault occurs.
Requirement
Professional programmable supplies use optical or magnetic isolation on all communication ports (RS485, LAN, USB). This ensures the high-voltage ground is floating or strictly separated from the logic ground.
Safety features are not optional
When evaluating equipment, verify the existence of active discharge and isolation specs.