The HD4 Breaker Testing Unit is designed to be used for the testing of Medium Voltage Circuit Breakers. The panel contains an 110VDC output, ammeter, switches, fuse holders and fuses. The unit contains the standard mating connector for the user to connect to the HD4 circuit breaker. This unit is also compatible with the VD4 and HPA-HD4 hybrid circuit breakers and can be customized for different breaker configurations.