A.4.4.1 Electrical equipment hazards must always be understood.

A.4.4.2 Special care should be taken in the presence of hazardous mixed voltages (DC and AC) such as coils, DC power supplies and leak detector systems.

A.4.4.3 Remember that unpredictable voltages can occur in a faulty device. An open circuit of the discharge resistor may cause dangerous charges to remain on the capacitor. Therefore, the power supply should be turned "off" and all capacitors should be discharged before the bad capacitor is removed or before the test equipment is connected or removed.

A.4.4.4 Determine all voltage sources and current paths before measuring wiring, ensure that the equipment is well grounded and the fuses of the correct type are installed properly (see the relevant regulations of the National Electrical Code), and set the appropriate measurement range before turning on the power.

A.4.4.5 The open circuit and the lock circuit should be disconnected before the ohmmeter is used to detect and ensure that all capacitors are discharged.

A.4.4.6 It is necessary to verify the phase sequence of the power supply before wiring the electrical components such as the electric switch. The electric switch can only be operated after the inverter has been powered down. When the inverter power supply cabinet is powered on, it is strictly forbidden to be close to the switch and operate the switch.