Operation principle and hardware description 43Main disconnecting device [Q1.1]Depending on the configuration of the drive, the main disconnecting device of the drive iseither a switch-disconnector or a main circuit breaker. Units with a switch-disconnectoralso have a main contactor.The main disconnecting device switches the main supply to the drive on and off. Todisconnect the main supply, turn the switch-disconnector to the 0 (OFF) position, or rackout the main breaker (whichever device is installed).WARNING! The main disconnecting device does not isolate the input powerterminals, AC voltage meters, or the *auxiliary voltage circuit from the power line.To isolate the auxiliary voltage circuit, open the auxiliary voltage switch (Q21). Toisolate the input power terminals and AC voltage meters, open the main breaker of thesupply transformer.*With frame 1×R8i + 1×R8i units, the main switch-disconnector [Q1.1] also switches the auxiliary voltage onand off.To close the main disconnecting device, auxiliary voltage must be switched on, and thegrounding switch (if present) must be open.Auxiliary voltage switch [Q21]The auxiliary voltage switch controls the supply to the auxiliary voltage transformers. Thetransformer feeds the control circuits inside the drive such as cooling fans, relays andmeasuring equipment. The switch is fitted with fuses.Note: Frame 1×R8i + 1×R8i units are not fitted with an auxiliary voltage switch. Theauxiliary voltage is switched on and off by the main disconnecting device [Q1], andprotected by fuse disconnectors F20.1…F20.3.Grounding (earthing) switch [Q9.x], optionalThe grounding switch [Q9.1] (option +F259) connects the main AC power bus to the PEbusbar.To close the grounding switch, auxiliary voltage must be switched on, and the maindisconnecting device must be open.WARNING! The grounding switch does not ground the input power terminals ofthe drive or the auxiliary (control) voltage circuits.Charging switch [Q3]The DC capacitors of the drive must be charged smoothly before the drive can be started.A charging circuit is provided to limit the charging current with resistors until the capacitorsare charged and main contactor/breaker can be closed.Charging is enabled using the charging switch [Q3] – the charging itself is controlled by thesupply control unit. The switch must be kept closed during operation.Other devices on the door• Voltmeter (option +G334); comes with a phase selector switch. Note: The voltage ismeasured on the supply side of the main switch or breaker.• AC current meter (option +G335) on one phase.
