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4.4 IGBT Enable
In all elevator applications, an Output Contactor is installed between the inverter output U, V, W and the motor. In an emergency, the Safety
Line is opened due to an unsafe condition and the Output Contactor disconnects the power from the inverter to the motor (the motor brake is
also applied at the same time). When the Output Contactor opens with current flowing through to the motor (inverter IGBTs are active), there will
be arcing in the Output Contactor depending on the motor inductive energy. Arcing of the Output Contactor can reduce the lifetime of the
contactor and in some severe cases can damage the contacts poles. Therefore it is recommended to electronically switch off the inverter IGBT
firing circuits before opening the Output Contactor (milliseconds later). The inverter IGBT firing can be electronically switched off with the
"IGBT Enable" function as shown in the timing charts below.
CAUTION: An Output Contactor MUST always be installed as the final safety power cut off to the motor. The "IGBT Enable" function is NOT a
substitute for an Output Contactor, it is designed to work together with the Output Contactor.
* MC reaction time: the reaction time of output relay of MC.
For some applications, the status of output contactor needs to be checked before inverter starts up, hence one relay output of MC will feedback to IGBT Enable (above in the
diagram it is DI6).
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