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How do I fix an F51 (Ext Fault) code for a 9000X Series drive?

The external fault on this drive is mainly from temperature switches. There are 3 temp switches in the phase shifting transformer and one temp switch on the external rectifiers. On FR10 and above drives, this is normally all that there is so you would be looking for one of these to be tripped. If one of them is tripped you will have to investigate the reason for it. On FR9 and below you also have an interlock on the precharge contactor added into this. If the drive trips on external fault only when you try to start the drive it probably is this interlock that is causing it as there is a normally closed run contact across this so it does not look for this until you try to start. If it is the precharge or inverter contactor the first thing to look for is to make sure the 24VDC supply is working. There is an indicator light on top of it that indicates normal operation. The next thing to look for is to make sure that the contactor is being asked to pull in. Check to make sure there is 24VDC from the negative (-) connection to the positive (+), permissive (P) and forward (F) connections. If you are missing voltage on any of these troubleshoot that circuit. The (+) connection should be coming directly from the 24VDC supply. If you do not have a bypass the (P) connection will be jumped to the (+) connection. If you do have a bypass the (P) connection will probably come from a NC aux contact on the bypass contactor or a contact off of the bypass select relay. The (F) connection should come from the CRI relay which is a 24V relay run off of the digital output on the OPTA9 board, this output should be set to charge switch state and not ready so that this output only reacts to the DC bus level. If you have voltage on all of these it is likely that the contactor is bad.