SMA Manual Explanation
|Error No.||Explanation||Corrective measures|
|7707||Contactor error at the AC disconnection point.|
This fault is an AC contactor error that the inverter produces if it does not detect the AC contactor closing during startup or operation. It's imperative to check for current. If current is flowing through the contactor then it's functioning correctly, even if it only happens for a second. The likely issue is that the relay signal isn't operating correctly.
The most common cause of this issue is the auxiliary relay on the side of the AC contactor. It either has loose connections, or the component itself is wearing out.
- Check for loose connections at the auxiliary contact of the AC contactor.
Check for Loose wires or connections on control board of the inverter. The 500HEUS has the relay output on X5 of the mmtcon board.
Open the DC contactor and inspect the connection points on the internal AC contactor board to ensure all wires are landed correctly. Any disconnection can cause the inverter to not start at all and additionally throw a fault.
To determine if the AC contactor is GOOD, you can engage it manually using the PLC switch on the side of the contactor. This will automatically close the inverter if it has AC power. The inverter should be keyed off, and the DC should be turned off when this procedure is performed. There is a small percentage of risk when testing the contactor this way, but it can determine if the contactor is good or bad quickly.
Next check the K60 relay located next to the timer relay, try replacing the k60 removable relay with the K20 removable relay. They are both rated for 230V. If the relay has failed the AC contactor will not respond to the 24V input from the MMTCONT board. This will determine if the relay is good or bad. The brown wire in the photo goes to the side of the AC contactor and sends a 24v signal to the AC contactor telling it to close. A failure at this relay will cause the AC contactor to not respond to the close signal.
Past Causes of the Issue
- 7707 - Intermittent failure, the A2 connection on the board was not securely attached, and was causing an intermittent 7707 fault to happen throughout each day. The inverter was found running, but an inspection was performed anyways. This connection was found as seen in the picture.
- 7707 fault behaved similarly to other solutions, but eventually caused a hard fault that could not be recovered from. Inverter went through its normal start up cycle - Wait 300 seconds, close DC contactor, IGBTs fire up, and then the DC contactor opens. The AC contactor never closes. The internal AC contactor control board NEVER receives the 24V signal to close. We found the K60 relay (which is responsible for sending the close signal) had a faulty relay. This site had previously experienced a grid event that likely caused this relay to be damaged. It slowly failed over the course of 4 days. After replacing the K60 relay the inverter came back online with no further issues.