EX2000 Fault : ST 717_ _PS AC IN and FL 711_ _MCP SYNC


Thread Starter


Dear experts,

We have EX2000 with static exciter type (Our EX2000 have two systems: Primary and Back up Module) that have some alarms in back up module while the unit is on operation.

These alarms are:
1. ST 717_ _PS AC IN
2. FL 711_ _MCP SYNC

We already checked the cables' tightness and also replaced some cards on the back up module when the unit was shutdown. The cards that we had replaced were:

But the alarm is still appeared until right now.

From this forum, we would like to asking your help, what kind of action that we should do to solve the problems?

I am sorry for my poor English, and looking forward for your help.

Thank you
We also have the same error code 717 on our EX2000. We changed the DCFB board but that did not clear the problem. The power supply is online. The EX2000 is online and running.



> We also have the same error code 717 on our EX2000. We changed the DCFB board
> but that did not clear the problem. The power supply is online. The EX2000 is online and running.

Dear Mr. Jakubin

Thank you very much for your response. may I know which module that have these alarm? Primary (Main) or secondary (backup) module or protection module?

At our excitation system, these alarm is appeared on backup module, so our excitation is still running because the main module takes control. We are still worried because based on EX2000 manual book, these alarm can cause trip fault.

In my experience, these two alarms are tied together. The FL711 is sometimes driven by the fact that the 717 fault is in. The 717 fault indicates either a problem with the AC input, AC power supply, or the sensing circuit for the AC input.

It looks like you replaced the cards for the sensing circuits, but did you check for the actual 120 VAC power source? Does your system have the three 480 volt blowers for each core? If so, have you checked the blower motor transformer (BMT) fuses? Are the blowers running on the core with the fault? It could be a blown fuse on the transformer or a bad transformer. You should be able to measure 120 VAC between terminals 19 and 20, and terminals 21 and 22 on the blower motor transformers.

If you don't have the 480 volt blowers, there should be another set of transformers for the power supply. They are usually labeled PST1 and PST2 and will have fuses associated with them. Check the fuses and the outputs of these transformers for proper AC power. They should have 120 VAC between terminals 1 and 2, and between 3 and 4.

The main power for the 480 volt circuit to the BMT1 and BMT2 is usually fed from the 41AC breaker through the AC disconnect on each core. This may sound stupid, but have you checked the AC disconnect on the core that isn't working?

Some of these circuits have 480 VAC feeding into them. These checks should only be done by a competent electrician. Be sure to take the proper precautions to ensure personnel safety.

Let us know what you find.


Dear Brian Hall

Thank you very much for your response. We will inform to you ASAP, and We are really sorry for our late response.

Thank you


Dear Brian

We already checked about the power supply system such as:

1. We have checked all of Control core no. 1 and 2 Fuses which related to the power supply. There are: Fuses for Fan Blowers, FU1, FU2, FU3, LFU, PFU, BMT2FU, PSFU2 and the results are normal.
There are no evidence about broken fuse or loss of power supply.

2. We also have replaced the SLCC card for control core no. 2

But the alarm ST717 still active. Maybe you have another experience, where can we find the source of the alarm? Could it be from SDCC, or IO board? Or maybe something happens with cable ribbon?

We are still confuse until know.

Kindly help us

Thank you