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EP series UPS fault maintenance has some specificity, especially EP series UPS fault code inquiring method, make the maintenance more clearly oriented. Combine the fault code inquiring and LED, LCD displayed on the panel, can basically confirm UPS failure part.

Failure phenomena of EP series UPS are very different, might not enumerate one by one. The followings are only experience summarized in locale maintenance. They are mainly the case analyses.

Internal Fault 1

This fault usually happens when change the system board, because forget to insert the power configuretion board (NF12223). Once close the SWBY, fault code will be displayed on LCD. Some faulty phenomena relevant to power configuration board are illustrated below:

Problem: install one EP30KVA new UPS unit, find the LCD displays “RT15”, why?

Because power display signal is from power configuration board. If it is not connected to system board, will influence the display.

If power configuretion board is not inserted on the system board, what will happen?

Phenomena: The machine gets power, after the panel displays normally, you can see Internal fault 1.

It is usually because the power configuration board is not inserted or loose. Insert the configuration board or plug it again.

Internal Fault 2 Inverter fault

The machine works on bypass mode, LCD displays Internal fault 2 i=XXXX XX

This information is inverter fault. When carry out maintenance, close SWMB manual maintenance switch, open SWIN/SWBY/SWOUT, discharge the capacitance.Then check and measure as the folllowing steps:

a. Close SWBY once again, check D13 / D29 of each inverter driver board, blink or not. b. Measure the fuse F1 / F2 on each inverter driver board, burn out or not.

c. Measure IGBT driver terminal, break down or not.

d. Measure three phases inverter output fuses, burn out or not.

e. Check connection of output AC capacitance, loosen or not, burn out or not. f. Check relavant connection of inverter part, loosen or not.

g. Change inverter control board. Cases:

1) EP 80KVA

Loud noise of UPS, especially noise of fan, it switches to bypass mode now, LCD displays “Internal fault 2, i=0201 08”, where is the fault?

Go to the locale, close SWMB, restart up UPS, after self-checking, it shows internal fault 2, i=0201 08. After discharging, check and find fuse F1 of Phase 3 driver board, it has burnt out.

Change the fuse and fan, restart up, UPS operates normally.

2) EP 30 KVA

UPS bypass mode, buzzer sounds long, LCD displays “Internal fault 2, i=0403 08”

Mainly check and measure inverter part as the above steps, corresponding fault information of 0403 clews: lockup by card or module IGBT 2 in inverter. Measure by multimeter, find connecting wire of Phase 2 output filter capacitance has broken. After changing it, restart up, UPS operates normally. It’s caused by poor contact of connecting terminal.

3) EP 40 KVA

One 20KVA UPS unit reports “Internal fault 2, i=8001 0A”, the reason?

Corresponding fault code clews: lockup by card or module IGBT 3 in inverter.

First mainly check the the fuse and inverter module of Phase 3 inverter driver board, break down or not. After the measure, find one side of Phase 3 inverter module has broken. Change it, then measure IGBT of the other two phases, it’s OK. Restart up, UPS operates normally.

4) EP 60 KVA

UPS shows Internal fault 2, i=A001 08. Why? Fault code clews: Error at inverter power supply!

Measure D21 and D20 on power supply board, find there is no output voltage. Power off, measure D21 and D20 by the multimeter, find them broken down.

Change power supply board, UPS operates normally! Internal Fault 3

When this fault happens, it may be caused by the following aspects:

a. TLI winding is short. Measure the resistance of winding, the normal value is 3KΩ or so. TLI winding power wire is well connected to No.5 and No.6 wire of J7 on interface board or not.

b. Poor connection from auxiliary contactor of TLI to J7 of interface board. Mainly check the connection from No.3 and No.4 wire of J7 to TLI winding.

c. Interface board is faulty. Internal Fault 4

Rectifier fault

When this fault happens, it may be caused by the following aspects: a. rectifier control board is faulty.

b. rectifier driver board is broken. Internal Fault 5

When this fault happens, it may be caused by the following aspects: a. One of the three phases input fuses on bypass board is burnt out. b. SCR (bypass board) fault.

Cases:

One 40KVA unit is operating normally, suddenly inverter output indicator blinks, then switch to bypass mode. Bypass indicator is blinking, and Internal fault 6 shows on panel. Restart up, blank screen.

This fault happens most on units produced before 2006, the main reason is capacitance C4 on power supply board is ineffective. Change power supply board, restart up, UPS operates normally.

When UPS displays the fault:

1. Measure UPS bypass input three phase fuses, and fuse F7, F3 on bypass board, burn out or not.

2. Measure the voltage of D1/D7/D8/D19/D20/D26/D27/D35 on power supply board, normal value: ≥15vdc.

Internal Fault 7

When this fault happens, it is mainly caused by poor connection of voltage feedback signal wire on inverter control board.

Internal Fault 8

When this fault happens, it may be caused by the following aspects: a. rectifier control board is faulty.

b. Absorber circuit on rectifier driver board is faulty. Internal Fault 9

When this fault happens, it may be caused by the following aspects:

a. TLB winding is short. Measure the resistance of winding, it is about 3KΩ or so.

TLB winding power wire is well connected to No.4 and No.6 wire of J7 on interface board or not.

b. Poor connection from auxiliary contactor of TLB to J7 of interface board. Mainly check the connection from No.1 and No.3 wire of J7 to TLB winding.

c. F6 of bypass board is burnt out or not. c. Interface board is faulty.

e. Main system board is faulty. Case:

Before delivery, after loading and aging test, when get ready to package, start up UPS, it reports Internal fault 9. Why?

Check as the above steps, have not found suspicious point. Check the connection from TLI to interface board, measure again, find No.1 and No.3 of J7 to TLB winding is not well connected. It may be the wire problems which result in the poor contact. Change the wire, UPS operates OK!

Cases:

Inverter mode operates normally, but sometimes report internal fault 10 and switch to bypass mode. Why?

This failure is mainly because of the connection / poor contact of system control board and inverter control board. Re-plug the connection terminal between J3 of system control board and J7 of inverter control board, and the CPU of two control board. Measure the voltage of D19/D20/D26/D27/D35 on power supply board, should be ≥15vdc, and voltage of D82 ≥ 12vdc, voltage of D91 ≥5vdc.

If it still have problems, change the tow control board. Internal Fault 11

The failure represents: After closing SWIN / SWBY / SWOUT of UPS (that is after starting up), press 2 - 2 can see I = 2204 40 (this parameter indicates that the inverter operates normally), rectifier and inverter both have been started up, it is on bypass mode. When it is on inverter mode, TLI and TLBY contactors switch back and forth!

The probabilities caused the failure are: a. bypass board is broken.

b. main control board is faulty. c. Interface board is faulty. d. null line is poorly connected. Cases:

EP 60KVA

One of the two parallel UPS units, usually reports Internal fault 11, but after the engineer arriving at the locale, restart up and UPS operates normally. Why?

After the inverter start up normally, use the multimeter measure the voltage difference between TLI and TLBY, find that after the switch failure, it’s about 20 VAC more than the maximum allowable value. Even change the main control board and bypass board, it’s still not improved obviously. It may be caused by poor contact. Check the connection of UPS again, find that output null line among the main circuit at connecting terminal is poorly connected, connect and fasten it, start up UPS and it operates normally!

Briefly analyze: because of the poor connection of null line, resulting in the public

reference point of bypass circuit and inverter output circuit is offset, there exists greater voltage difference, that is not synchronized. At inverter mode there must be voltage difference ≥20VAC, by the feedback, the program identified as beyond the scope of synchronization, will not switch.