APC SMT 3000RMi2u - Page 1
Forum section: electronics / repair

author: sdav94
author_rank: Contributor
timestamp: July 30, 2022, 09:19:38 pm
content: Deal all professionalsI have apc smt3000RMI2U suddenly stopped working when I checked there are some mosfets burned into two pieces. There are 16 mosfets by fairchild FDP3651U.I replaced mosfets and 20 ohm 16 resistors hip4082ibz 361-0015AG 361-0025V2. And after when I connected 48V DC batteries it turned on but when i turn on inverter mosfets burned again i checked all small resistors 2R2,20R0,390 but no luck. Already replaced those IC 3 times and twice all Mosfets kindly please help.Thank you

author: TheMG
author_rank: Frequent Contributor
timestamp: July 31, 2022, 12:41:22 am
content: I would investigate whether the MOSFETs are being driven correctly.Remove all the MOSFETs (this makes it possible to troubleshoot without burning anything up). Power up the UPS inverter while watching on an oscilloscope for the drive waveform at the gate connections of each MOSFET bank.You may have to use single-shot capture on the scope as the UPS will undoubtedly only try to power up the inverter for a short time before going into a fault condition.Quite likely the reason the MOSFETs are failing is that they are not being switched correctly (either faulty gate driver or logic fault). The configuration is an H-bridge. If the high and low side of the H-bridge get switched on simultaneously... POOF!

author: alex_pescaru
author_rank: Contributor
timestamp: July 31, 2022, 09:02:11 am
content: Besides the good advice above, you may want to also check the integrity of the transformers for possible internal damage.As they are low freq (50Hz) transformers, you can easily connect them individually to some form of low voltage alternative source (24v or about) and check to see if their voltages are consistent.

author: sdav94
author_rank: Contributor
timestamp: July 31, 2022, 09:46:17 am
content: well i didn't connect transformer yet and i am just putting 4 mosfets each line one FET only for testing and giving 48VDC so if everything will be okay i can get around 50 to 55V AC from Mosfets. can you please tell me HiP4082 input voltage on SMT3000 board. 361-0025V2 is fine and 361-0015AG i have doubt but main driver for mosfets is 4082 that's why mosfets are burning please send me details of hip4082 current volts on pins thanks.so it will easy for me to figure out.however, i have changed all 20 ohm resistors and R167,and R173,R168,R174 these resistors are directly connected to BHS AND AHS from mosfets.

author: sdav94
author_rank: Contributor
timestamp: July 31, 2022, 09:50:09 am
content: well i don't have oscilloscope just i have small electronic lab have multimeter and some other basic stuff any chances that i am able to repair without oscilloscope?

author: sdav94
author_rank: Contributor
timestamp: July 31, 2022, 09:53:20 am
content: Quote from: TheMG on July 31, 2022, 12:41:22 amlets say if logic fault what should i have to check?

author: sdav94
author_rank: Contributor
timestamp: July 31, 2022, 12:23:49 pm
content: smt3000 have 4 sections of mosfets each section have 4 mosfets so I installed only 1 mosfet on each section without transformer to just check output AC voltage.

author: alex_pescaru
author_rank: Contributor
timestamp: July 31, 2022, 02:10:21 pm
content: Quite difficult to verify things without an oscilloscope, because you can't verify if the HIP4082 outputs are correct and not overlapping, which as TheMG said, is fatal...And the voltages about you've asked, aren't of any use to you, because all signals are PWM signals and with a standard multimeter is difficult to diagnose.Also don't blame only HIP4082 for burning the mosfets... It only replicate/amplify the signals it gets.For a description of this kind of UPS principles you can take a look at this, using Google translate:http://www.mirpu.ru/ups/84-shemups/146-su1000.htmlAlso, a schematic pretty close with what you have is:http://www.mediafire.com/file/aro51tm0krudbka/APC_640-7732H_SMART-UPS_1500.pdf/fileBy the way, from where did you find and bought the SMD version of HIP4082? Because I've managed to find only the DIP version and I had to improvise...In fact, if it isn't too much, where did you find all the ICs you said you replaced three times?

author: sdav94
author_rank: Contributor
timestamp: July 31, 2022, 04:01:39 pm
content: Quote from: alex_pescaru on July 31, 2022, 02:10:21 pmhttps://shop.ectransistors.com/they are good you can find replica and original alll components here and normal delivery cost 8$ and within 10 to 12 days you can receive shipment.

author: sdav94
author_rank: Contributor
timestamp: July 31, 2022, 04:10:04 pm
content: Quote from: alex_pescaru on July 31, 2022, 02:10:21 pmI can't find Q911 Q912 Q914 on schematic can you help please?

author: alex_pescaru
author_rank: Contributor
timestamp: July 31, 2022, 09:48:06 pm
content: Those are some additions for the SMT series with "Green Mode". The schematic I've indicated is for the SUA series.Those transistors, together with the reverse diodes from mosfets, are used for charging the battery in "Green Mode".Check this schematic posted by Vladimir:https://www.eevblog.com/forum/repair/apc-smartups-overload/?action=dlattach;attach=1533148The shop you indicated is not sending to any EU countries...

author: sdav94
author_rank: Contributor
timestamp: August 01, 2022, 03:18:42 pm
content: Quote from: alex_pescaru on July 31, 2022, 09:48:06 pmwell i am from Dubai so if you can afford both way shipping i can help you with that.