| Electronics > Repair |
| APC Smart-UPS 1500 (SMT1500) |
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| Bretterson:
--- Quote from: fmashockie on May 03, 2024, 09:00:06 pm ---MV2 is a MOV (metal oxide varistor). There are other MOVs on the PCB that you can check to see what kind it is. It is very likely the same as ERZ-V14D471 --- End quote --- Right, I know it's a varistor. I'm fairly certain it isn't the same one because the outline for that space is larger and the component looks larger in this picture from one that sold on eBay: https://i.ebayimg.com/images/g/sgEAAOSw~CZltAdV/s-l1600.jpg --- Quote from: fenugrec on May 03, 2024, 10:00:30 pm ---You may be able to cobble something with an incandescent bulb (say 100W) in series with the battery as a current "limiter". May prevent the UPS from working properly but would reduce risk of a catastrophic short. --- End quote --- Oh cool, I'll definitely look into that. Thanks. |
| fmashockie:
--- Quote from: Bretterson on May 05, 2024, 05:03:38 am --- --- Quote from: fmashockie on May 03, 2024, 09:00:06 pm ---MV2 is a MOV (metal oxide varistor). There are other MOVs on the PCB that you can check to see what kind it is. It is very likely the same as ERZ-V14D471 --- End quote --- Right, I know it's a varistor. I'm fairly certain it isn't the same one because the outline for that space is larger and the component looks larger in this picture from one that sold on eBay: https://i.ebayimg.com/images/g/sgEAAOSw~CZltAdV/s-l1600.jpg --- End quote --- My apologies I made a mistake. MV4 is the same as those with the heatstrink on them. MOVs have a few main parameters: Voltage rating (AC/DC) Clamping Voltage Peak surge current The MOVs are to protect from surges when the UPS is being powered normally and for protection to the inverter when the UPS battery is being used. In some models there will be MOVs on the both the neutral and live rails of the circuit. When a surge occurs that exceeds the clamping voltage of the MOV, it will go low impedence and short the current to ground (that is why you will notice on your PCB one leg of the MOV is on the Live or Neutral rail and the other is on Ground). This MOV MV2 not being there isn't going to prevent your UPS from working. As I said earlier, these things are very dangerous to work on. You might want to invest in some additional equipment (DC benchtop supply, scope, etc) as well as gain a bit more experience in troubleshooting before proceeding. |
| asis:
Hi, All MOV's parameters: https://datasheetspdf.com/pdf-down/E/R/Z/ERZV20D471_Panasonic.pdf It should be taken into account that the UPS design can be either 220V or 120V; accordingly, the ratings of certain components may be different. It is possible that if at the time of the incident the UPS was in operation and sticking (burning) of the RY1 relay contacts could occur; RY2; RY3; RY4; RY6; RY900. It would be appropriate to check the condition of their contact groups, or better yet, dismantle them and check them individually. You should also separately check the status of the MOSFET's of the inverter and the operation of the charger. There are several threads on the forum that describe how to do this. - The rating of capacitor C53 for UPS in AC220V version is 2.2mF x 275V~. |
| flaotte:
--- Quote from: fmashockie on May 03, 2024, 02:15:59 pm ---Some advice when working on UPSs: do NOT use the battery to troubleshoot/perform testing. Those batteries can release uncontrolled amounts of current if there is a short somewhere on the board. It can be very dangerous. Use a DC power supply with current limiting capabilities to simulate the battery. --- End quote --- is there any safe (safer) way to debug mains part of such device? |
| fmashockie:
--- Quote from: flaotte on May 06, 2024, 09:29:54 am --- --- Quote from: fmashockie on May 03, 2024, 02:15:59 pm ---Some advice when working on UPSs: do NOT use the battery to troubleshoot/perform testing. Those batteries can release uncontrolled amounts of current if there is a short somewhere on the board. It can be very dangerous. Use a DC power supply with current limiting capabilities to simulate the battery. --- End quote --- is there any safe (safer) way to debug mains part of such device? --- End quote --- The precautions one should take for checkin the mains portion or SMPS of the UPS are the same precautions one should take when working on any device powered by mains voltage. -Be careful when checking HV side or primary side -It might be benefical to use a lamp series tester to protect from unknown shorts on the primary side -If you plan to use a scope, make sure the unit is plugged into an isolation transformer. If you plan to probe mains, you should only use methods that are safe - such as a HV differential active probe. Those are just a few precautions one should take. But the main thing that separates the UPS from other devices powered by mains is the UPS's battery which is usually two large 12VDC batteries in series that can deliver large amounts of current. Keep in mind most of these devices are rated to deliver upwards of 1000W - that's a lot of power. And a large battery that can deliver a lot of current is required. If there is a short on the board in the charging or inverter circuit, this power can be delivered uncontrollably which could cause serious damage to life/property. I've seen APC UPS units with shorts on the inverter MOSFETs that caused catastrophic damage and the battery protection fuses did not prevent this damage (I've done a few videos/threads on these topics). So that is why I voiced my concern for troubleshooting these units without a DC power supply with current limiting. |
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