ups as inverter - inverter electronics / again

fca1fca1 Solar Expert Posts: 124 ✭✭
hi there im just trying to understand why my studer consumes 8w when on idle and my ups apc 1500 30w and even worst i have now sua3000 that works at 48v consume 2amps with not load.... how can it consumes 100w just to be on ...

all ups, inverter that i see have electronic board and then big transformers... can any one explain the basics of inverter electronics boards/transformers...

what is consuming energy in idle ? the transformers ? i already turned off the fans and the control board ethernet but the apc3000 still consuming 1.7 amps...
this sua3000xli have 2 big transformers and huge heatsinks on some transistors....

what can i look for reducing the consumption in n idle ...



  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: ups as inverter - inverter electronics / again

    It's all that electronics sitting there "at the ready", warmed up and waiting, watching the line Voltage, keeping the batteries charged ....

    Off-grid inverters do much the same thing: left "fully on" they will chew up 20 to 40 Watts even though there is zero load on them. This is the "overhead"; the power needed to run the equipment that makes the conversion. It's why some units have standby mode, wherein most of the electronics is shut down leaving only a small monitoring system active which regularly "looks" for any loads present on the output (usually by pulsing the whole system every so often).

    As a rule, the bigger the inverter/UPS capacity the more power it is going to consume even when doing nothing because the components needed to handle that power use more themselves. Think of it like this: a small relay capable of switching 12 Volts at 500 mA is going to have a fairly low draw for the coil. If you need a relay that can carry 120 Volts @ 15 Amps it is going to have a coil that will draw much more current to activate (due to heavier contacts, larger gap to break, heavy spring to overcome). That's just a switching relay. The electronic components have to function along much the same lines: a FET capable of handling 20 Amps will itself consume more power than one for 5 Amps. Et cetera.
  • fca1fca1 Solar Expert Posts: 124 ✭✭
    Re: ups as inverter - inverter electronics / again

    Even So don't understand what can consume 100w ..
    My studer in full on not in standby consumes 9w ..

    So the MOSFET consume power just to be on ?
    Don't get it ..some bad design or not paying attention to this because ups should be normaly not in battery ..
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: ups as inverter - inverter electronics / again

    All components, if active, consume power. Voltage applied to the circuit becomes current flowing through the components (each of which has a resistive value) and thus Watts used. The fact is some of the circuits are better designed than others, so you can have a 2kW Outback that uses 20 Watts or a 2kW Samlex that uses 30 Watts. This phenomenon is not limited to inverters; you can see the same efficiency difference in any type of electronic device from cameras to computers.

    When a UPS unit is not running on battery it is still running because it has to keep those batteries charged and monitor the AC going through it to make sure it's still there.
    Curiously, the whole thing can be solved with a simple relay which would only energize the UPS when AC failed. Why don't they do this? Because the switchover would have a noticeable drop-out, which is sort of what you want the UPS to prevent!

    Continuous converting UPS systems are even worse, because they actually run "on battery" all the time: converting the AC to DC, keeping the batteries charged, then converting the DC back to AC to run things. Very clean continuous power, but it comes with a price.
  • fca1fca1 Solar Expert Posts: 124 ✭✭
    Re: ups as inverter - inverter electronics / again

    Hi yes I understand all that you are saying ..
    Just trying to see where most of the power is going..
    I measuring the 2 amps getting out of the bats when in batteries ...
    In fact when ac in is avaiable and batts are charged the consume is about 20w
    So when on batteries is where the self consume rises ...
    Just trying to understand where the major part of the power is going ..
    The sua3000 is interactive and not double conversion..
  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Re: ups as inverter - inverter electronics / again

    FETs and other devices have capacitance, which you have to charge then discharge 60 (or 120) times a second. Larger/more FETs, more capacitance, more to charge/discharge. Similar with inductors/transformers... They only work with "changing" current--Which causes "circulating currents" in the transformer core, and you also have I2R losses (self heating due to current).

    Smaller inverters (300 watt TSW) may consume around 6 watts of power (with nothing plugged into them). Larger inverters may consume around 10-20-60 watts just to run the electronics/transformer/etc. There are things that can be done to reduce power usage--Standby where nothing is switching until an external switch is turned on. Search Mode where the inverter turns on for 1 cycle every second looking for >6 watt loads. Or even only using 1/3rd or 1/2 the FETs when the loading is light.

    One thing that we talked about was the minimum AH rating of your battery bank to support your inverter... One simple rule of thumb is 100 AH @ 48 volts for every 1kW of Inverter rated output... In reality, if you are only planning on using 500 watts maximum for now, you could use a 50 AH @ 48 volt battery bank (just an example).

    Looking at your needs--You really need to specifiy what your power cycle is going to look like... Average Watts * 12 hour power failure, then how long you have to recharge the battery bank for the next cycle (i.e., you cannot use the inverter for 20 hours per day and recharge a near depleted battery bank in 4 hours for the next day's use).

    And battery types... AGM can supply or be recharged with very high current levels. GEL batteries can supply high output current but (usually) should only have a C/20 (5%) rate of charge to avoid damage. Flooded Cell should be operated at more conservative current levels--But are usually more forgiving of mistakes (as long as you keep the plates covered with electrolyte and don't take the battery "dead")...

    A lot of UPS applications use AGM or GEL batteries... Most Off Grid folks seem to use flooded cell lead acid batteries... Usually much cheaper than AGM. GEL are not usually recommended because of the low charging current and long charging time required to get back to full charge (i.e., 8 hours a day of sun/charging, 16 hours a day of load--Need something that can recharge quickly).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • techntrektechntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: ups as inverter - inverter electronics / again

    You can use flooded lead acid batteries with a UPS. Worst case the float voltage will be a little low, but some UPSs can be adjusted.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • fca1fca1 Solar Expert Posts: 124 ✭✭
    Re: ups as inverter - inverter electronics / again

    Hi understand, but once again my studer 2200 also have fets and transformers but it only uses 9w.
    Now the sua3000 ups is always consuming 2amps on top of the load, I mean if I have a load of 5amps the total amps going out of the batts are 7.
    I don't see what the type of bateries will change this because it consume the same with both my gel and agm banks ..
    It just seem a good replacement for a inverter, but this self consumption. Is a complete. No go for me..

    I Willl post some internal pics on what is inside ..
  • lancashire_hotpotlancashire_hotpot Registered Users Posts: 2
    The reason for the 2 amp load is because those transformers are massive lumps and its an APC UPS not an "inverter" per say. What that means is say if you are running the UPS as an inverter the APC unit doesn't know this and carries on looking for AC input voltage all the time, because that's its main job a UPS. That's quite some work to do, think about it constantly measuring the voltage every 50ms the voltage, voltage stability, wave distortion etc... etc... That APC UPS unit could be used to power anything. They output some of the cleanest power BUT!!!

    A good quality 48v sine wave inverter has idle features like someone explained above, so when the load is small it diverts the load to say 1/4 of the available mosfets on the board to save power consumption. Would love it if someone hacked the APC unit to have to extra features. I've got the SUA1500 @ 24v hooked up at home and its a dream. So going to get the SUA3000 and hook it up to 830ah forklift battery @ 48v with an FM60 Outback MPPT charge controller and have this as a supplementary circuit throughout the garage and home but only turn it on when I know I am going to be powering high loads. The sua1500 might be used for the fridge/internet satellite/TV or it might be more efficient to get a small 1000w inverter with an idle function connected to say 500ah.... Decisions decisions.... Thing is I love being able to have the geeky features of the APC units like monitoring the ac/dv voltage on a graph, estimated % of power left etc...

    What would you guys recommend?
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