Cool tutorial: Converting an APC UPS into a powerful sinewave inverter

[BradC]

Hi the problem is; I d'nt have the that board to connect to my computer,to change configuration, i have the RJ jack. I tried to connect, but when i connect the cable, the ups gos off i'm not sure if can use the software without that pc card.

If you don't have the specific APC cable, then that is normal behaviour. They mangle pinouts such that if you plug a normal serial cable in it shuts down the UPS. Yay.

What about to change the dc imput from 48to 24dc?

Forget it. There's another thread here somewhere where the originator wanted to do that, and when the magnitude of the changes required was explained he very quickly decided against it.
You've got the voltage/current sensing dividers, the logic power SMPS, the H Bridge driver, the transformer configuration and then you'll halve your power handling capacity.

There's a reason the 1500 is the largest 24V unit.

[NJM]

Thanks anyway, I  am  tryng to put  on the smart3000 box, one power inverter 24dc to 110ac and another ups pure sine wave 24 to 230ac pure sine wave made in Italy it uses 2 toroidal transformers,i have a plan to use it on my beach house, doing some kind rondon use of the 3 componnents.i raised the original box , put heatsink for the transformers, and tryng some improvements for the intire system.Thanks.

[johansen]

There are two interlinked asics. The first manages the charging and mains phase comparison, the second manages the PWM. They don't have any internal power smarts and receive their sine wave reference from a DAC connected to the main CPU. The CPU generates the sine wave reference, and slews it over 4 seconds to ensure it's in sync before they switch back to mains. Aside from the funky boost charging, pretty much all the smarts in these units is in firmware. It also changes the inverter frequency depending on the incoming mains. It'd be interesting to compare that generated sine to see if there is a DC offset in there relative to what hits the H-Bridge.

well, it regulates the output voltage as well, i'm not sure if that's handled by the asic or the cpu. the frequency is variable as you note. however, there are a few ways to change it. one is to insert an inductor in the transformer, which lowers parasitic loss. it also reduces the switching frequency. the other method is to change the filter capacitor on the output. usually its 10-20uF depending on the model. you can drop it as low as 3uF it will probably still work. i also tried changing the current transformer ratio by looping the capacitor through it several times, but this did not have nearly as much effect on switching frequency as i thought it should have. so why an inductor in series with the tx can case such variation, i don't know.

[mbr89]

http://www.ti.com/lit/an/slaa602a/slaa602a.pdf

2) Mains Mode:

In the mains mode, both the high-side MOSFETs ie A side as well B side is switched off and both the low-side MOSFETs are switched with the similar PWM waveform where the duty cycle of lower side PWM signals determine the charging current.



When the lower switches are turned on at the same time, there is a boosted voltage, that appear across the primary leakage inductance of transformer connected to the H–Bridge, by the Ldi/dt effect and this energy is use to charge the battery through the body diodes of the high-side MOSFETs. Also each of the high-side MOSFET’s body diode will conduct in the each half of the Sine Wave.

When the mains mode is sensed, firstly all the MOSFETs are switched off and the Relay between the Ac input and the Inverter output is connected. After this, the Lower FETs are tuned on with PWM of small duty Cycle (5 to 10 percent) and the high-side MOSFETS are switched off. Now the voltage across the current sense is measured by controller and if the corresponding current is less or more than required by charging algorithm than the duty cycle is altered correspondingly ie duty cycle is increased if more charging current is required and decreased if the charging current reduction is desired.



Figure 30. Waveform During the Charging Mode. The High-Side FET is Switched Off and Both Lower-Side FETs to Ground in the H Bridge are Switched at the Same Time With the Duty Cycle Proportional to the Battery Charge Current

I think the maximum charging current is not a question of how many MOSFETs you put in....

https://en.wikipedia.org/wiki/Power_MOSFET#Body_diode

... they can handle large currents and ...

[crazy_driver]

hi guys, i've been searching about a problem with apc ups that go in overload even with no load and that get solved by just remplacing a few caps.
Do any of you know witch ones should i switch on this topic's model?

[BaronVonChickenPants]

I have been looking at an APC 3000VA and 7500VA 240V SmartUPS's and have notice that the inverter output has a floating neutral. When either UPS is in bypass mode running from mains they have the normal MNE readings but when the output is coming from the batteries or if the 7500VA is set the full double conversion mode the neutral measures between 90-120 volts to earth and the active is 160-120 volts to earth. With no load the neutral reads about 90 and active 150 but the balance out to 120 each way once there is a load.

I believe this is due to the way the inverter circuit works where the +48v DC from the battery is connected as 0v AC and the the battery DC negative is flicked between the high and low to give 96V AC which is then fed through smoothing circuit, transformers, etc.

Should the inverter output have a neutral earth bond, I fear this would likely the damage the inverter.

Interested to hear other thoughts on this.

Regards,
Jordan

[Bratster]

I have been looking at an APC 3000VA and 7500VA 240V SmartUPS's and have notice that the inverter output has a floating neutral. When either UPS is in bypass mode running from mains they have the normal MNE readings but when the output is coming from the batteries or if the 7500VA is set the full double conversion mode the neutral measures between 90-120 volts to earth and the active is 160-120 volts to earth. With no load the neutral reads about 90 and active 150 but the balance out to 120 each way once there is a load.

I believe this is due to the way the inverter circuit works where the +48v DC from the battery is connected as 0v AC and the the battery DC negative is flicked between the high and low to give 96V AC which is then fed through smoothing circuit, transformers, etc.

Should the inverter output have a neutral earth bond, I fear this would likely the damage the inverter.

Interested to hear other thoughts on this.

Regards,
Jordan

I have no direct experience with APC UPS' of that size.

But on the couple of UPS's that I have wired up in that size range they have been terminal strip for the connections.

And depending on what output voltage you want (straight 120 volts, 120v/240 split phase, 240 or 208) you can connect things to different terminals. One of the options is if you want a neutral to ground Bond.

 Depending on which output voltage configuration you use the neutral to ground Bond would need to be on different connections so it could be left out from the factory.

Again this is all just my past experience with UPS is in that range. I have no idea what UPS you have. Take all of this with a grain of salt.

I would consult the manual for your ups and see what options it lists.

Sent from my Nexus 6 using Tapatalk

[mbriaz10]

Hi cte4ds

First of all thanks for this wonderful tutorial. I really enjoyed the mod and feedback provided by the community. I have recently bought rundown APC3000SU and APC3000XL versions and have already mod these with additional mosfets and the watt capacity is increased. one of these units is always running on batteries 24*7 at an average load of 5-10A @ 220V without any issues. The other one is there for standby in case needed. Now i have realised that due to weather changes my power consumption is de-creased and wanted to grid tie my solar setup so can sell additional power to grid which i would like to buy back in summer. Was wondering if I can mod these UPS's to grid tie inverters with your following idea.
Also if these UPS can be parallelly connected to each other in 220 AC output provided if I mod these to synch with main somehow?

Thanks

Solar Setup
5000W Solar Array-Outback FM80 - Narada 800X 24* 2V - APC3000SU/APC3000XL
2500W Solar Array-Outback FM60 - Narada 800X 24* 2V - APC3000SU/APC3000XL


"
One thought I had is if these units could be turned in to grid-tie inverters, because from what I understand the inverter on these things is always running in sync with the AC mains input, so it might be as easy as modifying the output of the inverter in parallel with mains input and connecting your solar or wind power to the battery input. Not that I wanted to do that but just a thought
"

[nokos]

Hi everyone.

Could you tell me where I can tap 24 V or 12 V from an internal power rail in an APC SUA1500I? I need it to power an external fan controller.

Thanks

[johansen]

Hi everyone.

Could you tell me where I can tap 24 V or 12 V from an internal power rail in an APC SUA1500I? I need it to power an external fan controller.

Thanks

you can get 26vdc from the battery.

its unlikely you can find 12v with enough margin to run a fan.

[nokos]

I know, but I’m looking for a switched 12 V or 24 V rail. I’d like the fan controller to turn on with the UPS when I press the power button and turn off when the UPS is shut down.

[BradC]

You'd be better off just tapping the power led and using that as a logic signal to switch the 24V rail off the batteries.

[nokos]

Thanks. I understand what you mean about using the power LED as a logic signal.

I’d still prefer to find an existing switched supply point on the SUA1500I PCB and power my fan controller directly from there, but I’m not sure where to look.

The controller should draw no more than about 0.8 A. The existing fan supply would also be perfectly fine if it can provide the extra current and is only active when the UPS is switched on.

Do you know where on the SUA1500I PCB I could find a suitable switched 12 V, 24 V, or fan-supply point to tap into?

[BradC]

Thanks. I understand what you mean about using the power LED as a logic signal.

I’d still prefer to find an existing switched supply point on the SUA1500I PCB and power my fan controller directly from there, but I’m not sure where to look.

The controller should draw no more than about 0.8 A. The existing fan supply would also be perfectly fine if it can provide the extra current and is only active when the UPS is switched on.

Do you know where on the SUA1500I PCB I could find a suitable switched 12 V, 24 V, or fan-supply point to tap into?

If I did I wouldn't have made the suggestion of the power led. I combed several schematics, and suggested the most viable reliable way of doing it.

As soon as a battery is plugged in and power button pressed the first time the UPS powers up. The power remains on until the UPS is forcibly powered down (disconnected from the mains and hold the power button down until it shuts off). So you can turn the load on and off as much as you like but the UPS power rails all remain powered until you force it off (search SmartUPS brain dead for the procedure). The power led follows the soft power state.

The fan on an SUA is PWM controlled and the algorithm varies depending on the model and firmware version. Most run slowly full time then ramp up while on battery or charging. That won't do what you want it to do.

The old SU series only switched the fan on when on battery or charging so they were silent(ish) mostly. I modified mine with a resistor across the switch fet so the fan runs all the time slowly.

[nokos]

Thanks, that makes sense.

The problem I see with using the LEDs as the control signal is that I really need one signal that means “UPS ON”, regardless of whether the load is being supplied from mains or from the battery.

On this SUA1500I front panel, the indication changes depending on operating mode — for example “On Line” is lit when running from mains, while “On Battery” is lit when the inverter is supplying the load.

So using only one of those LEDs would not reliably represent the overall UPS ON state.

Do you know if there is another point in the UPS where I could pick up a clean logic signal that simply indicates that the UPS output is enabled / the unit is in the ON state, independent of whether it is currently running from mains or battery?

I only need it as a logic signal to drive the EN input of my DC-DC converter, not as a power source.