Author Topic: Cool tutorial: Converting an APC UPS into a powerful sinewave inverter  (Read 83873 times)

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Online BradC

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Re: Cool tutorial: Converting an APC UPS into a powerful sinewave inverter
« Reply #50 on: April 06, 2017, 07:56:56 am »
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.

 

Offline NJM

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Re: Cool tutorial: Converting an APC UPS into a powerful sinewave inverter
« Reply #51 on: April 06, 2017, 11:48:28 am »
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.
 

Offline johansen

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Re: Cool tutorial: Converting an APC UPS into a powerful sinewave inverter
« Reply #52 on: April 06, 2017, 11:17:57 pm »
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.
 

Offline mbr89

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Re: Cool tutorial: Converting an APC UPS into a powerful sinewave inverter
« Reply #53 on: August 20, 2017, 03:53:41 pm »
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 ...
« Last Edit: August 20, 2017, 04:19:28 pm by mbr89 »
 

Offline crazy_driver

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Re: Cool tutorial: Converting an APC UPS into a powerful sinewave inverter
« Reply #54 on: October 13, 2017, 09:06:30 pm »
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?

 

Offline BaronVonChickenPants

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Re: Cool tutorial: Converting an APC UPS into a powerful sinewave inverter
« Reply #55 on: December 02, 2017, 11:05:36 am »
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
 

Offline Bratster

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Re: Cool tutorial: Converting an APC UPS into a powerful sinewave inverter
« Reply #56 on: December 02, 2017, 07:41:30 pm »
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

 


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