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Battery powered 230VAC Inverter, safety precautions?

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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Folderol » Thu Dec 19, 2019 4:54 pm

Sam Spoons wrote:
Sam Spoons wrote:Might still change it just to get rid of the buzz. Found this on Amazon but it looks too good to be true at that price, what do you think?

https://www.amazon.co.uk/Almencla-Power-Inverter-AC220V-Ports/dp/B07V63S3BC/ref=sr_1_13?keywords=pure+sine+wave+inverter&qid=1576239800&s=electronics&sr=1-13

Not sure about that one but I bought this one off ebay https://www.ebay.co.uk/itm/300W-Power-Inverter-Charger-12V-DC-To-AC-230V-Converter-Car-Pure-Sine-Wave-USB/293221255983?hash=item4445594b2f:g:5I8AAOSw0lVdd7Ph

And despite being listed as a "pure sine wave'" inverter the docs enclosed say it is a "modified sine wave" inverter so that's going back without ever being plugged in.

Presumably marked as:
Not as described. Unfit for purpose.

I sometimes wonder whether these people are just shysters or simply have no idea at all about what they have.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby blinddrew » Thu Dec 19, 2019 5:39 pm

Little bit of column A, little bit of column B...
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Sam Spoons » Thu Dec 19, 2019 6:07 pm

Folderol wrote:Presumably marked as:
Not as described. Unfit for purpose.

I sometimes wonder whether these people are just shysters or simply have no idea at all about what they have.

Yup, that's about it, I won't be paying the return carriage either.....
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby merlyn » Fri Dec 20, 2019 4:41 pm

And despite being listed as a "pure sine wave'" inverter the docs enclosed say it is a "modified sine wave" inverter so that's going back without ever being plugged in.

Sorry to hear that. I'm kind of shocked that it was the pure sine wave bit they were lying about.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Sam Spoons » Fri Dec 20, 2019 5:23 pm

It did sound a little too good to be true :roll:
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby wireman » Sat Jan 04, 2020 6:09 pm

A long time ago in this thread I said I would try to get a trace from my UPS which I have now done. Didn't want to rush in connecting my scope to 240V!

This is the trace when the UPS is on mains power...

Image

This is the trace when the UPS is on Battery power (16% loaded).

Image

The UPS is set to output 230V but keep within the range 207V-253V, my normal mains voltage is around 245V

Although I'm happy to see the on-battery waveform I'm a bit surprised with the peaks of the other one and wonder if the UPS is trying to clamp the voltage even though the settings should not make it do that. Unfortunately I forgot to get a trace of the mains input to the UPS.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Sam Spoons » Sat Jan 04, 2020 6:26 pm

How did you safely connect the scope to the UPS' mains output?

I have finally had resolution for the dodgy 'modified sine wave' PowerPack. Amazon are refunding me in full as "item not received". I have exchanged numerous emails with the seller who was happy to accept the return but could not send me a return lable unless I did the return request through Amazon's system. But, Amazon's system said the power pack was 'not eligible for return' as it contained batteries :headbang: I tried three different carriers all of whom refused to carry the power pack 'cos it contains batteries :headbang: so the seller asked me to send a short video of the issue and said, on receipt, they would refund me without the need for me to return the item.... but..... Amazon would not send the video through their email filtering system so the seller did not get it. The seller asked me to send it to their, attached, email address..... but 'zon's filters stripped the attachment from the message........

Eventually (8 emails to the seller and 8 replies later) I contacted Amazon for a second time, who said they would contact the seller, upon which I said the seller had been attempting to resolve the issue but Amazon's email filters kept removing relevant information......

Then later that same day I received an email from Amazon saying they had decided the case in my favour and would be actioning a full refund. I'm just waiting for that to hit my bank account. A bit of a mission but I'm sure I'll find a use for my freebie power supply even if it's just as a phone charger in the campervan.......
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby wireman » Sat Jan 04, 2020 6:53 pm

Sam Spoons wrote:How did you safely connect the scope to the UPS' mains output?

One UPS output goes to a 13A extension strip (speakers, lamp, interface).
So I used...

Image

and a Micsig probe...

http://www.micsig.com/html/41.html
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Hugh Robjohns » Sat Jan 04, 2020 7:08 pm

wireman wrote:The UPS is set to output 230V but keep within the range 207V-253V, my normal mains voltage is around 245V

245 is a high incoming mains voltage. Are you very close to a substation transformer by any chance? Did your old incandescent bulbs blow fairly often? :lol:

If it's an APC UPS, I think the range (207-253) value sets the acceptable incoming mains voltages that it will pass through to the connected load devices without intervention. Or in other words, the incoming mains supply voltage needs to fall below 207 or rise above 253 before it switches over to the battery/inverter supply.

Although I'm happy to see the on-battery waveform I'm a bit surprised with the peaks of the other one and wonder if the UPS is trying to clamp the voltage even though the settings should not make it do that.

Not quite sure what your concern is. The voltage of the incoming mains ( nominally 230V) is an RMS value. So the peak-to-peak voltage will be around 650V (or +/-325V). If your incoming is 245Vrms then the p-p value will be around 692 or +/-346V on the scope trace.

If your concern is the flat-topping on the raw mains supply, that will be distortion caused by local loads drawing power from the supply -- loads in adjacent buildings and streets as well as those in your own building.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Wonks » Sat Jan 04, 2020 7:13 pm

I think he means the peaks of the mains-on sine wave look a bit flattened and ragged. However it would be nice to know what the incoming mains to the UPS looked like, to see if it was the same or smoother.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby merlyn » Sat Jan 04, 2020 7:42 pm

I would think the shape would be exactly the same coming straight out the wall. What you posted looks pretty good for a mains supply. You may find the shape changes throughout the day as the load goes up and down, the purest sine wave being in the middle of the night when the load is at a minimum.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby wireman » Sat Jan 04, 2020 7:57 pm

I'll try to do another comparison next weekend and it was the apparent roundoff I was interested in.
UPS is APC Smart UPS SMT1000i and I was certainly expecting a sine wave from a device in that category.

Yes voltage has always been high, nearest connection point to the pylons is probably around 1km away.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Hugh Robjohns » Sat Jan 04, 2020 8:29 pm

wireman wrote:... it was the apparent roundoff I was interested in.

Ah, okay. As has been said, it's due to network loading and it will undoubtedly vary throughout the day. That's actually a pretty good waveform -- I've seen much, much worse.

UPS is APC Smart UPS SMT1000i and I was certainly expecting a sine wave from a device in that category.

Yes, I'm a fan of the Smart UPS boxes, they are very good.

...voltage has always been high...

It would be worthwhile contacting your electricity supplier and discussing it with them. It is within tolerance -- the current spec is 230V -6% /+10% which means 216 to 253.0 Volts. But at 245V it is most definitely on the high side and it will be stressing your home equipment unnecessarily.

The step-down transformers from the grid have output taps to allow the local supply voltage to be adjusted. It may be that yours hasn't been changed since the EU harmonisation...
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Sam Spoons » Sat Jan 04, 2020 9:31 pm

I don't monitor the mains voltage in my audio constantly but it's usually 230V or higher, I have the monitor plugged in at the moment as I've been checking the power draw of the AER ,* I've just had a quick look and it 240V just now but I'm sure I've seen 245+ over the last couple of days.

* All about this power pack above.......
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