Pure Sine-wave Inverter at an affordable price : Does it exist?

[Andy_GParticipant @andy_g]

Here you are:

Both of the above are with a 60W load on the inverter. The no-load waveforms are the same.

 

The multimeter is reading the output voltage of the inverter. (Don’t read anything into the X calibration on the scope as I had to turn the gain down on the X axis to fit the waveform on the screen.)

Photographing the scope was trickier than expected, but the biggest challenge was finding something with an incandescent lamp in to act as a load.

Switching things on and off etc:

I was impressed by the cleanliness of the waveform and the lack of transients on startup / load changes.

I hope that’s of some use.

 

Andy

[Robert Atkinson 2Participant @robertatkinson2]

As you know a “pure-sinewave” inverter in modern parlance menas a PWM inverter. Not really a sinewave but close enough. “modified sinewave” would be better called modified squarewave. These typically use two steps per half cycle. Better than a squarewave but not great for some applications. Both neeed careful design and filtering to meet EMC requirements. Cheap ones don’t have this. Victron are excellent, I’ve used them professionally but they are not cheap.

Depending on application you may not even need AC. Most modern electronic equipment uses switch mode powersupplies. The fist thing these do is turn the AC into DC. These supplies and equipment will run fine of about 300V DC. Non speed controlled brushed motors (drills etc) will also run fine on DC.

Robert.

[Andy_G]

On Andy_G Said:

I second Victron.

The 12/240 is the smallest one they do (240 VA for £83):

https://www.12voltplanet.co.uk/victron-phoenix-pure-sine-wave-inverter-12v-250w-vedirect-enabled.html

We have the 12/375 in the camper van for laptop charging, etc. (375 VA for £107)

https://www.12voltplanet.co.uk/victron-phoenix-pure-sine-wave-inverter-12v-375w.html

It is incredibly well made and surprisingly heavy (I think it has a real transformer inside). There is absolutely no trace of radio interference or electrical noise.

The very first time that you connect it to a battery there is a large current surge, but it can be left connected to 12V and switched on and off using a low current ‘remote’ switch.

I could probably get a scope trace if you were interested.

Oops missed this one.
As I said previously I’ve used Victron Inverters. Yes they are heavy. You are correct, this is because they do have “real” iron cored transformers. Toriodials to be precise.
Having investigated (taken apart) a couple I was surprised to find that they don’t use the usual architecture of  LV DC in, high frequency AC inverter with ferrite transformer, rectifier and filtering to HV DC, PWM HV DC to 50Hz AC with a bit of filtering.
The Victrons I’ve seen take LV DC, PWM swith it to a iron core toroid that steps up to mains voltage and some filtering on the output.
For the units that also charge batteries from the mains the same transformer is used to step down the voltage for the charging circuit.
At first it looks “old fashioned” but it works well and has good very good EMC and overload performance.

Robert.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the endorsement, Robert … Looks like we’re onto a winner.

MichaelG.

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Just to be clear, I only want a modestly powerful unit but the waveform quality is important to me … so the bottom-end of the Victron range is looking good.

Edit: __ I think my only concern is that they are clearly designed to be in a fixed installation, whereas I would prefer something that could be carried in the boot of the car and plugged into an Accessory Socket as and when required.

[Andy_G]

On Andy_G Said:

Here you are:

Both of the above are with a 60W load on the inverter. The no-load waveforms are the same.

 

The multimeter is reading the output voltage of the inverter. (Don’t read anything into the X calibration on the scope as I had to turn the gain down on the X axis to fit the waveform on the screen.)

Photographing the scope was trickier than expected, but the biggest challenge was finding something with an incandescent lamp in to act as a load.

Switching things on and off etc:

I was impressed by the cleanliness of the waveform and the lack of transients on startup / load changes.

I hope that’s of some use.

 

Andy

Excellent, thank you Andy

Grateful if you could provide a link to the [presumed] video though … as I am still unable to see embedded videos.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

[quote]

Switching things on and off etc:

I was impressed by the cleanliness of the waveform and the lack of transients on startup / load changes.

[Michael Gilligan]

On Michael Gilligan Said:

Thanks for the endorsement, Robert … Looks like we’re onto a winner.

MichaelG.

.

Just to be clear, I only want a modestly powerful unit but the waveform quality is important to me … so the bottom-end of the Victron range is looking good.

Edit: __ I think my only concern is that they are clearly designed to be in a fixed installation, whereas I would prefer something that could be carried in the boot of the car and plugged into an Accessory Socket as and when required.

They are fine for mobile and marine use but you are correct they are nomally fixed in place. Mount it on a bit of marine ply with a suitable DC input connector, output power strip and a couple of handles.
For DC power connectors I suggest Anderson “Power-Pole” types. These are available from 15A to hundread of amps. A “battery isolator” sold for boat and motorsport make a nice DC power switch.

Robert.

[Michael Gilligan]

On Michael Gilligan Said:

Grateful if you could provide a link to the [presumed] video though … as I am still unable to see embedded videos.

No problem.

The video has disappeared for me too now. I swear it was there!

Link to Youtube

(I’d save your popcorn for something else though 😉 )

[Michael GilliganParticipant @michaelgilligan61133]

Looks as good as one could possibly hope for !

Thanks again

MichaelG.

[noel shelleyParticipant @noelshelley55608]

Hi Michael, 2 things to watch, first is be aware that some units will not like being switched on with the load applied, always switch on the DC before connecting the load, second is that the 12v or24v supply will draw quite a hefty current so the DC side does need stout wire and good connectors. Noel

[Andy_G]

On Andy_G Said:

On Michael Gilligan Said:

Grateful if you could provide a link to the [presumed] video though … as I am still unable to see embedded videos.

No problem.

The video has disappeared for me too now. I swear it was there!

Link to Youtube

(I’d save your popcorn for something else though 😉 )

This happened to me a couple of days ago on this thread too; I embedded a video, which I’d forgotten Michael wouldn’t be able to view on an iPad.
I then went back and the whole post had gone completely for me, not just the video.
Someone else then showed a shot of my own post that I couldn’t see myself; I then forced an F5 refresh and my own post became visible again.

Bill

[Michael GilliganParticipant @michaelgilligan61133]

Bullet bitten 🙂

I have ordered the little Victron inverter from:

https://www.12voltplanet.co.uk/victron-phoenix-pure-sine-wave-inverter-12v-250w-vedirect-enabled.html

as per Andy’s advice.

MichaelG.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

[…] Mount it on a bit of marine ply with […]

Saved myself a bit of tedious woodwork today

A visit to HomeBargains produced a pale grey plastic chopping board, a little larger than A4 … upon which the Inverter will sit very nicely.

At £1.99 a pop, a real bargain I would say.

[travel expenses, of course, need to be written-off elsewhere]

MichaelG.

.

[Mark RandParticipant @markrand96270]

Any inverter can produce a ‘pure sine wave’ with an LC filter on its output. That’s what I do for the shed’s three phase supply 🙂

 

https://www.reo.co.uk/types/filters/sinusoidal-filters/

https://inverterdrive.com/group/Sine-Filters/

[Mark Rand]

On Mark Rand Said:

Any inverter can produce a ‘pure sine wave’ with an LC filter on its output. That’s what I do for the shed’s three phase supply 🙂

 

https://www.reo.co.uk/types/filters/sinusoidal-filters/

https://inverterdrive.com/group/Sine-Filters/

But those cost much more than the qualty inverter the OP just bought…….
Even then they would not work well with the two step “modified sinewave” invertrs as they are designed to work with multi kHz PWM motor drive outputs not two step inverters.

Robert.

[Mark RandParticipant @markrand96270]

Sigh…

They were an example of the breed. One can roll one’s own for trivial expense.

I cannot recall seeing a non-pwm inverter in the last few decades. The last application I saw for one was starting the 300MW hydro generators at Dinorwig in pump mode

[Robert Atkinson 2Participant @robertatkinson2]

Hi Mark,

I think you have not understood the OP’s requirement. He is not talking about a motor drive 3 pahse inverter (VFD) but a 12V to 240V 50Hz inverter to run mains equipment from a car battery. The vast majority of these, include many of those advertised as “pure sinewave” don’t use PWN on the 50Hz output Those with a high frequency step up section may use PWM on that but not to produce a sinewave. They use a two step “modified sinewave” which is not suitable for all loads.

Building a 50Hz power sinewave shaping filter even for a few hundred watts is not trival in either design or cost of components. if you know of a low cost design please sare it and the source for components.

Robert.

 

 

[SteviegtrParticipant @steviegtr]

Michael why do you need pure sine wave. Brother in law on his 5th camper build always uses the el cheapo’s. He runs a tv, laptop, fridge + more & all seem to run perfectly well.

Or is it for something special.

Steve.

[Michael GilliganParticipant @michaelgilligan61133]

Possibly unnecessary, Steve … I may never know [or care] … I just felt the need to use pure sine-wave on the power supply for a Medical monitor that I may need to take out in the car; and one thing led to another.

It’s really not worth delving into the reasoning …  Thanks to wise advice from forum members, I now have what I wanted, at a price I was willing to pay.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Following Robert’s excellent appreciation of my requirements [which are now nicely met] I am very happy for this discussion to be broadened to include other options that may better suit other needs.

MichaelG.

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