Converting a modified sine wave to pure?

[Tim Good]

I have an integrated system in my boat where I just press a button to invert 240v to all sockets.

That’s fine but a modified sine wave won’t run an induction hob and I already have 240v cables running to the galley from the battery bank.

Rather than installing a new inverter at the batteries and leading a new cable etc, I asked ChatGPT if I could convert a modified wave to a pure wave. Response in below:

Now option 2 seems the most practical since I can use the existing cable but does anyone have experience with this?


Yes, it is possible to convert the AC electricity from a square wave (or modified sine wave) inverter into a pure sine wave. This can be done using a filter circuit or an additional pure sine wave inverter module. Here are some approaches:

1. Low-Pass Filter

• How It Works: A low-pass filter smooths out the sharp transitions in the square wave output, producing a waveform closer to a pure sine wave.


• Components Needed:
• Inductors (chokes)
• Capacitors

Design Considerations:

• The filter must be designed for the frequency of the inverter output (typically 50 Hz or 60 Hz).

• Proper sizing of components is crucial to avoid overheating or inefficiency.


Challenges:

• A simple low-pass filter may not completely eliminate higher harmonics, leading to a waveform that is not perfectly pure.
• Power losses can occur, especially with high loads.

2. Using a Pure Sine Wave Inverter Module


• How It Works: Pass the square wave inverter’s output through a pure sine wave inverter. The module will rectify the incoming waveform into DC and then convert it to a clean sine wave AC.

Advantages:
• Produces a true pure sine wave output.
• Handles a wide range of loads and is easier to implement than designing a filter circuit.

Challenges:

• Requires an additional investment in the module
• Efficiency is slightly reduced due to the extra conversion step.

 

[DrSpock]

Your mistake was asking ChatGPT. The simplest option is to buy a pure sine wave inverter and sell the old one.

 

[AntarcticPilot]

Any of those solutions will result in inefficiencies. Filtering a square wave, for example, will lose at least half the power; a "modified sine wave" will also lose substantial amounts, though not as much as a square wave. Your filter circuit would probably double as a nice heater!

 

[PaulRainbow]

I have an integrated system in my boat where I just press a button to invert 240v to all sockets.

That’s fine but a modified sine wave won’t run an induction hob and I already have 240v cables running to the galley from the battery bank.


Rather than installing a new inverter at the batteries and leading a new cable etc, I asked ChatGPT if I could convert a modified wave to a pure wave. Response in below:

<snip>

If you already have cables running from the battery bank to the galley it's a simple swap, surely ?

I have a 3kw pure sine wave inverter/charger in the for sale section if you're interested, it is 24v though.

 

[Tim Good]

Your mistake was asking ChatGPT. The simplest option is to buy a pure sine wave inverter and sell the old one.

I wouldn’t be hear asking if it was that simple.

My existing inverter is built into a charger and shore power system. All routed via various points of management etc.

I only need a pure sine wave for a single appliance in the galley

 

[Tim Good]

If you already have cables running from the battery bank to the galley it's a simple swap, surely ?

I have a 3kw pure sine wave inverter/charger in the for sale section if you're interested, it is 24v though.

It’s not that straightforward. My inverter / charger (Heart system) is on the starboard side. Batteries also. Then my electric panel with the 240v system (switches and breakers) is all on port, where the 240v galley cable goes from. I can’t locate an inverter there without running a very substantial 12v supply,

 

[westernman]

If you already have cables running from the battery bank to the galley it's a simple swap, surely ?

I have a 3kw pure sine wave inverter/charger in the for sale section if you're interested, it is 24v though.

I had a "pure" sine wave inverter which I used for charging our electric tooth brushes. These use a small contactless inductive charger.
The "pure" inverter killed these charges off on a very basis. At home they never failed. On the boat they would not last more than a week when anchoring.

I.e. there seem to be various qualities of "pure". (I am risking getting banned for religious discussion now....)

 

[Tim Good]

I had a "pure" sine wave inverter which I used for charging our electric tooth brushes. These use a small contactless inductive charger.
The "pure" inverter killed these charges off on a very basis. At home they never failed. On the boat they would not last more than a week when anchoring.

I.e. there seem to be various qualities of "pure". (I am risking getting banned for religious discussion now....)

You know you guy buy usb and 12v powered electric toothbrush chargers right? Cost us about £3 on eBay and going strong 7 years later.

Same with laptop chargers. They all have a 12v version.

 

[PaulRainbow]

It’s not that straightforward. My inverter / charger (Heart system) is on the starboard side. Batteries also. Then my electric panel with the 240v system (switches and breakers) is all on port, where the 240v galley cable goes from. I can’t locate an inverter there without running a very substantial 12v supply,

I'm clearly missing something here......

If the existing inverter and batteries are both on port side and the distribution panel is on Stb side, why can't you just replace the existing inverter/charger with a sine wave inverter charger and use all of the existing wiring ?

 

[ylop]

I'm clearly missing something here......

If the existing inverter and batteries are both on port side and the distribution panel is on Stb side, why can't you just replace the existing inverter/charger with a sine wave inverter charger and use all of the existing wiring ?

It does seem like the logical solution. Almost like actual intelligence is able to understand the context of the question (such as provided to it) and come to a practical solution whilst artificial intelligence has no understanding of context or even actually the meaning of the words and so produces stuff like this:

• How It Works: Pass the square wave inverter’s output through a pure sine wave inverter. The module will rectify the incoming waveform into DC and then convert it to a clean sine wave AC.

can you and should you are not the same thing.

 

[Baggywrinkle]

If you are an electronic hobbyist and understand how an inverter works, and if you can identify all the components required, and can modify your existing device, then it can be done in theory.

Here is an example ....

As the YouTuber summarised .... "The process involves increasing the output voltage of the transformer, increasing the switching frequency of the output MOSFETs, feeding an sPWM signal to the gates of the output MOSFETs, using a low-pass filter to convert the sPWM to pure sine wave, and using a feedback loop to stabilize the output voltage."

If you feel up to it then fill your boots

 

[Baggywrinkle]

As an aside, all this AI hype is currently following the well-proven Gartner hype cycle, this particular answer from ChatGPT is, in my humble opinion, a great example of the "trough of disillusionment" ....



... I don't know exactly how much context ChatGPT was given, or how the question was phrased, but the answer is a very typical, and pretty useless, bland summary with no real, applicable content.

This is a reasonable summary of how to ask AI questions ....

Expert Tips on How to Ask AI Questions Strategically | Atlassian

 

[William_H]

I had a "pure" sine wave inverter which I used for charging our electric tooth brushes. These use a small contactless inductive charger.
The "pure" inverter killed these charges off on a very basis. At home they never failed. On the boat they would not last more than a week when anchoring.

I.e. there seem to be various qualities of "pure". (I am risking getting banned for religious discussion now....)

I would suggest that your "pure sine wave" is not pure. get someone witha portable osciloscope to examine the produced wave form.
A sine wave inverter constructs the sine wave from a series of pulses of high but varying voltages perhaps 100 times per AC cycle. This construction is fairly easily smoothed with a capacitor to produce a pretty close to sine wave. As opposed to a "modified sine wave " which has perhaps one or 2 steps to construct the AC wave so lots of harmonics in what is produced too hard to filter.
Which gets back to ChatGPT whose answer being a filter is correct but only practical for very low power cases. For your many hundreds of watts for an induction stove filter capacitors and inductors would be physically very large and expensive. I have never heard of it done in power supplies. The alternative from ChatGPT would work but again involves an additional stage of power conversion each with losses. I recall an article in I think "Wireless World" UK publication must have been 50 years ago discussing design of filters for just this application. Not practical now compared to modern digital switch technology.
The only option for powering the induction stove from battery supply is another inverter. Either replacing existing one or stand alone just for stove. Do fit the inverter near the battery with short stout supply leads with perhaps a relay to power it up straight from battery via large fuse. Then 240 wiring across to stove.
ol'will

 

[arcot]

Using 6 kw lithium iron at 12 volts and a 2500 Watt sine wave inverter with an induction cooktop....
.
battery gauge jumps around from 12 volts to 14 making voltage unreadable while using induction cooktop.
.
Probably due to lack of averaging in voltage sampling.
.
Victron smart shunt may average voltage readings and allow accurate readings.

 

[PaulRainbow]

Using 6 kw lithium iron at 12 volts and a 2500 Watt sine wave inverter with an induction cooktop....
.
battery gauge jumps around from 12 volts to 14 making voltage unreadable while using induction cooktop.
.
Probably due to lack of averaging in voltage sampling.
.
Victron smart shunt may average voltage readings and allow accurate readings.

What make/model of inverter ?

6kw Lithium ?? That doesn't make any sense.