What will work with modified wave form?

[ericmark]

We have pure sine wave and modified sine wave and most household appliances will work with either. However it seems some will not. How before buying can one work out what will and what will not run with a modified sine wave?

On a boat because of the problems with catholic protection it is common to have an isolating transformer. I would expect if the output from an inverter giving out a modified sine wave was feed either in parallel or through one of these to would modify the sine wave further getting it closer to the pure waveform would this be enough to allow equipment which will not run with modified sine wave to now work?

Some generators do not connect directly to the output but also go through an inverter so the motor speeds can vary with load so saving on fuel. Or be driven as an auxiliary again the engine speed can vary by output frequency will remain the same. There seems to be very little information as to wave form. Do these generators also have problems due to wave form not being true sine wave?

There are also inverters designed not as stand alone but as a “Grid tie inverter” and from solar panels and the like they feed the existing domestic supply and reduce the power taken from the main supply. Do these modify the sine wave and will these stop some items from working?

Looking at Inverter suppliers and Power-Tek generators they give very little information as to what will and what will not work on a modified sine wave. And walk into a shop selling freezers and ask will this freezer work on a modified sine wave and one is met with a blank expression and “What!!!!” or words to that effect.

So how does one work out what will and what will not work?

Modified Sine Wave

• ericmark
• 8 Dec 2009
• 3

is what a modified wave form looks like and

True sine wave

• ericmark
• 8 Dec 2009
• 2

is the wave form from inverter generator (They look like modified vehicle alternators) found two one South African the other Siemens (Travel Power 991 00 10-06 package). The latter downloaded PDF but lost site.

Considering my Son and daughter-in-law will want all items to run of modified sine wave I want to work out what we can get them.

 

[NotHimAgain]

First take a look at this:
http://www.cfmeu-construction-nsw.com.au/pdf/sabaninverters.pdf.

To answer your question - its most likely that electronic equipment may have some trouble with the harmonics in a distorted sine wave. So thats most appliances these days then .

Resistive loads such as heaters and incandescent filament lights should be ok.

I haven't checked, but would I be right in saying that your high powered inverter cost less than £ 200.00 - there is a reason why top of the range ones cost nearer £2000.00

I have a yacht (36' blue water capable) - I don't have all this trouble - when we are offshore we just give up washing .

 

[BS3036]

Sorry Eric, but I had to smile at the "catholic protection".

 

[bernardgreen]

Sorry Eric, but I had to smile at the "catholic protection".

These are condoms that the priest has blessed to make them holy....

 

[BS3036]

 

[wotan]

Catholic protection Cathodic

intentional error

Wotan

 

[jj4091]

Is that protection from catholics or by catholics , seriously though is this any help http://solar-panel-review.com/sine-wave-inverters/guide

 

[ericmark]

Spell checks rule KO. But apart from that thanks to "NotHimAgain" and the ban is interesting. I am surprised that electronic equipment has problems as most is powered through a switched mode supply so is turned into DC before use. Not had any problem with Laptop or anything which in the past I have powered from small 150W version. But the fridge would not start as although run under 150W start was well over. And my mothers mobility scooter would not charge if the battery was flattened over a limit seems it used a pulse charge method which again took more power than the little 150W version could supply. But my phone charger is often used from the inverter as never bothered getting car charger.

I am wondering what will happen when the microwave is plugged in this is a worry. Although they were listed together with TV's as things one could use with it.

The reference to florescent lights has me wondering though.

Attention:
Fluorescent Lamps:
When switching on fluorescent lamps or tubes the inductive tensions can develop some of thousand Volt.
Therefore, you must let insert a connecting starter.
Additional 230v Alternating Current Generator:
You need a special switching device that it comes no damage to the Power Inverter.
Cigarette Lighter Plug:
The plugs are made only for an output up to 200 Watt.
Please don’t use Inverter and Appliances which have a higher operating level.

What is a connecting starter? Not that it makes any difference all lights are 12vdc. Says no more than 10 meters of cable should be used to connect but nothing about how big the cable should be except to say over 200W don't use cig lighter socket. Nothing to say what size cable to use. I think I will use 266/0.30 doubled up so 2 x 135A? Mainly as cable is in stock.

I think we must check as to if it is connected to earth through battery but noted the earth connection on back so assume that means it's not connected to battery neg output.

Also considered if we can connect 13A plug to 16A socket to connect to boats power system. This will mean RCD in circuit and no way to connect to shore power without disconnecting inverter first. But not happy with single plug as inverters sockets are the multi-plug type and neither am I happy with doubling on plug in case one is unplugged. Don't want to open inverter. I will talk to son about it. If not too much power is used then single plug may be best. Or two circuits but then need second RCD.

The instructions are very poor. And although both my son and I are electricians so not a problem for us I can see others would have problems. Even little things like access to crimp pliers able to crimp 25mm lugs.

As you say cheap. But 9Kw UPS I set up in Falklands was not what one would consider well made and that cost a fortune. Bought because generators kept failing but by time it arrived problem was solved so unit caused more power failures to comms equipment than if it had never been fitted.

The main problem was fridge/freezer as to empty them before cruising or to take ashore is not really an option. And Winsford to Chester is not far so to take boat to Chester for night out is good idea. But everything would have de-frosted before they got back. 4MPH is not that fast.

 

[NotHimAgain]

There is nothing wrong with cheap provided you can live with its limitations.

I mentioned harmonics, and as you no doubt know, these will be present in any distorted wave. A square wave can be 'created' by adding together as many odd harmonics, increasing in frequency, as possible. This implies that a square wave can be said to contain odd harmonics.

These can pass through the power supply into electronic equipment if no steps are taken (low pass filtering) to prevent them. Whether this would cause problems would depend on the particular equipment.

The impedance of inductive loads such as motor windings will be higher as the higher harmonics increase the inductive reactance (Xl = 2 * PIE * f * L ohms).

On yachts operating offshore there could be serious problems if the high frequency waves manage to radiate interference (again I am sure you know this with your radio experience). This might cause navigation and communication systems to malfunction.

Finally, as with many small power sources, there are question marks over shock protection - take a look at section [551] in BS 7671.

These questions should be considered:
1) Will RCDs work (remember some have electronic amplifiers in the detection sensor).
2) Can the unit provide enough current to operate an mcb under fault conditions (many small generators cannot).

 

[BS3036]

You raise a serious problem, Eric. I am considering battery backup for my solar heating controller, so as to be able to prevent a stagnation event in the event of a mid-summer power failure. There have been suggestions published which suggest that my controller runs incorrectly from a modified sine wave.

However, I think you are talking about two separate issues:

- Will the inverter provide a sufficient startup current in excess of its rating? and
- Does the angular waveform cause problems with the way the device uses power?

At the moment, I don't think there is any way round it but the 'suck-it-and see' approach. Maybe it's an opportunity for someone to produce a useful new website, and perhaps make a little money?

 

[RF Lighting]

Not sure if it's relevant, but my 240V 2D task lamp will not run off my 12DC invertor, yet my 110V one running through a yellow box transformer will

I don't really understand all this stuff BTW

 

[333rocky333]

Not sure if it's relevant, but my 240V 2D task lamp will not run off my 12DC invertor,

mine does, is a switch start one though, even with a 25 foot lead from the van.

 

[RF Lighting]

Ahh. My 240V one is HF. I robbed the bits out of a 2D emergency light so it keeps on running when the power is off.

Not sure if my 110V one is HF or switch start.

 

[ericmark]

Interesting about lamps and 110v transformer. I had wondered if using an isolation transformer may smooth out the wave form.

My son GW7PVD is no longer active on radio so not really a problem for him with RF rubbish. And on RAYNET events I have used my 150W inverter to charge hand held radios while still using them without any problem.

I was just trying to collect as much info as I could before I give him it at Christmas. Once he has it I hope he will tell me how it all works. At least he will not do anything silly.

In caravan I found old fluorescent lamps with supply to heaters were OK but new ones with only one wire to each end of tube were really bad. I expect the inverters are the same with some causing problems and others not?

73 Eric GW7MGW Ex VP8BKM and VR2ZEP

 

[plugwash]

If you are planning to use an inverter a lot I'd seriously consider spending the extra for "pure sinewave" (no inverter will give a completely pure sinewave but good ones should be pretty close). Even if an appliance will work on "modified sinewave" all the harmonics are unlikely to be good for it.