Power draw and inverters

[pessimist]

These may seem stupid questions but I can't find answers anywhere.
I am aware that some appliances draw much more than their stated power on start up, but is there any way of finding how much. As an example I have a 1600w inverter - could I run a 1kw air fryer or a 600w microwave?
If I manage to run these appliances is there any way of finding out what their actual power draw would be. If I use a toaster or a kettle I expect them to draw their rated power for as long as they are switched on. I would assume that a microwave or air fryer's power demand would be intermittent, but is there any way of estimating what they might actually use?
Thanks

 

[rogerthebodger]

First always look at the input power requirements this can be alot less than the output power.

Microwaves are a clastic example.

Any normal heating appliance are usually resistive so the input power is normally the same as the output power.

The difficulty comes with inductive equipment like electric motors which could have a high start current/power

There are ways so lowering the start current of motors and there are ways of installing a soft start device or a variable speed device by using a variable frequency inverter

Check if your inverter has an overload shut down if so if you pull too much current it will shut down the you know

Also some inverters have aan continuous rating and /or an intermediate rating

 

[ctva]

You could use a clamp meter to check the startup current (I think as it is not something I have ever done) or the user manual of the appliance should give the currents at startup and normal load.

 

[Alan S]

First always look at the input power requirements this can be alot less than the output power.

Microwaves are a clastic example.

Are you sure about that?

 

[PaulRainbow]

These may seem stupid questions but I can't find answers anywhere.
I am aware that some appliances draw much more than their stated power on start up, but is there any way of finding how much. As an example I have a 1600w inverter - could I run a 1kw air fryer or a 600w microwave?
If I manage to run these appliances is there any way of finding out what their actual power draw would be. If I use a toaster or a kettle I expect them to draw their rated power for as long as they are switched on. I would assume that a microwave or air fryer's power demand would be intermittent, but is there any way of estimating what they might actually use?
Thanks

Ball park figures:

A 1600W inverter (assuming it really can deliver 1600W continuous) will power appliances up to 1.6Kw at 240v. That also assumes no big startup currents, like some electric motors will have, unless the inverter has a peak power rating that can cope with the current inrush.

A 1kw 240v appliance will typically draw around 100a from a 12V battery setup.

 

[rogerthebodger]

Are you sure about that?

Yes you are correct brain fade

Imput power will be more than the output power microwav at home is 1500w input 1000w max output

 

[superheat6k]

Also be aware that many inverters are modified square wave output and some electronic devices, such as Magnetron's the device that makes a microwave work, do not get along with square waves. The rating of interest for any Inverter is the Continuous rating, rather than the Peak rating used to sell the thing. Also be aware a fully charged battery at say 13.5vdc may easily drop off to below 12v when 100a (as PR mentions) is being drawn, so if the terminal voltage drops off too much then the performance of the Inverter will follow.

So couple this input power capability into the microwave say 1000w or higher for 600w output you can see it is easy to look at the most optimistic ends of both devices rating values. 1600 out of one (Inverter) meets 600 out of the other (Microwave), when in reality the 1600w becomes 1000w (or less) and the 600 becomes 1000w (or more).

The issue that will be met is obvious, especially as the 12v source is still likely driving the rest of the 12v domestic load.

 

[Kelpie]

Air fryer does what it says on the tin, as do other devices using primarily resistive heating elements.
Our air fryer happily runs off our inverter, it's been a great addition to the boat.
Things like fridges and freezers can have big startup currents, I've heard figures like 4-5x the continuous rating. Fortunately they only tend to run at 100-200w so even with the startup surge they'll be within the rating of a medium or large inverter- and generally they're 12v anyway.

 

[William_H]

Both Air frier and microwave cooker should draw a similar current on start up to run. Yes they have induction type fan motors but these are quite small compared to heating load. As said microwave cookers won't like anything but pure sine wave supply. ol'will

 

[oldmanofthehills]

These may seem stupid questions but I can't find answers anywhere.
I am aware that some appliances draw much more than their stated power on start up, but is there any way of finding how much. As an example I have a 1600w inverter - could I run a 1kw air fryer or a 600w microwave?
If I manage to run these appliances is there any way of finding out what their actual power draw would be. If I use a toaster or a kettle I expect them to draw their rated power for as long as they are switched on. I would assume that a microwave or air fryer's power demand would be intermittent, but is there any way of estimating what they might actually use?
Thanks

It does mean much in terms of overall load but start up can affect supply chain

We had a big shock when we started using computerised signalling equipment on uk rail and found it affected by spikes. It turned out our 5A 110v point machines drew maybe 10000amp momentarily at start up - off the scale of our recording equipment.

Usual anti interference measures adopted but it seemed to defy physics on 20A supply

 

[pessimist]

Thanks everyone. A secondary if I may. Anybody have any idea of the power usage of , say, A 500w microwave over a a half hour period. I'm assuming that it will not draw full power over the whole period. Same question for air fryer.

 

[oldmanofthehills]

Thanks everyone. A secondary if I may. Anybody have any idea of the power usage of , say, A 500w microwave over a a half hour period. I'm assuming that it will not draw full power over the whole period. Same question for air fryer.

I think you will find a 500 micro draws 2A all the time. It has no thermostat or sensing unlike conventional open which reduces power when temperature reached. One of reasons why ovens just as economical for big loads

 

[geem]

You need to know more about your inverter. Is it 1600w continuous? Does it have a peak rating? I am guessing it is a nigh frequency inverter not low frequency. For large motor loads, you need a low frequency inverter these will handle the inrush current of a motor far better. A high frequency inverter will run large motor loads for a while before it goes pop.
For resistive loads you will be fine with a high frequency inverter as long as the load is within the continuous rating of the inverter

 

[Daverw]

We found that our flat bed microwave draws less input power that the same 750w one with turntable, apparently down to the way it sends the beams

 

[Kelpie]

Thanks everyone. A secondary if I may. Anybody have any idea of the power usage of , say, A 500w microwave over a a half hour period. I'm assuming that it will not draw full power over the whole period. Same question for air fryer.

We don't have a microwave so can't comment there.
The air fryer draws 110A pretty much continuously, until after several minutes it has warmed up and then seems to go down a gear, cycling between almost nothing and about 60A. From memory it needs to running at least ten minutes before it starts to cycle. It might be that it only cycles as it approaches the end of time period that you set at the start.
Did I mention that we love it? Proper chips, no more soggy gas cooker abominations.

 

[pessimist]

The inverter is a Sterling 1600 pure sine wave. Claims 1600w continuous and 2000w peak. Sounds as though I should be able to run an air fryer or microwave. Useful to know that the air fryer does cycle.

 

[Kelpie]

As another data point, our induction hob (Vango Sizzle) steps up and down in power depending on what you set it at, so 66A per ring on full, 44A at lower power, etc. And once hot it will also cycle a little.

 

[Rappey]

My 750w microwave (with turntable) shows it uses 1500w according to the smart meter.

 

[Trident]

My guess is the Sterling will only run 1600w continuously for about 10 minutes and then get too hot. Most air fryers are 1460 w or bigger so really too big for what you have. My 800w microwave draws around 100A at 13.5v continuously in use so clearly input power is much higher than the rated power.

Bear in mind with all this you will need to check the fusing and wires from battery to inverter as most I have seen are woefully undersized for continuous high load like cooking. Really good clean connections too. I live full time on an all electric galley boat so use induction hobs, air fryers , microwaves etc every day. I have a 3kw inverter with 120mm cable to it, 300a fuses in a 500a rated holder, a 650a cut off switch and I upgraded all the AC wires out to 32A rating rather than the normal 16A stuff. It all works great but these are all big loads so don't skimp on the safety side and check on wire temperatures and so on as you first use it

 

[Kelpie]

My guess is the Sterling will only run 1600w continuously for about 10 minutes and then get too hot. Most air fryers are 1460 w or bigger so really too big for what you have. My 800w microwave draws around 100A at 13.5v continuously in use so clearly input power is much higher than the rated power.

Bear in mind with all this you will need to check the fusing and wires from battery to inverter as most I have seen are woefully undersized for continuous high load like cooking. Really good clean connections too. I live full time on an all electric galley boat so use induction hobs, air fryers , microwaves etc every day. I have a 3kw inverter with 120mm cable to it, 300a fuses in a 500a rated holder, a 650a cut off switch and I upgraded all the AC wires out to 32A rating rather than the normal 16A stuff. It all works great but these are all big loads so don't skimp on the safety side and check on wire temperatures and so on as you first use it

That's pretty impressive.
I've only got 70mm² although I never draw more than 200A.