Equipment ratings are not always what they seem.

[Mattb4]

I have been using a 900w microwave that was drawing around 1375w when running. This was no problem with my 3kW AIO even when other things were also running. I happened to get a buy on a new 1000w microwave so I put it in the place of the old one yesterday. It is quicker to heat things and runs quieter. However, it does not draw 100w more than the 900w unit, it draws 1650w in comparison to the 1375w for 275w more!

My AIO still powers it by itself without a problem but I will have to watch how things work when other stuff cycles on.

Sometimes you really need to operate equipment before you can know what it does versus what some rating on it would make you think it does.

 

[Zapper77]

I have been using a 900w microwave that was drawing around 1375w when running. This was no problem with my 3kW AIO even when other things were also running. I happened to get a buy on a new 1000w microwave so I put it in the place of the old one yesterday. It is quicker to heat things and runs quieter. However, it does not draw 100w more than the 900w unit, it draws 1650w in comparison to the 1375w for 275w more!

My AIO still powers it by itself without a problem but I will have to watch how things work when other stuff cycles on.

Sometimes you really need to operate equipment before you can know what it does versus what some rating on it would make you think it does.

Time for a inverter microwave

The Best Inverter Microwaves for More Evenly Cooked Meals

Inverter microwaves use consistent power to heat your food, delivering faster cook times and more even results.

www.popularmechanics.com

 

[RCinFLA]

Many appliances get more efficient as their power ratings increase.

Also have to consider the power factor when converting AC to DC within the appliance. You can have high crest factor current spikes at the peaks of sinewave AC input with a simple rectifier-capacitor filter power supply. Smaller btu / cheaper mini-split air conditioners are big offenders for this.

When running from a battery power inverter or generator, power factor of load is an important thing to consider. Inverters, generators, and transformers are rated for VA not watts.

HF inverters are particularly vulnerable to poor power factor loads causing instability in their battery to HV DC converters and voltage spikes due to ringing of their L-C PWM to sinewave AC output filters. They typically don't like PF loads worse than about 0.8. All the complains about flickering lights is likely caused by poor power factor, high current crest factor loads on HF inverters causing AC output voltage regulation instability.

 

[Mattb4]

Many appliances get more efficient as their power ratings increase.

Also have to consider the power factor when converting AC to DC within the appliance. You can have high crest factor current spikes at the peaks of sinewave AC input with a simple rectifier-capacitor filter power supply. Smaller btu / cheaper mini-split air conditioners are big offenders for this.

...

You got me curious. Starting with virtually no load of 4w at a pf of .54 before running microwave on the output of the AIO and then after running I measured 1668w at pf of .92

It would seem the microwave improves the pf over almost no load for the AIO.

 

[LydMekk]

I got a 5 yr old Miele microwave. Bought it new ofc.
When I select 600w heating it draws 1600w (230V).
Not very efficient...doesn't use it much though so it don't matter - only heats some takeaway food sometimes.

 

[hwy17]

Smaller btu / cheaper mini-split air conditioners are big offenders for this.

My mrcool draws an amp in standby, at like power factor .05 or something.

 

[rpdom]

You got me curious. Starting with virtually no load of 4w at a pf of .54 before running microwave on the output of the AIO and then after running I measured 1668w at pf of .92

It would seem the microwave improves the pf over almost no load for the AIO.

The important part of most microwaves is just a honking great transformer that ups the voltage to a couple of kV AC or more to drive the magnetron. That has a PF of close to 1.0.

The controls of the microwave will be running from low voltage DC with a switching PSU. That would have a low PF.

Power levels are usually achieved by switching the microwaves on for some seconds, then off for a while. The inverter won't like that.
I haven't looked at Inverter Microwaves. I'm going to make a guess that they actually control the power to the magnetron somehow instead of just switching on full and off.

 

[robby]

900w microwave is giving you 65% efficiency and the 1000W microwave is 60% efficient.
The levels are probably a bit closer if the new one has extra features consuming power.
Then we have the question of the rated output power accuracy. Depending on what quality and price point the Magnetrons output could be exaggerated.

 

[Mattb4]

900w microwave is giving you 65% efficiency and the 1000W microwave is 60% efficient.
The levels are probably a bit closer if the new one has extra features consuming power.
Then we have the question of the rated output power accury. Depending on what quapity and price point the
Magnetrons output could be exaggerated

I expect based on heating of food that my older 900w rated either was exaggerated or the new 1000w is understated. The wattage difference is also indicative of the quicker food heating.

 

[labeeman]

I have been using a 900w microwave that was drawing around 1375w when running. This was no problem with my 3kW AIO even when other things were also running. I happened to get a buy on a new 1000w microwave so I put it in the place of the old one yesterday. It is quicker to heat things and runs quieter. However, it does not draw 100w more than the 900w unit, it draws 1650w in comparison to the 1375w for 275w more!

My AIO still powers it by itself without a problem but I will have to watch how things work when other stuff cycles on.

Sometimes you really need to operate equipment before you can know what it does versus what some rating on it would make you think it does.

A microwave is rated on the output power of the Magnetrons and ALL rf conversion stuff is at best 60% efficient most times worse.
my older microwave is rated at 1kw it pulls 2kw.