Invertors & Inductive Loads

[nyx2k]

i have a 240v low pressure air pump i use to blow up the children's large paddling pool. it blows up the dinghy in less than 30 secs. i was hoping to use it in the car but its 195 watts so a lot more when starting and the inverters ive seen say not to be used on inductive loads. what inverter do i buy or do i get a 12v one instead

 

[captainslarty]

There is much crappo talked about inverters Sir.. and you are correct.. the inductive load IS the problem for a quasi sine wave.. If you get a sine wave unit.. it will be fine.. a non sinewave unit will cause overheating of the motor and inverter leading to issues.

 

[nyx2k]

how quickly will the heat build up. could i not use the inverter for a minute or is it definatly a 12v motor i need. i really dont want to spend a lot on a sine wave inverter

 

[William_H]

I wouldn't want to claim to be an expert but as i understand it the concern with inductive loads is more when trying to run an induction motor. As used in washing machine refrigerator aircon, fan or drill press.

Motors that have brushes like electric hand power tools vacuum cleaners kitchen mixers and similar gadgets do not present such a problem.
Brush motors generally run at high speed whereas the induction motors run at 2850 RPM. This is dictated by the frequency of the AC.
(so faster in US on 60 hertz)
My guess is that your air pump has a brush type motor so will run OK on an inverter. Yes the inverter will be loaded on start but should be OK once up to speed. The inverter should be able to cope with an overload by shutting down but monitor its temp anyway. olewill

Brush motors scream at you while induction motor has a lovely gentle hum.

 

[boatmike]

You don't say what size inverter you have, but 195W at 240V is only 1.3 Amps so I am sure it will be OK. The issue with inductive load is really not relevant with a little pump like this. Plug the booger in and if it works OK (which it probably will) you will be fine. I have a 1500W inverter, which is not pure sine wave and I run electric drills, hair drier, vacuum cleaner and yes a dinghy pump from it and it works fine.

 

[nyx2k]

i havnt got an inverter yet but have seen cheap 300watt one for around £25. i'll get one today. thanks all for the help

 

[bedouin]

Where you can have problems with "conventional" motors is if they are rated near or above the capacity of the invertor. In that case if the motor is heavily loaded it will try to draw more current that the invertor cannot supply, making it more likely to "stall" (or whatever the term is for an electric motor).

That should not be a problem in the case of an air pump though.

 

[rogerdog]

Re: Invertors & Inductive Loads

most -even some the cheapest inverters will cope with a transient of double their capacity - so you *should* be ok - but as stated before the real answer is sinewave not barely disguised squarewave (have a look at the output on an oscilloscope and you will see what is meant)

For the short preiod that the pump will run though the overheating etc should be simply academic