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600w inverter, 500w power tool


Gareth E

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I need to buy an angle grinder for several jobs around the boat. Looking around, the least powerful one I can find, at a reasonable price, is . My inverter is 600w. Will it be safe to use a 500w tool with this? If the inverted were overloaded, higher start up wattage maybe, would something trip out, or could the inverter go up in smoke?

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4 minutes ago, Gareth E said:

I need to buy an angle grinder for several jobs around the boat. Looking around, the least powerful one I can find, at a reasonable price, is . My inverter is 600w. Will it be safe to use a 500w tool with this? If the inverted were overloaded, higher start up wattage maybe, would something trip out, or could the inverter go up in smoke?

 

Read the inverter manual. We can't answer this without knowing which inverter you have!

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Unlikely to go up in smoke. Quite likely to bleep and cut out. A disc cutter is an inductive load so the start up current will be much higher than when it's running. There are a lot of power tools with electronic soft-start now where they appear to hesitate before starting gently. I don't know anything about the technology but I guess these would be more inverter-friendly so might be worth seeking one out. A 600w inverter will normally be around 1200w peak for a very short time. Is the inverter pure sine-wave? Both inductive loads and electronics prefer that.

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I doubt very much that a 600W inverter will power a 500W grinder. Whether or not it would release its magic smoke is unknown. I had a little 200W inverter that I was playing with and someone (not me) plugged in a 1000W load. It never made a sound nor released any smoke but it never worked again. 

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We have an 800 watt modified sine wave inverter, I have an old variable speed 400 watt  Black and Decker drill, and when cutting large holes is quite capable of tripping the inverter. If I take it easy, less force, it works fine. 

So my set up of 2:1 (800 W: 400 W ) just about works, I think you need a bigger inverter, or use a multitool, although my inverter didn't like that, tripped it straight away, so I found some shore power lol.

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5 minutes ago, WotEver said:

I doubt very much that a 600W inverter will power a 500W grinder. Whether or not it would release its magic smoke is unknown. I had a little 200W inverter that I was playing with and someone (not me) plugged in a 1000W load. It never made a sound nor released any smoke but it never worked again. 

We had a small inverter, capable of running a laptop or  my wife's curling tongues in the car, her gas ones were faulty. However, when we tried her other electric ones, it took out the inverter immediately, even though the power was less than 1/4 of the inverter's capability.

The inverter did not recover. I stripped it down, I went straight for the large driver transistors, removed them from the circuit and tested them with the multimeter, and observed that the readings were different for both identical transistors, I took a chance, ordered a pair of transistors, 60p I think... and the inverter repaired and still working, but those curling tongues are banned.

Caution, I am an electronic engineer, so I am aware of the risks, messing with high voltages that are generated by 12 volts can be fatal. There was no guarantee that this repair would work, or continue to work reliably, or that the output voltage of the inverter would be within the manufacturers tolerances.

Richard

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I was going to have a look at mine but the guy who broke it apologised and gave me a 500W sample unit he'd received from China so I didn't bother. 

18 minutes ago, RD1 said:

my wife's curling tongues

It's bad when the wife curls her tongue but when she has more than one...

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There are a lot of fairly cheap but functional pure sine inverters about lately. If you want to work them hard then I suggest you get one rated at twice the power that you intend to continuously draw, they should only be used at full power for a very short time if at all. An angle grinder can be one of the most hard working of any power tool. A bit of polishing or gentle wire brushing is one thing, metal cutting or serious grinding is something else.

..............Dave

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2 hours ago, WotEver said:

I was going to have a look at mine but the guy who broke it apologised and gave me a 500W sample unit he'd received from China so I didn't bother. 

It's bad when the wife curls her tongue but when she has more than one...

Wives can be transferred out of ownership, its often a costly business but overall I think the kind of wife that needs such things as Curling things, hairdryers etc are very expensive to run so cost savings may be had in the long term.

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33 minutes ago, mrsmelly said:

Wives can be transferred out of ownership, its often a costly business but overall I think the kind of wife that needs such things as Curling things, hairdryers etc are very expensive to run so cost savings may be had in the long term.

How many batteries (cheapo's), or gallons of diesel can you get for the cost of a divorce ?

Is it economically viable ?

 

Would you suggest getting a new, more active, model as a replacement ?

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I have a 1kw low frequency inverter/charger it will happily run my wifes 1kw hairdryer without complaining. It will also run the 1200w iron but does complain a bit. A lot of inverters now are high frequency and don't like running full load, easy way to tell is the weight LF inverters have transformers in them so are generally heavier than HF inverters.

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8 hours ago, WotEver said:

I was going to have a look at mine but the guy who broke it apologised and gave me a 500W sample unit he'd received from China so I didn't bother. 

It's bad when the wife curls her tongue but when she has more than one...

is a pair of curling tongues more desirable than a single sharp tongue? 

if so I may go to Boots and trade in the wife.   :rolleyes:

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8 hours ago, Alan de Enfield said:

How many batteries (cheapo's), or gallons of diesel can you get for the cost of a divorce ?

Is it economically viable ?

 

Would you suggest getting a new, more active, model as a replacement ?

The new " more active " model does sound appealing until I realise I would no longer be able to do it justice :(

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Thanks for the replies. It's no an expensive inverter, but I really don't want to blow it up!

The alternative is to use my generator, it's rated at 770w. Would I be right in thinking that if this was overloaded the engine would simply cut out, no harm done?

 

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19 minutes ago, Gareth E said:

Thanks for the replies. It's no an expensive inverter, but I really don't want to blow it up!

The alternative is to use my generator, it's rated at 770w. Would I be right in thinking that if this was overloaded the engine would simply cut out, no harm done?

 

Carefully check any rating claimed for generators.

It is the 'norm' to quote the 'maximum' (short time) power which can be very different to the 'continuous rating' (which is obviously the one you will be 'using')

For example :

My Honda 650 is actually continuously rated at 450w

My Kipor 2000 is actually rated at 1600w.

 

Depending on the generator, overloading it could result in 'just' 'popping' an overload button, or destroying/blowing components. Better to have equipment that is not 'working on the edge', always have a safety margin, particularly for things like angle grinders and drills where you can 'jam' the blade / bit and get a big current draw.

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Measure the DC resistance of the grider across the L and N terminals of the plug (when unplugged, lol :)).

That'll give some idea of the instantaneous startup current of the grinder, using amps = volts/ohms.

After a few milliseconds it'll drop due to the inductance of the motor windings, then drop further as the grinder spins up  - due to 'back emf' from the spinning motor.

With a cheapo non-LF inverter I'd make sure the surge rating exceeds the instantaneous startup current....

Edited by smileypete
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On 25 March 2017 at 15:30, WotEver said:

I think a pair of curling tongues could be quite desirable, yes. I have no use for curling tongs though. 

D@mn auto spelling correct has a lot to answer for lol. 

Actually my wife does have a curly tongue, I wondered what caused that. Thanks for the heads up on that one lol... 

 

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On 27 March 2017 at 13:29, smileypete said:

Measure the DC resistance of the grider across the L and N terminals of the plug (when unplugged, lol :)).

That'll give some idea of the instantaneous startup current of the grinder, using amps = volts/ohms.

After a few milliseconds it'll drop due to the inductance of the motor windings, then drop further as the grinder spins up  - due to 'back emf' from the spinning motor.

With a cheapo non-LF inverter I'd make sure the surge rating exceeds the instantaneous startup current....

Probably not an unreasonable theory test for series wound motors, where there it is a wired field coil in series with a wired armature, with carbon brushes, but would not work for induction motors where it uses a start up capacitor, examples of which can be found on some table mounted bench saws etc. Induction motors usually start off slowly with a big hum at the beginning lol I am not sure what these would do to an inverter though, as it is a very inductive load.

 

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I used a 600W drill on an 800W inverter, starting it by slowly pulling the trigger to build up speed, however one time I forgot and pulled the trigger full on, there was a bit of a pop and all the magic smoke left the inverter...............

On some cheap inverters (the above inverter was cheap) the surge power quoted is only for a few milliseconds and you will often be unable to find any indication in the spec as too how long it can supply a surge -  probably for good reason they don't tell you.

Edited by Chewbacka
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