Makita 110v 9 inch grinder

[Hmcivil eng]

I have a 3.5kva generator wich has burnt out 2 new makita grinders .. they are used for cutting 3mm steal box section .. not forced through the metal at all to be fair it hardly scratched the surface. Triped the generator half a dozen times then the grinder got slower slower and nothing just stopped.. if had many 9ich grinders runny off generators in the past ..
Any help would be grateful as I'm told the generator is burning them out

 

[Hmcivil eng]

3.5KVA running 2 9inch grinders.

I doubt the genny is man enough to run this load. Anything else coming off it? 32 amp maximum output (unsure if this is it's continuous rating or not).

Average 9 inch grinder require around 16 amp a little less in reality. So running 2 of them you are really on the limit of the genny. especially with stopping and starting the grinders at the same time.

Why are you using a genny? Location restriction?

Might be better with a fixed transformer.

It's just one 9 inch and it's on the highway so only a genny can be used but should burn the grinder out surely... it was a brand new grinder

 

[Wilko]

Just for balance, I run a 110V Makita 9” grinder off a 3kW transformer. It has worked perfectly for the last few years and cut miles of concrete, or so it feels like now.

 

[Wilko]

It's just one 9 inch and it's on the highway so only a genny can be used but should burn the grinder out surely... it was a brand new grinder

Hi - does it seem the grinder starts normally and runs up to speed? I’m just thinking it might not be at full rpm and can’t cool itself?

 

[Bobster]

It's just one 9 inch and it's on the highway so only a genny can be used but should burn the grinder out surely... it was a brand new grinder

Apologies, I miss read that you were using 2 at once.

1 grinder on a 3.5KVA genny should be no issue.

Have you tested the voltage the generator is outputting?

If it's not quite 110v and more like 90v the current will increase in the grinder an it also will not run up to full speed. Or the other way the voltage is to high and the insulation is becoming damaged in the grinder.

 

[westward10]

Needs taking to a specialist to check it out.

 

[Hmcivil eng]

Apologies, I miss read that you were using 2 at once.

1 grinder on a 3.5KVA genny should be no issue.

Have you tested the voltage the generator is outputting?

If it's not quite 110v and more like 90v the current will increase in the grinder an it also will not run up to full speed. Or the other way the voltage is to high and the insulation is becoming damaged in the grinder.

Its going in to the shop today to be checked but we have 2 other gennys that have been tested in the last 6 mths and one off them gennys did the same thing to a grinder also from screwfix.. I'm just thinking poor quality makita grinder from screwfix

 

[Hmcivil eng]

Hi - does it seem the grinder starts normally and runs up to speed? I’m just thinking it might not be at full rpm and can’t cool itself?

Apears to get up to speed. I thought one off are blokes was putting to much on it and not letting the grinder do all the work .. so when I brought a new one I took it out to site and it lasted 30 mins

 

[davesparks]

It could be a bad batch of makita grinders as they are normally robust.

 

[Megawatt]

Apologies, I miss read that you were using 2 at once.

1 grinder on a 3.5KVA genny should be no issue.

Have you tested the voltage the generator is outputting?

If it's not quite 110v and more like 90v the current will increase in the grinder an it also will not run up to full speed. Or the other way the voltage is to high and the insulation is becoming damaged in the grinder.

QUOTE="Rob, post: 1563222, member: 51701"]
Apologies, I miss read that you were using 2 at once.

1 grinder on a 3.5KVA genny should be no issue.

Have you tested the voltage the generator is outputting?

If it's not quite 110v and more like 90v the current will increase in the grinder an it also will not run up to full speed. Or the other way the voltage is to high and the insulation is becoming damaged in the grinder.
[/QUOTE]
HMCIVAL I'm trying to tell you mitike grinder is a nice grinder and think about it 2 brand new grinders have burnt up and you talking about you are using old generators. It needs earth bonding or the regulator is bad in the generator. Instead of buying grinders and buy a new generator

 

[Lucien Nunes]

This is just a guess but i bet the grounded conductor is not bonded to earth, at 120vac any thing you plug in is probably going to fail.

It has nothing to do with grounding, (bonding means something different in the UK, please don't interchange UK and US terminology!). UK site tools work at 110V in a special configuration used only on building sites. We earth the centre-tap of the generator winding so that both lines are 55V from earth. But we do not use the tap as a neutral, i.e. there are no 55V loads passing current through it. Even if it becomes disconnected it will not affect the voltage at the tool motor, only reduce the level of protection against electric shock to earth. It is not the same as losing a neutral connection on a US 120V service.

Check the voltage at the generator output with and without a tool in operation. If it is very high, then it might be to blame, but to destroy an angle grinder in 30 mins it would have to be so high you would surely realise that something is wrong (or the disc would burst!). I agree some Makita tools are not what they used to be though.

 

[Megawatt]

It has nothing to do with grounding, (bonding means something different in the UK, please don't interchange UK and US terminology!). UK site tools work at 110V in a special configuration used only on building sites. We earth the centre-tap of the generator winding so that both lines are 55V from earth. But we do not use the tap as a neutral, i.e. there are no 55V loads passing current through it. Even if it becomes disconnected it will not affect the voltage at the tool motor, only reduce the level of protection against electric shock to earth. It is not the same as losing a neutral connection on a US 120V service.

Check the voltage at the generator output with and without a tool in operation. If it is very high, then it might be to blame, but to destroy an angle grinder in 30 mins it would have to be so high you would surely realise that something is wrong (or the disc would burst!). I agree some Makita tools are not what they used to be though.

Lucien I was not trying to insult your intelligence and I’m trying to learn the way UK does and in the US if you have a bonding issue the voltage would be reading as high as 180 vac which would easily burn up a drill. Sorry

 

[Lucien Nunes]

Buuuut.... it's a standalone generator. Doesn't matter whether it's in the UK or US. If the generator is producing 110V or 55-0-55 V, the highest voltage the motor can receive is 110V. The only difference the earthing can make in this case is what kind of shock the user does or doesn't receive to earth in the event of insulation failure. The tool motor voltage remains unchanged.

 

[static zap]

.... if you have a bonding issue the voltage would be reading as high as 180 vac

Can see where you are coming from ,was thinking long inductive cable run + some voltage spiking due to a poor connection .. and genny regulator "Biting-Back"
(but has mentioned near genny so dismissed)

 

[Megawatt]

Buuuut.... it's a standalone generator. Doesn't matter whether it's in the UK or US. If the generator is producing 110V or 55-0-55 V, the highest voltage the motor can receive is 110V. The only difference the earthing can make in this case is what kind of shock the user does or doesn't receive to earth in the event of insulation failure. The tool motor voltage remains unchanged.

As long as the voltage stays at 110vac I give up and it just seems strange that 2 brand new drills up

 

[dmxtothemax]

QUOTE - I'm just thinking poor quality makita grinder from screwfix.

Maybe

I'm just thinking poor quality ( imitation ) makita grinder from screwfix