Sorry no, nothing to do with girls getting high ;)
Got a 3kva generator and am trying to run a 1500w table saw from it.
Genny trips out on pressing start on the saw. Saw works fine when plugged in to house. Genny been fine with everything else plugged it to it.
What (if anything) can I put in line to stop the trip on start up as I figure it's just that initial surge.
TIA.
Induction motor? Start load 6 x running load IIUC?
Happens a lot with pressure washers.
You could just remove the trip switch.... or preferably fit a less fussy one.
Very few females called Genny these days. My Mum was one, though! .-)
It is, and there is not much you can do except maybe have a resistor in series - a high wattage bulb - and a switch to short it out once the motor is up to speed.
Another option is the old aircraft trick of a rotary converter where the inertia of it keeps the voltage up past the surge. But that itself needs to start up as well..
can be a lot more than that.
I suppose you could try a 1kW fire element in series; switch it out once the saw was turning. Or get someone else to. Don't want you losing an arm.
Bill
I had a similar issue with a chop saw - it was the mains mcb that tripped in this case.. Sort of solved by running the saw from a longish (and cheap!) extension cable reel - seemed to have just enough resistance to give the mcb time to not drop out. Saw didn't seem to suffer once it was up to speed.
Adrian
Is it an induction motor saw?
They can take anything from 5 to 9 times the normal full load current on starting, coupled with the likelihood of it being a non unity power factor. Hence that 1500W might be at 0.65 PF or similar,
Might be interesting to see if the motor starts on its own from the genny (i.e. assuming its belt drive, then without the belt one). If it does then some form of belt tensioner that would allow the motor to be unloaded at startup and then the blade drive engaged.
But normally that just switches which socket is live the blue 240 one or the yellow 110v...
: > :> Got a 3kva generator and am trying to run a 1500w table saw : > from : > :> it. : > :>
: > :> Genny trips out on pressing start on the saw. Saw works fine : > when : > :> plugged in to house. Genny been fine with everything else : > plugged : > :> it to it. : > : : > : Is it an induction motor saw? : > : : > : They can take anything from 5 to 9 times the normal full load : > current on : > : starting, coupled with the likelihood of it being a non unity : > power : > : factor. Hence that 1500W might be at 0.65 PF or similar, : > : : > :> What (if anything) can I put in line to stop the trip on : > start up : > :> as I figure it's just that initial surge. : > : : > : Might be interesting to see if the motor starts on its own from : > the : > : genny (i.e. assuming its belt drive, then without the belt : > one). If it : > : does then some form of belt tensioner that would allow the : > motor to be : > : unloaded at startup and then the blade drive engaged. : >
: > No belt drive unfortunately :( : : How loud is the motor when running - quite and smooth like a bit of : machine shop equipment, or screams at you like most hand held power tools?
Hmm, I'd say she's a bit of a screamer, the saw is quite noisy too ;)
: Failing that, what make/model of saw?
Nowt special, a NuTool HS1500. Having said that, it does a good job, just not when attached to the genny.
Blade just bolts straight on to the motor. Was the same on a Performance Pro table saw I had.
: Just trying to work out what sort of motor it actually is... If it *is* : an induction motor, then it would be unusual to have a direct drive. If : its a universal motor then the problem is simpler to solve since the : inrush is less anyway, and a bit of extra resistance in the supply will : often solve the problem. : : For example, trying the long extension lead trick mentioned elsewhere : might work. Also with a universal motor, you may find an off the shelf : power tool speed controller can be used to start it on slow and then : ramp it up. Or, you could make a step start box (basically a couple of : relays, a high power resistance of some sort (a traditional light bulb : (or a few in parallel) may pass enough current to get it spinning with : no load), and a second relay that closes after a short time delay to : short out the extra resistor and apply full power to the tool)
Just tried a 10m extension, didn't seem to make any difference :(
... making it easy to implement
NT
Right ok, forget all the induction motor stuff, this is a universal motor jobbie.
Yup, I have something similar on the shelf (does not get much use since I get a unisaw, but kept since it is transportable)
And yup, its loud!
Worth a try, but probably not enough resistance for this application. I would expect the universal motor probably pulls two to three times full current at startup (they usually start with a "bang" as they delivery maximum torque from stalled, and least torque when running (the opposite of what you want in a saw really, but that is another matter!))
If you add more permanent resistance inline with it then you will probably reduce the performance. I would be inclined to try a quick lashup with a batten holder and a 100W light bulb inline with its supply
- see if firstly that will get it spinning at a decent speed with no load, then secondly if the genny will hack it. If it does you can make something more "elegant" to allow a two stage start.
Are you suggesting a blue/yellow Y cord? I'd look very closely at the wiring between the alternator, switch and sockets. One assumes that the 110/240 adjustment is done by series (240) and parallel (110) connection of two windings from the alternator.
: > Just tried a 10m extension, didn't seem to make any difference :( : : Worth a try, but probably not enough resistance for this application. I : would expect the universal motor probably pulls two to three times full : current at startup (they usually start with a "bang" as they delivery : maximum torque from stalled, and least torque when running (the opposite : of what you want in a saw really, but that is another matter!)) : : If you add more permanent resistance inline with it then you will : probably reduce the performance. I would be inclined to try a quick : lashup with a batten holder and a 100W light bulb inline with its supply : - see if firstly that will get it spinning at a decent speed with no : load, then secondly if the genny will hack it. If it does you can make : something more "elegant" to allow a two stage start.
Short on time for the rest of this week but will give it a go as soon as possible and get back to you.
Thanks for the help so far.
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