Thread: question for a leccie

Not a leccie here, but it sounds like to me that the Safety Switch is getting warm with use and when it gets to a certain temp the current draw from starting the Bandsaw or D/C it keeps tripping it.

even without the machines connected?
Wolffie

Originally Posted by Wolffie

even without the machines connected?
Wolffie

Have known it to happen, if the switch is warm or hot then yes it it can happen with nothing connected because it may be tripping because of the heat and not any actual faults with the machines.

Had another thought, have you ever notice if the lead itself is getting warm or hot? It is a lot of current running through that lead to run the Dusty and Bandsaw. Dusties generally pull a lot of current.

Actually haven't thought about that but, 20 metres is an awfully long cord, right?
Wolffie

You may have to have look and see if you don't have some loose connections causing the heat.

Nar Nothing to do with heat at all

IMO you have a faulty lead.

Safety switches trip(turn off) on earth Leakage.
In layman's terms
The safety switch looks at electricity (Current in this case)going out and compares it to what is coming back.
If there is a big difference the thing switches off.

In your case the electricity is leaking to the earth conductor from the active or neutral conductors (Or both)

In other words the insulation is breaking down

If you know a friendly sparkie he will be able to prove this with with his insulation resistance tester.


Of course If there is no load (Current flowing) the safety switch will not see a problem remember they work on current flow.

It may not happen all the time because of the way the lead is rolled out or the amount of current flowing.

Code:

Safety switches trip(turn off) on earth Leakage.
In layman's terms
The safety switch looks at electricity (Current in this case)going out and
compares it to what is coming back.
If there is a big difference the thing switches off.

Thank you Nev.
That is what I thought too.
I had a suspicion there was a break inside the lead, which would not show all the time but, when we shifted the lead around, say changing from one machine to another, the inside would move, particularly if the breakage is around the plug, or if the fault was in the switch, right?
And that's why the multimeter would not show a fault when sitting on the continuity mark, I am only measuring one wire at a time.
Going out to buy a new lead tomorrow
Wolffie

A safety switch detects the difference or imbalance in current draw between the active and neutral conductors, when the current draw varies by more than a small preset value (about 30Ma I think) the safety switch trips and disconnects the power. If you accidently touch either the active or neutral then an imbalance will occur and trip the rdc saving you from possible electrocution. An imbalance in current draw between the active and neutral wires can exist in a situation where an extension lead is plugged in and left out in the open and damp grass/weeds cause a small current flow from the active or neutral to ground tripping the rcd even though there is no equipment connected to the extension lead. Like nev says its probably your lead and most likely to be at the twin outlet end where possibly sawdust has got into the socket.

It looks like I found the culprit by a process of elimination.
It is the bandsaw.
As soon as I plug it in and without turning the power point on (ie no actual power on the machine) it triggers the safety switch.
Strange though, that cord has never been squashed or anything, could it be the actual magnetic switch on the machine?
Bummer, the machine is only 6 months old and I live in the sticks where it takes weeks just to get a leccie to come and have a look
Wolffie

Sounds like a similar prob that someone else had, it was a build up of sawdust in either the motor or the switch. If you've got a compressor try blowing out the motor and switch with compressed air.

Originally Posted by DJ's Timber

If you've got a compressor try blowing out the motor and switch with compressed air.

We did and it seems to be working now.
What I found when I took the covers off the machine was 2 bung holes from the wheel cavity into the power column and about 15 mm of dust on top of the connections.
Blew all the dust out and plugged up the holes.
Fingers crossed that it will keep on working.
Wolffie

Tried that with mine, and it still isn't working. For me it looks like a trip to the repairer or a new motor off ebay. Actually, may not be a bad time to upgrade the motor power. Not much point having 6 inch high throat when the motor stalls cutting more than about 2" Good luck with yours Wolffie

Peter

After you've experienced problems like these, it's a good idea to perform an insulation resistance test on the motor (& the extension lead while your at it). If foreign matter inside a motor has been causing earth leakage current, it's also likely that some debilitation of the winding insulation may have occurred.

For a single phase motor, no greater than 500v should be used in an insulation resistance test. If the results of the test show less than about 10 Megohms, you may have ensuing problems. If the results are close to 1 Megohm or less, the tested device is dangerous & needs to be repaired or replaced.