Drill leaks electricity to case

[Ignoramus15109]

OK, I will keep you in mind. I am cleaning it right now. Lots of carbon dust flew out after I blasted it with compressed air.

i

[Pete Keillor]

Harold, I had one like that last year, only it was the power wiring to a 460 V. 15 Hp. motor crushed in the motor junction box cover. Luckily, the AB Powerflex 700 VFD was smart enough to instantly trip, so no light show. This was on a new installation.

Pete Keillor

[Joseph Gwinn]

Sounds right to me. Which leads me to a question:

Is the power cord two-wire, or three-wire? If three wire, there is little danger of shock, as the ground wire will short the leakage path.

If it's two-wire, I would also rewire the drill, changing to a three-wire cord would also change the cord to be three-wire, thus grounding the case. Because carbon dust will re-accumulate.

Joe Gwinn

[Ignoramus22178]

It was the case. You two are right. After I blew away the dust with my compressor, the drill stopped tripping GFCI. See my separate post FIXED -- THANKS -- drill leaks electricity to case.

It is three wire, but I forgot to check whether there is conductivity between the case and the ground prong. (I hope so, but I want to make sure of that). I will try to do so tonight. I know that the ground wire from the power lead is securely attached to the case, though, so the check will be more of the CYA variety.

I agree 100%. Most likely it is properly grounded, but I will check with an ohmmeter to make sure.

i

[Lloyd E. Sponenburgh]

It couldn't trip a GFCI unless a ground path is available. Assuming YOU weren't the ground path , then it would have to have been a 3-wire cord, or the GFCI would never have tripped.

LLoyd

[Ignoramus22178]

Good point... Still, I feel like I need to cover my ass and double check this, but yes, it is most likely properly grounded. As a drill with metal case, it should be grounded.

i

[Bruce L. Bergman]

You are wrong, transformer breath! ;-P (PPppbltltlt!!)

The GFCI is comparing the exact amount of power going out on the hot wire and coming back on the white wire, Period. They have two opposing windings on the same current transformer core, and under normal operation the currents 'out' and 'in' cancel themselves out to a sum zero. GFCI's can work on a poorly grounded system on an older house, though it's not the preferred connection.

Let the power leave on the hot wire and NOT come back on the neutral, there is current sensed in the transformer. And if it's over

3ma for a Class A device the electronics trips the protection.

The leaked current does not need to come back on the ground connected to that GFCI. It can ground out to any handy ground source

- a copper water pipe, or a steel stud or structural member tied to ground in the building, or a grounded natural gas line...

-->--

[Joseph Gwinn]

True.

The return current has to pass through that one white wire (ground) that was associated with the black wire (hot) that shared the GFCI in question. If some current on the black wire bypasses that GFCI by using some other path to the ground in the panel than the associated white wire, pop goes the GFCI.

So, leakage from drill case, through Igor, and to ground via the waterpipes et al, sets up a race condition: Which will pop first, Igor or the GFCI?

This is the reason to have a well-grounded case. The real danger is more often that a 110-volt shock will cause a fall or other accident than direct electrocution.

Joe Gwinn

PS: To take an extreme example, if one puts a resistor from the black on one circuit to the white of another, both GFCI breakers will pop. At least in theory, but I recall that many GFCIs are designed to ignore added current on the white, only reacting when there is more current leaving on the black than is returning via the associated white.

For the electronically-obsessed, this is achieved by means of a synchronous detector rectifying the amplified unbalance signal from the current transformer, the detector feeding a low-pass filter and a threshold detector. The sign of the detector output varies with the direction of the unbalance of leaving and returning currents.

If I recall, ten milliamps will do it, so a 110/0.010= 11,000 ohm resistor capable of at least 110^2/110= 1.1 watts will do, so a 10K

2-watt resistor will do nicely for an experiment.

[Lloyd E. Sponenburgh]

And, as Dexter would say, "You are STOOOPID!".

Some imbalance must occur between hot and neutral to kick any GFCI... you even stated that. Ok... now read my post again. IF there's no _other_ ground path (like the user, or the drill sitting on a grounded conductive surface) through which part of the current might leak, AND the GFCI is still tripping, then there MUST - HAS TO BE - a ground path somewhere in the cord/wiring.

It's simple to understand that current flowing on the hot - which doesn't have _any_ other path to follow except the neutral - must be matched by current on the neutral. Balanced currents, no trippy the giffy. Short user to case to ground, and THEN you have the very situation a GFCI was designed to protect against.

LLoyd

[Ignoramus12893]

Not exactly true. The white wire is called Neutral (not ground). It is a current carrying conductor. There is also a green wire, called ground, that is not supposed to normally carry current. If some current leaks and flows through that non current carrying conductor, or through me, it is called a "ground fault".

I agree with that completely, the dangers from being hit by 110v go way beyond mere electrocution.

i

[Bruce L. Bergman]

Let's Find Out! I have this deliberately shorted drill, and it's in front of a grounded platform with an inch of standing water.

Here, let's hand it to my assistant Timmy and have him drill a hole

- Oh, and Timmy you need to take off your shoes and socks for this experiment, wouldn't want your shoes getting wet, now would we?...

--

[clare at snyder.on.ca]

Doesn't even have to be directly grounded, Bruce. A capacitive ground will do it too. In otherwords - leakage to a non-grounded item/person.

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