Re: ELCB Issues

Thanks for this.

I guess the thing that bothers me is that once the machine is up and
running, like this morning for example, everything works normally and
the trip stays in. So it seems that in normal circumstances there is
no imbalance between live and neutral, it seems to be something that
happens just when the charge pump relay powers up the inverter and
the stepper power supply, hence my suggestion of some kind of
transient.

Once powered up the Inverter (spindle) can be switched on and off
with no ill effects, the steppers similarly work without problems.

Ian

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mark Vaughan" <mark@...>
wrote:

>
> Hi Lester and Ian
>
> As Lester say the cause is an Earth fault, but it is easy to get

some

> confusion here, so first you must consider how the ELCB works.
>
> It does not detect current in the Earth wire, it looks at the live

and

> neutral, the current travelling in each should be the same, if some

is

> leaking to earth then live and neutral will be imbalanced and the

trip will

> go.
>
> So you have to be looking for something, insulation failing

probably between

> Live and Earth, or perhaps a short occurring between Neutral and

Earth.

>
> Like Lester I have found loads of problems with USA kit, and lots

of stuff

> that would never come near their UL safety specs.
>
>
>
> Things to look for.
>
> Failed Suppression capacitors on motors filters and the like. These

will

> often be wired in a Y with a cap between the phases, and one from

each phase

> to earth, a failure here and the ELCB will go. In the UK we use

special

> capacitors that fail short circuit, or open circuit, but others

seem to just

> use a hi voltage cap.
>
>
>
> Insulation in the motor, hopefully it will be a chaffed wire, or

spur on the

> terminals.
>
>
>
> VFD's will dump enormous energy on power up, all you can do for

these is put

> a separate supply in for the machine with an ELCB rated to allow a

higher

> earth current.
>
> Some motors while they have good insulation have enough capacitance

between

> the windings and earth to trip an ELCB, again a high rated ELCB is

required.

>
>
>
> If you use a high rated ELCB (really lower rated in terms of

safety), only

> use it as a supply for the machine, and only do this if you are

sure there

> is no fault and have tested the insulation resistance with a proper
> insulation tester, 600V test should be OK though I normally check

at 1KV and

> higher. Remember this supply is no longer as safe, whilst you

wouldn't want

> to do it, you can stick your finger in the mains on most ELCB house

supplies

> ans it will trip before anything nasty happens, you just get a

joult. On my

> mill for the VFD I had to up the trip current to 750mA, this

provides very

> little protection, fingers in there and it will kill, so every

thing is

> double insulated just in case, about the only protection it gives

is to shut

> the supply off if the wires catch on fire.
>
> There are also certain legal issues if you change the ELCB supply

now in the

> UK under Part P of building regs. Many people ignore this, but you

should be

> aware and if in any doubt at all, safety is the issue, the law I

feel is

> second to that, and if you have any doubts seek professional help.
>
>
>
>
>
> Dr. Mark Vaughan Ph'D. B.Eng. M0VAU
>
> Managing Director
>
> Vaughan Industries Ltd, reg in UK no 2561068
>
> Water Care Technology Ltd, reg in UK no 4129351
>
> Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
> Phone/Fax 44 1872 561288
>
> _____
>
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Lester Caine
> Sent: 18 March 2007 08:34
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] ELCB Issues
>
>
>
> xj5373 wrote:
> > Hi,
> > I have stripped out the old control system from a Denford

Easimill and

> > replaced with Mach3 via a Bob Campbell break out board. It works
> > beautifully but from the start I had a problem with the machine
> > dropping out the ELCB on the mains supply. The machine is plugged

into

> > a ring main which is fed via an earth leakage circuit breaker

from our

> > consumer unit (I should say that I am in the UK). I found that if

I

> > Estopped Mach3, this drops a relay connected to the change pump

which

> > takes the power off the stepper power supply. Giving it a minute

or two

> > allowed me to isolate the machine from the mains without the ELCB
> > dropping.....more often than not. Isolating immedaitely after

Estop

> > seemed more likely to drop the ELCB. I have opeated this way

since last

> > summer but just now I can't reset without losing the ELCB. I have

the

> > machine powered up but in Estop mode, pressing reset powers the

relay

> > via the charge pump output of the break out board which switches

240V

> > onto the stepper power supply and the inverter which is

controling

> > spindle speed.
> > I know what the ELCB does but what is it that is tripping it? Any

help

> > or hints greatly appreciated.
>
> The only thing that will trip the ELCB is an earth fault. So there

must be

> something giving feedback into the protective earth. The first

thing I would

>
> be looking at is what is connected to that earth. I don't like the

mains

> arrangements on any of the American boards I've seen and none of

them pass

> the
> European creepage and clearance rules. Which need to be need to be

a good 2

> times that needed for 110V ;) So I tend to stick to external mains
> components
> such as solid state relays and just run DC from the boards. Then

you can

> ensure clean live and neutral connections.
>
> --
> Lester Caine - G8HFL
> -----------------------------
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