Power inverters?

oldtrack123 · Guru

Power inverters?

D and D · Guru

native pepper wrote:
An RCD is a residual current devise, in other words it disconnects when there is an unbalanced current in the system, or an energy leak. In plain English, they stop you from being electrocuted.

It is wrong to assume that an RCD operating as designed will prevent all electrocutions - it won't. It will only work if there is a short circuit to earth that it can detect. If the fault doesn't result in the current flowing to earth (as described in some of the more knowledgeable comments above) then the RCD won't function and won't prevent an electrocution. I have investigated too many electric shocks (fortunately none to serious) were the injured person has believed they could take risks because there was an RCD in the circuit and they were therefore protected from electric shock.

Dave

oldtrack123 · Guru

HI Dave
Or to put it another way
A RCD will only protect you from SHOCKs to "EARTH" , when /if you contact the 240v active line & "earth"
Providd the SYSTEM IS WIRED CORRECTLY
"
But "Earth "does not ALWAYS mean terra firma [mother earth]
It can be anything that is ELECTRICALLY" EARTHED"

There is NOTHING that can protect one from shock IF one contacts both 'LINES" of a 240V system

PeterQ

brian · Guru

I am amazed at how many people ask a question, fail to read the answers provided and then ask the question again and again. The explanation of what an EN connection is has been given numerous times in this thread, what more can be said to put it more clearly?

dorian · Guru

I have attempted to summarise the information in this thread using diagrams. Any corrections will be gratefully received.

Circuit (1) shows a correctly wired installation with an Earth-Neutral junction at the inverter and an RCD located immediately downstream. There is no fault condition.

Circuit (2) shows a fault condition in which a leakage current of IL is flowing to earth and returning to the inverter via the EN strap. There is a corresponding current imbalance in the RCD. If IL exceeds 30mA, then the RCD trips.

Circuit (3) is identical to circuit (1), but without the EN strap. This means that the inverter is isolated from earth.

Circuits (4), (5), and (6) show fault conditions, none of which cause a current imbalance in the RCD. Therefore the RCD will never trip.

Circuit (4) shows a single faulty appliance. Since there is no circuit for any leakage current, this fault condition is not harmful.

Circuit (5) shows two faulty appliances, each with a leakage path to earth. A person could be harmed if they were to come between earth and either of the two leakage paths.

Circuit (6) shows two faulty appliances, with neither having a leakage path to earth. In order for a person to be harmed, they would need to come into contact with both leakage paths simultaneously.

RCD     = Residual Current Device aka safety switch / Earth Leakage Circuit Breaker (ELCB)
A1, A2  = Active 1 and Active 2 inverter/generator outputs
line    = supply side of RCD
load    = appliance side of RCD
I       = load/line current
IL      = leakage current
EN      = Earth-Neutral junction


                 _____________   A1 load
 A1 line o-------|           |-------o------+
                 |   I --->  |              |
                 |           |             |-|
                 |    RCD    |             | | Appliances                        (1)
                 |           |             |-|
                 |   <--- I  |              |
 A2 line o---+---|___________|-------o------+
             |                   A2 load
 EN junction |
            _|_
             =
           Earth



                 _____________   A1 load           IL --->
 A1 line o-------|           |-------o------+-----------------+
                 |   I --->  |              |                 |
                 |           |             |-|                |
                 |    RCD    |             | | Appliances     |
                 |           |             |-|                |
                 | <- I - IL |              |               Leakage             (2)
 A2 line o---+---|___________|-------o------+               Current
             |                   A2 load                      |
 EN junction |                                                |
             +------------------------------------------------+
            _|_                <--- IL                       _|_
             =                                                =
           Earth                                            Earth



                 _____________   A1 load
 A1 line o-------|           |-------o------+
                 |   I --->  |              |
                 |           |             |-|
                 |    RCD    |             | | Appliances                        (3)
                 |           |             |-|
                 |   <--- I  |              |
 A2 line o-------|___________|-------o------+
                                 A2 load
              



                 _____________   A1 load           IL = 0
 A1 line o-------|           |-------o------+-----------------+
                 |   I --->  |              |                 |
                 |           |             |-|                |
                 |    RCD    |             | | Appliance      |
                 |           |             |-|                |
                 |   <--- I  |              |               Leakage
 A2 line o-------|___________|-------o------+               Resistance           (4)
                                 A2 load                      |
                                                              |
                                                              |
                                                             _|_
                                                              =
                                                            Earth



                                                    IL --->
                                            |--------------------------+
                 _____________   A1 load    |                          |
 A1 line o-------|           |-------o------+----+                     |
                 |   I --->  |            X |    |                     |
                 |           |             |-|  |-|                    |
                 |    RCD    |             | |  | |     Appliances     |
                 |           |             |-|  |-|                    |
                 |   <--- I  |              |    |                   Leakage
 A2 line o-------|___________|-------o------+----+  Y               Resistance   (5)
                                 A2 load         |                     |
                                              Leakage                  |
                                             Resistance                |
                                                 |                     |
                                                 |       <--- IL       |
                                                 +---------------------+
                                                _|_                   _|_
                                                 =                     =
                                               Earth                 Earth



                                                    IL --->
                                            |--------------------------+
                 _____________   A1 load    |                          |
 A1 line o-------|           |-------o------+----+                     |
                 |   I --->  |            X |    |                     |
                 |           |             |-|  |-|                    |
                 |    RCD    |             | |  | |     Appliances     |
                 |           |             |-|  |-|                    |
                 |   <--- I  |              |    |                   Leakage
 A2 line o-------|___________|-------o------+----+  Y               Resistance   (6)
                                 A2 load         |                     |
                                              Leakage                  |
                                             Resistance                |
                                                 |                     |
                                                 |       <--- IL       |
                                                 |                     |
                                                 +---- human body -----+

-- Edited by dorian on Saturday 4th of January 2014 01:48:30 AM

brian · Guru

One point that I would make there Dorian is that whilst your post is a good re-iteration of previously supplied information,:- In diagram 5, depending on the value of the leakage resistances, the upstream overload devices (either integral to the inverter or if the RCD is an RCBO), may well automatically disconnect the supply before anything can be touched.

oldbobsbus · Guru

brian wrote:
I am amazed at how many people ask a question, fail to read the answers provided and then ask the question again and again. The explanation of what an EN connection is has been given numerous times in this thread, what more can be said to put it more clearly?

That may well be true Brian,

You know I respect your opinion and your extensive knowledge of electrics..

BUT

Wouldn't a simple answer like:-

EN = Earth Neutral connection is when one of the active wires is connected to earth to create an Earth Neutral link.

Instead of going into a 500 word essay on electrics and hidden in there is the answer....

Simple question simple answer...

brian · Guru

oldbobsbus wrote:
brian wrote:
I am amazed at how many people ask a question, fail to read the answers provided and then ask the question again and again. The explanation of what an EN connection is has been given numerous times in this thread, what more can be said to put it more clearly?
That may well be true Brian,
You know I respect your opinion and your extensive knowledge of electrics..
BUT
Wouldn't a simple answer like:-
EN = Earth Neutral connection is when one of the active wires is connected to earth to create an Earth Neutral link.
Instead of going into a 500 word essay on electrics and hidden in there is the answer....
Simple question simple answer...

I could have done that Bob, but I doubt that answer would have assisted people in knowing why it is done, and for my part, I am never satisfied with just being told it is so without knowing why it is so.

I consider that an understanding of the reasons behind a particular action being taken may well prevent someone doing something silly or dangerous simply because of a lack of such understanding, and this is one particularly unforgiving area where cognizance is essential..

How many times on this and other fora have you seen folks giving utterly incorrect advice on a subject? They don't normally do it out of malice, but from a general lack of understanding of the subject in question. This doesn't just occur in electrical threads but covers just about the entire gamut of subject matter.

It is often just not possible to explain some things in pure lay-speak, and if my answers further serve to confuse the reader, then it is likely a good idea that they leave it alone.

KFT · Guru

brian wrote:
oldbobsbus wrote:
brian wrote:
I am amazed at how many people ask a question, fail to read the answers provided and then ask the question again and again. The explanation of what an EN connection is has been given numerous times in this thread, what more can be said to put it more clearly?
That may well be true Brian,
You know I respect your opinion and your extensive knowledge of electrics..
BUT
Wouldn't a simple answer like:-
EN = Earth Neutral connection is when one of the active wires is connected to earth to create an Earth Neutral link.
Instead of going into a 500 word essay on electrics and hidden in there is the answer....
Simple question simple answer...
I could have done that Bob, but I doubt that answer would have assisted people in knowing why it is done, and for my part, I am never satisfied with just being told it is so without knowing why it is so.
I consider that an understanding of the reasons behind a particular action being taken may well prevent someone doing something silly or dangerous simply because of a lack of such understanding, and this is one particularly unforgiving area where cognizance is essential..
How many times on this and other fora have you seen folks giving utterly incorrect advice on a subject? They don't normally do it out of malice, but from a general lack of understanding of the subject in question. This doesn't just occur in electrical threads but covers just about the entire gamut of subject matter.
It is often just not possible to explain some things in pure lay-speak, and if my answers further serve to confuse the reader, then it is likely a good idea that they leave it alone.

I'll second that and add-If you do not understand it then you most likely should not fiddle with it. Ask someone who is qualified to fiddle with it.

frank

oldtrack123 · Guru

KFT wrote:
Ill second that and add-If you do not understand it then you most likely should not fiddle with it. Ask someone who is qualified to fiddle with it.
frank

HI Frank

Add MY vote TOO

Ontos45 · Guru

I sometimes wonder how we are all still alive! People have been using 240VAC power in vans long before the powers that be decreed RCD's compulsory and how many of us just earthed the generator, connected it up to van and away we went. Not saying that the advances aren't beneficial but it seems a bit over-board sometimes, not only in this field but others too. Just a thought.

KFT · Guru

Hi peter and sue

unfortunately some of us aren't alive anymore because we did things "that way" back then.

These compulsory things have only been made that way to keep more of us alive.

you see not everyone reads the instructions or understands them let alone follow them. experience has proven that some of the things we used to do are downright dangerous under certain circumstances.

what you said is quite true "I sometimes wonder how we are all still alive!" I think is only through good luck in lots of cases.

frank

brian · Guru

Ontos45 wrote:
I sometimes wonder how we are all still alive! People have been using 240VAC power in vans long before the powers that be decreed RCD's compulsory and how many of us just earthed the generator, connected it up to van and away we went. Not saying that the advances aren't beneficial but it seems a bit over-board sometimes, not only in this field but others too. Just a thought.

You are absolutely correct.

Many of us also drove cars before seat belts became the norm, and survived.

Do you still do that?

Many of us smoked before the risks became well publicised, do you still do that?

Are the compulsory wearing of seat belts and other personal health concerns that have been recognised and safeguards implemented also overboard?

All of us are quite at liberty to ignore the safety warnings at our own risk.

At the very least, do it with full recognition of the possible dangers into which you may place yourself and others, and be willing and able to face the consequences of such action, which may just possibly be the loss of your life, or worse still, that of a loved one.

Many very smart people with many years of experience and access to all of the data relating to electrical accidents have pooled their knowledge to produce safety equipment and rules to limit the dangers involved with using electricity.

Why ignore that?

Make a mistake with your plumbing and you might get wet, make a mistake with electricity and you might get dead.

dorian · Guru

What would happen to you if you were subjected to a sustained shock where the current was above the "let go threshold" but below the RCD's trip point?

KFT · Guru

Dorian, one of the major benefits of a correctly operating RCD is that you should not reach the "can't let go threshold" before the RCD trips

frank

dorian · Guru

According to Wikipedia, the "let go threshold" is 10mA.

http://en.wikipedia.org/wiki/Electric_shock

"At around 10 milliamperes, AC current passing through the arm of a 68 kg (150 lb) human can cause powerful muscle contractions; the victim is unable to voluntarily control muscles and cannot release an electrified object. This is known as the 'let go threshold' and is a criterion for shock hazard in electrical regulations."

-- Edited by dorian on Saturday 4th of January 2014 11:58:12 AM

oldtrack123 · Guru

removed Double post

-- Edited by oldtrack123 on Saturday 4th of January 2014 12:13:08 PM

oldtrack123 · Guru

dorian wrote:
According to Wikipedia, the "let go threshold" is 10mA.
http://en.wikipedia.org/wiki/Electric_shock
"At around 10 milliamperes, AC current passing through the arm of a 68 kg (150 lb) human can cause powerful muscle contractions; the victim is unable to voluntarily control muscles and cannot release an electrified object. This is known as the 'let go threshold' and is a criterion for shock hazard in electrical regulations."

-- Edited by dorian on Saturday 4th of January 2014 11:58:12 AM

Hi

They are available in a range of trip threshholds 10mA up to 100mA

Theyalso have a specfied time /current curve in which they SHALL trip

The size to be used depends on the situation ,

But Threshold is not the only thing that determines TYPE

The TYPE of AC power also has an effect & can determine TYPE

This is especially true if fitting to inverters or generators

Knowing what the CORRECT TYPE & TRIP rating for a specific situation is essential

PeterQ

-- Edited by oldtrack123 on Saturday 4th of January 2014 12:16:39 PM

-- Edited by oldtrack123 on Saturday 4th of January 2014 12:20:43 PM

Ontos45 · Guru

brian wrote:
Ontos45 wrote:
I sometimes wonder how we are all still alive! People have been using 240VAC power in vans long before the powers that be decreed RCD's compulsory and how many of us just earthed the generator, connected it up to van and away we went. Not saying that the advances aren't beneficial but it seems a bit over-board sometimes, not only in this field but others too. Just a thought.
You are absolutely correct.
Many of us also drove cars before seat belts became the norm, and survived.
Do you still do that?
Many of us smoked before the risks became well publicised, do you still do that?
Are the compulsory wearing of seat belts and other personal health concerns that have been recognised and safeguards implemented also overboard?
All of us are quite at liberty to ignore the safety warnings at our own risk.
At the very least, do it with full recognition of the possible dangers into which you may place yourself and others, and be willing and able to face the consequences of such action, which may just possibly be the loss of your life, or worse still, that of a loved one.
Many very smart people with many years of experience and access to all of the data relating to electrical accidents have pooled their knowledge to produce safety equipment and rules to limit the dangers involved with using electricity.
Why ignore that?
Make a mistake with your plumbing and you might get wet, make a mistake with electricity and you might get dead.

I, the same as all of us, started wearing seat belts because their wearing became law. I said it was a "thought", I did not disagree with you. In a club, GN, this size there are many of us who are conversant in a threads subject but stay silent because it's being handled quiet well and correctly by others. We just sit back, sip our beer and, sometimes, shake our heads, as we just learnt something new.

Ex. member of the ETU, left 1980.

KFT · Guru

Hi Dorian

Which is why medical and dental treatment areas are required to be fitted with 10mA RCD's OR isolated supplies depending on the type of procedure carried out within that area.

I consider it most unlikely that the fault current would remain stable but would rapidly climb to the trip point of the RCD.

These values are arrived at by calculation based on the human bodies impedance assessed as being 1000 ohms approx.(determined by the IEC). At 230v this would mean a current of 230mA which will trip the RCD.

When RCD's are tested in medical facilities the trip time must be under 40 milliseconds.

a person would not unaffected BUT THEY VERY LIKELY WOULD BE ALIVE.

frank

-- Edited by KFT on Saturday 4th of January 2014 12:33:45 PM

brian · Guru

Ontos45 wrote:

I, the same as all of us, started wearing seat belts because their wearing became law.

Not all of us !!!

I fitted lap belts (combination lap-sash were not then available) to my EK Holden back in 1964. At that time, it was quite obvious by testing being carried out, that seat belts had much upside and little downside.

My next car, a VC Valiant had lap belt mounts only but it was an easy job to fit lap/sash ones which I did in 1968.

Compulsory wearing of belts was not introduced until the early 70s by which time I, and I suspect many others, had been using them religiously for almost a decade.

Smoking is still legal, is it only the cost that has caused many people to refrain?

Some people don't require legislation to force them to make smart decisions.

Ontos45 · Guru

brian wrote:
Some people don't require legislation to force them to make smart decisions.

Pity they are in the minority when it comes to some things isn't it? Some people think because they can buy a GPO or 3 pin plug in their local Tom Dick & Harry store it's OK to wire them up. Maybe that should go the same way as drug smoking utensils are illegal for sale (at least in Qld.). Remember CAMS required 4 point seat harnesses long before civilian vehicles where required to have seat belts.

Back to my beer.

oldtrack123 · Guru

HI Brian

But unfortunately there will always be some who will fight to the last against common sense

Or whinge about "nanny state regulations

Standards excuse /reason

"It's never happened to me"

To whom I suggest

TOMOROW MAY BE THE DAY!!!

PeterQ

dorian · Guru

KFT wrote:
I consider it most unlikely that the fault current would remain stable but would rapidly climb to the trip point of the RCD.

These values are arrived at by calculation based on the human bodies impedance assessed as being 1000 ohms approx.(determined by the IEC). At 230v this would mean a current of 230mA which will trip the RCD.

I have measured leakage resistances in several appliances, including a breadmaker, a clothes washer, dishwasher, and refrigerator, but only the refrigerator had a direct short, and that short was between earth and neutral, IIRC. The fault in the latter only became evident when the appliance was replaced. It had been working fine until that time, on an unprotected circuit. When we plugged it into a protected circuit, it tripped the ELCB. The other appliances had leakage resistances of several kilohms, probably due to water. In fact, I dismantled the breadmaker to locate the source of the leakage, but it went away before I could find it.

I can't imagine a real scenario where the leakage current would remain stable, but if you were to find a 10K fixed resistance between yourself and the 230V supply, then that would easily result in around 20mA of fault current. That resistance figure is within the ballpark of those that I actually encountered.

KFT · Guru

Dorian,

when we were doing acceptance tests on new equipment prior to it entering service the test instrument would often indicate some earth leakage. As long as the measured value was below 6mA it was accepted, anything in excess of that the equipment was rejected.

you are already aware that appliances with heating elements do require some dehumidification in order to pass a test when new so in that scenario the leakage could be in the region of what you state but I would expect that leakage to reduce as the insulation resistance rises.

frank

oldtrack123 · Guru

HI Dorian
As a result of that fridge, you are no doubt aware that A RCD will react to a neutral to earth fault /leakage DOWN STREAM from it
,

That can happen even if the leaky device is not switched on
[in domestic situatiions]

Exceeding the let go threshhold itself does not mean electrocution

A time factor is also involved

ie A Healthy person can usually withstand 30mA for 40 msec without serious harm

Even much higher currents may not electrocute l

RCDs are available with time ranges up to 500mS

PeterQ..

-- Edited by oldtrack123 on Saturday 4th of January 2014 02:53:53 PM

-- Edited by oldtrack123 on Saturday 4th of January 2014 03:10:31 PM

-- Edited by oldtrack123 on Saturday 4th of January 2014 03:16:51 PM

Ontos45 · Guru

Have copied this from an Explore Oz forum on same topic in 2010.......suggestions?

NEW Product for elecrtical safety

Submitted: Friday, Jun 04, 2010 at 20:41

oldtrack123

HI All
The below post by permission of Krusty of C& H forum:

""For those interested in the next step in electrical safety, there is about to be launched into the market a replacement for those Clipsal orange box extension outlets; these are the ones specifically disallowed under the present regs for RVs.

The little cheap white power boards (supercheap, reject shop, bunnings etc) always have been suggested as poor substitutes for real wiring and they never have been suitable for the RV (especially camping) market. The Clipsal product is marketed as suitable for the construction industry (building sites) but it is not suitable in camp sites (van/motor home/tent).

A multi-outlet power board has been legally required (multi buildings on a single site) for some time but accessing them has been a problem as they need to be individually made up.

There has also been a problem with plugging a 15 amps caravan into the normal 10 amps domestic gpo (we are all aware of the cheater plugs).

The new unit is to be marketed as a power board with combined RCD & RVD functions, where the resistance to earth is less than 1 kilo Ohm the RCD has been tested to function with the present 30milliamps limit. When the resistance to earth is over 2 kilo Ohms the RVD has been tested to function with a lower limit.

The human body has a nominal resistance @ 1.5 kilo Ohms and at this range (per reports) either the RCD or RVD will function giving a double protection. I have not seen the circuit but the device is about to be certified.

I have suggested to the manufacturers that a version be made with a 10amps plug suitable for plugging into a domestic house with a 15 amps output that will accept a standard caravan lead. They are likely to also make the 10 to 10 version and the 15 to 15 version. The suggested price is around $200 (twice the price of a Clipsal but double the protection & legal); it is also less than the amp fibian 10 to 15 amps convertor.

The advantage with the device is that when at home you will be legally covered for plugging your van into your home powerpoint. When on the road by plugging the device into either your invertor or generator multiple class one devices may be driven off of it concurrently.

Present advice is 1 class one device per outlet and the caravan itself is a class one device and should therefore NOT supply any other building within the same site. (As is done at caravan shows).)."""

For more info on these products contact via this link

www.protectelec.com.au/display/assets/download.php

I nor Krusty have no connection or finincial interest in the company but see these products as a great step forward in the safe use of portable gennys & inverters

Peter

(I think it's called a "Protex RVD".........more on this at...... peter)

http://caravanersforum.com/viewtopic.php?f=2&t=8782

-- Edited by Ontos45 on Monday 6th of January 2014 12:03:15 PM

-- Edited by Ontos45 on Monday 6th of January 2014 12:18:39 PM

Ontos45 · Guru

Also found this on "earthing for 240VAC on trailers.

the new Universal RCD comprising a Double pole RCD and the Protex IFS acts as a dual system and is approved by the NSW Regulator with the Number NSW24815.
The IFs is in a Shunt Trip case and when on mains power if the power supply plugged in is reverse pole the IFS trips both the IFS and the RCD out as it will not allow reverse pole power.
Then if the mains power is correct pole the IFS will sleep and let the RCBO do the job it is supposed to do within 30Ms if a fault occurs.
If you switch to generator and or inverter and plug into the RV inlet and a fault occurs the IFS acts in 5Ms and also trips the RCD and without the IFS the RCD will not activate as there is no earth reference.
So the combined RCBO/IFS can replace the current RCBO used in all RV applications and give total safety whether by mains MEN or Isolated Inverter/Generator.
That is with an Inverter capable of full supply and where an inverter is stand alone then the Protex RVD can be installed in the Inverter to safeguard the output from fault.

With thanks to:

www.myswag.org/index.php

oldtrack123 · Guru

Hi Chris

Actually there are now several models available fordifferent applications

The original version has been suiperceded, but the basic principles are the same

So care is required in making the right choice

,ANYONE using a generator OR inverter plugged into the VAN power inlet should replace the RCD with one of these units

AT this point in time, they are ,IMHO, the best possible protection availablei

There is currently no otherr unit in place of the AMpfibian for 10to 15A conversions

ps there are moves afoot for some other useful products based on,, these units but not finalised as yet

A search for " RVDs" on most RV/ caravan forums will bring up further informtion

Including some from Ian of Powerstram

PeterQ

-- Edited by oldtrack123 on Monday 6th of January 2014 12:49:57 PM

-- Edited by oldtrack123 on Monday 6th of January 2014 01:00:05 PM