we used to call them earth leakage circuit breakers
Socket failure??
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But not a VO ELCB.
yes but there were current operated too, which are rcd/gfci
But not a VO ELCB.
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But not a VO ELCB.
VO ELCB are current operated. The impedance of the coil that trips the mechanism is selected so that when the current passing through the coil to Ground reaches tripping point then the voltage across the coil is equal or less than the voltage quoted as being the trip voltage.
An electroscope is a genuine voltage operated device but it is far from able to create enough mechanical force to trip a mechanism
Is it?
I may be wrong, but I thought that any movement in an electroscope was due to the build up of a charge, relating to Coulomb's law.
...and an electrical current is the movement of charged particles?
The the two leafs in the electroscope both acquire the same potential from an extremely small current.
Electrons are very anti-social and do all they can to get away from any other electrons, this results in the electrons on the leafs forcing the two leafs apart.
( I think that is how the school physics master explained the matter ).
Electrons are very anti-social and do all they can to get away from any other electrons, this results in the electrons on the leafs forcing the two leafs apart.
( I think that is how the school physics master explained the matter ).
What did the English master say about it?
Yes, hence my point.
For the leaf to move, there must be a difference in charge and a flow of current.
A potential difference alone, would not be enough to create the work to move the leaf.
You could possibly say that, but without the movement of charged particles, it wouldn't be very useful; the leaf being stuck in the same position!
a current operated ELCB was, in effect, an RCD. A voltage operated ELCB was, in effect, a voltage comparator
perhaps the terms VO and CO are unfortunate because in both cases a relay/solenoid needs a current to flow thru it to trip it and thereby a voltage across it. however one is effectively comparing currents and the other one is comparing voltages. much in the same way a bog standard multimeter measures effectively measures the same thing when we use it to deduce amps/ohms/volts
perhaps the terms VO and CO are unfortunate because in both cases a relay/solenoid needs a current to flow thru it to trip it and thereby a voltage across it. however one is effectively comparing currents and the other one is comparing voltages. much in the same way a bog standard multimeter measures effectively measures the same thing when we use it to deduce amps/ohms/volts
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We're (Bernard's) talking semantics - all electrical devices (including electroscopes
) require current to operate. Without the movement of charged particles, a voltage alone wouldn't be able to do very much!
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Bernard, there were two versions oF ELCB on the go into the 70s. one was voltage operated and the other was current operated. we abandoned the VO ones and continued with the CO ones and a bit later on renamed them RCDs.
to call them VO or CO might actually be a misnomer but it was a way to distinguish the two different types. the VO ones had more drawbacks so CO ones won the day.
in fact there is a diagram on the web to show an RCD effectively configured to become a loss of PEN device (by virtue of becoming VO) and disconnect our PEN to avoid danger, although not legal here.
to call them VO or CO might actually be a misnomer but it was a way to distinguish the two different types. the VO ones had more drawbacks so CO ones won the day.
in fact there is a diagram on the web to show an RCD effectively configured to become a loss of PEN device (by virtue of becoming VO) and disconnect our PEN to avoid danger, although not legal here.
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The VO was designed to operate when the voltage difference ( delta V ) between Ground potential ( from a Ground Rod to Terminal E ) and the potential on the internal Earth ( connected to Terminal F ) was greater than 50 volts ( other voltages were available ).
Simple concept that prevented the safety Earth ( CPC ) inside the building from becoming Live. Worked fine provided there were no alternative paths from CPC to Ground, even then it did prevent the delta V becoming dangerously high should some one be in contact with the CPC and Ground at the same time.
Metallic water mains that were bonded to the CPC were the most common alternative path, In a fault situation several Amps ( if not tens of Amps ) could flow through the alternative path without raising delta V to a voltage high enough to trip the VO ELCB Significant, possibly dangerously high, earth leakage but the ELCB would not be tripped.
Simple concept that prevented the safety Earth ( CPC ) inside the building from becoming Live. Worked fine provided there were no alternative paths from CPC to Ground, even then it did prevent the delta V becoming dangerously high should some one be in contact with the CPC and Ground at the same time.
Metallic water mains that were bonded to the CPC were the most common alternative path, In a fault situation several Amps ( if not tens of Amps ) could flow through the alternative path without raising delta V to a voltage high enough to trip the VO ELCB Significant, possibly dangerously high, earth leakage but the ELCB would not be tripped.
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