has anyone seen eddy current in action?

[einstein]

Any good storys?

 

[Andy78]

Never in work.
Saw a video of a recycling sorter once that uses eddy currents to push ferrous items off a conveyor belt.

 

[Andy78]

Oh, and I'd like to nominate my last post for "most interesting post" in the annual forum awards.

 

[Pete999]

Any good storys?

Oopps sorry my mistake

 

[Jay Sparks]

Seen these. I think they are a tribute band.

Sorry....

 

[static zap]

When I wer t youngun , they made flat disks of alumunium spin .
(or jump when you blew a fuse )


(Balanced wiring --metal boxes again...hmmmm)

 

[Darkwood]

I got called out to conduits getting hot after a firm moved into a new build, it turned out the electricians had run the 3phase to the switch bank for the lighting through 3 conduits and lost the cancel out effect, the conduits were that hot we couldn't hold them, the MCB's had been tripping is the original call out and when they corrected their design problem they had just replaced the metal with plastic.. the issue still effected further upstream... they didn't like a 21yr old telling them there design was to blame especially looking 5yrs younger than my real age, after lot of blame and shame from them they rectified the install to how I suggested and walked away tail tucked between their legs.

 

[marconi]

.eddy current poem - Google Search - https://www.google.co.uk/search?q=eddy+current+poem&tbm=isch&source=iu&pf=m&ictx=1&fir=qhu6yBtMSmZA-M%253A%252CJiBybdP3A5qFIM%252C_&usg=__osnCqY6ge8myheoWBtWGZieIJFE%3D&sa=X&ved=0ahUKEwj6zcK6joHXAhXC2BoKHWhHCnQQ9QEIPDAF#imgrc=qhu6yBtMSmZA-M:

 

[Deleted member 9648]

Here's one I spotted recently, 100a rotary isolator, 25mm tails, completed by an ELECSA AC in 2011. Nice.

 

[Deleted member 93172]

Here's one I spotted recently, 100a rotary isolator, 25mm tails, completed by an ELECSA AC in 2011. Nice.
View attachment 38924

You can't believe it can you, in all my years of sparkying things like this amaze me, the installer must have had the day off from tech(if he went at all) when this subject was taught. Why not just use a large male bush and locknut ? or if you must do it like the picture,put a slot between the knockouts with a jigsaw, to create in theory one hole.

 

[Bobster]

I got called out to conduits getting hot after a firm moved into a new build, it turned out the electricians had run the 3phase to the switch bank for the lighting through 3 conduits and lost the cancel out effect, the conduits were that hot we couldn't hold them, the MCB's had been tripping is the original call out and when they corrected their design problem they had just replaced the metal with plastic.. the issue still effected further upstream... they didn't like a 21yr old telling them there design was to blame especially looking 5yrs younger than my real age, after lot of blame and shame from them they rectified the install to how I suggested and walked away tail tucked between their legs.

Really? A lighting circuit causing what I'm presuming to be 20mm galv conduit to get that hot? What did they have, 50kW of lighting on each phase?

I've seen a temperature rise of a few degrees whilst playing in the workshop at low current. (low current in this case was (16 - 32A) To get anything to where I couldn't hold the metal it was >150A.

 

[Darkwood]

Really? A lighting circuit causing what I'm presuming to be 20mm galv conduit to get that hot? What did they have, 50kW of lighting on each phase?

I've seen a temperature rise of a few degrees whilst playing in the workshop at low current. (low current in this case was (16 - 32A) To get anything to where I couldn't hold the metal it was >150A.

It was a poor design throughout, factory of inductive lighting run through into a 12gang grid (no contactors) if I recall, mixing phase entries up on high inductive loads was probably a key factor plus across several lighting circuits over the phases, hard to repeat on a bench I would imagine.

 

[Darkwood]

@Rob... remember that once the temperature rise goes past the temp dissipation line the run away effect can turn a couple of degrees rise into a furnace over a long period.

 

[marconi]

Could the high temperature of the conduit have been caused by the Ohmic heating of bundles of conductors contained inside the metal conduit whose size was inadequate for their current flow, containment, ambient temperature and demand factor? Maybe several IsquaredRs proved more troublesome than eddy current heating in this instance.

 

[Darkwood]

Could the high temperature of the conduit have been caused by the Ohmic heating of bundles of conductors contained inside the metal conduit whose size was inadequate for their current flow, containment, ambient temperature and demand factor? Maybe several IsquaredRs proved more troublesome than eddy current heating in this instance.

No as my rectification cured it after they tried to, it did not involve grouping factors, cable sizing etc as this still existed in other conduits downstream that were not effected, I work with motors a lot and VSD control, I have a good understanding of what can occur when you run the motors too slow through speed control and the impeller can no longer dissipate the motors normal heat generation, it can melt high temp' winding insulation off and it happens due to the runaway effect that could initially be a few degrees over its dissipation capability due to the slower impeller speed, you do not need any initial high temperature, you just need a degree or 2 more that it can remove naturally and the runaway effect can end up cooking the install.

 

[sweet212]

A few years ago as an apprentice the firm I was working for replaced a switch panel feeding a leisure centre. The on site transformer fed a 3P ACB that then fed the panel. I cant remeber the amperages but I remeber the tails were 500mm in parallel. The cables ran along ladder racking before diving into the switch panel. The cables were dropped through the ladder racking in such a way that when initially energised within minutes the racking was red hot.

I remeber one of the lads walking in with a reciprocating saw saying he would fix it.

Great job working nights with good blokes. Those were the biggest cables Ive worked with.

James

 

[jamie-spark]

Found this the other day

Phone up by the concerned customer as the trunking lid was vibrating

 

[Marvo]

I think in general domestic and light commercial installations you're unlikely to see any spectacular effects due to eddy currents. Even in a case of severe disregard like in the photo above, where every final circuit has its live and neutral conductors through different entry hole, whilst the DB cover may buzz you're unlikely to cause sufficient heat to do any damage.

 

[ian.settle1]

Here is some

 

[Pete999]

Saw Eddie Kidd once, yes on a bus bar riser very scary