Random thought - Level 3 EAL.

[Dave Rudderham]

So I'm well on the way to completing the second practical assessment in the EAL L3 EI course. Me being me, and the tutor saying "We don't normally switch the neutral in the UK" I decided (with permission) to adapt the assessment and move the neutral conductor out to the DIN rail.
I've drawn out the diagram with the minor alteration. As I followed the current path I noticed something that seemed not to sit right with my mind.

Why on earth does the Line conductor come in on 1, feed through the contactor out on 2, feed back to 3, through the contactor again and come out on 4 to the "motor" feed. Why go through the contactor twice? Is this a normal procedure on a single phase motor control, or has someone made an error. To pass through a second set of contacts like this doesn't register with me, it doesn't appear to have anything to do with the overload unit. Am I missing something?

Please excuse my crude diagram.

 

[telectrix]

the L goes through the stop/start circuit and the aux. contact ( hold in) and feeds the coil

 

[static zap]

Clue .Think inductive load getting disconnected!
(Contacts come for free - less wear)

 

[Dave Rudderham]

the L goes through the stop/start circuit and the aux. contact ( hold in) and feeds the coil

Is that not what 13/14 is for?

 

[Dave Rudderham]

Clue .Think inductive load getting disconnected!
(Contacts come for free - less wear)

Ahhhhh..... Gotcha

 

[static zap]

Thats normal operation covered ... now is there a worst case !
(Belt and braces )

 

[static zap]

Please excuse my crude diagram.

..as Telectrix notes ..there is a problem .

 

[Dave Rudderham]

..as Telectrix notes ..there is a problem .

Ah, I see what I did. Was on a phone when I answered earlier and it didn't appear clearly. Hopefully that should correct the diagram.

 

[static zap]

(was a bit of confusion -AUX contacts on same contactor -vs- seperate overload section ) ..labeling

 

[Dave Rudderham]

(was a bit of confusion -AUX contacts on same contactor -vs- seperate overload section ) ..labeling

I'll try and scan the copy the college gave us, it's even worse!

 

[static zap]

This is just a quick schetch , so long as document explains it 2 parts , probably not a problem for clarity.
(Follow the brown wire game !)

 

[static zap]

Think may be broken ,now - will look again ,power from stop , straight to coil , missing start ?
(both START and 13-14 in parallel = good)
(was ok before - perfect layout takes time )