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-   -   Is it a world record? (http://www.plctalk.net/qanda/showthread.php?t=113253)

Ronnie Sullivan December 6th, 2017 04:19 PM

Is it a world record?
 
7, 3 phase motors connected consecutively - all wrong direction.

They were wired in plain black wire (to be marked when connected)
And I was doing the panel end and another man doing the motor ends with no belling out.

I call the record at 7 :)

the_msp December 6th, 2017 04:33 PM

You have a 50% chance of getting it right... and a 90% chance of getting it wrong...

AustralIan December 6th, 2017 04:38 PM

That should happen every 128 times you do that, on average.

Bering C Sparky December 6th, 2017 04:46 PM

They certainly seem to be backward more than they correct for sure......but 7 in a row....you should buy a lotto ticket, maybe your luck is due for a change about now.

BCS

Ronnie Sullivan December 6th, 2017 04:54 PM

Someone said the exact same thing (lotto ticket)

I have had theory for years about motor direction.
If it is awkward or tight for room to change the wires, they will be wrong.
In the panel they were in the bottom terminals with about 50mm of room. I had to lay on my side using long nosed pliers to get them in

jraef December 6th, 2017 06:36 PM

Quote:

Originally Posted by Ronnie Sullivan (Post 761317)
Someone said the exact same thing (lotto ticket)

I have had theory for years about motor direction.
If it is awkward or tight for room to change the wires, they will be wrong.
In the panel they were in the bottom terminals with about 50mm of room. I had to lay on my side using long nosed pliers to get them in

Also, if there is an entire room full of VIPs watching you hook it up to see the new equipment run, the direction will be wrong and no matter how many times you explain that there is no simple way to tell in advance, you will still be the goat...

7 in a row though... that does beat my record of 5, on a machine that had 5 motors on it.

Aabeck December 6th, 2017 07:14 PM

When I install a line with many motors not VFD controlled I check the rotations and if the majority need reversed I reverse the incoming feed.

I had one customer that insisted the incoming feed had to be a certain rotation and I had to reverse almost 30 of the 35 motors on the line.

Dirt December 6th, 2017 07:20 PM

Well, even if you wire up all motors "correctly" but someone mixes the feeding phases somewhere.. Have had that happened before.

GaryS December 6th, 2017 07:56 PM

try one of these
http://www.aemc.com/products/html/mi...bname=products

they solve the motor rotation problem

Dirt December 7th, 2017 12:58 AM

1 Attachment(s)
Sometimes they even get the outgoing lines from a 650MW generator in the wrong order..
Attachment 46307

GaryS December 7th, 2017 02:13 AM

That must be from across the pond
Here is in the US large stations are all connected to the grid. There is a predefined sequence to the grid network. We don’t cross the wire over like that we sequencronise the generator to the line so everything always match. They constantly monitor it, if it get out by 1/2 hz they open the switch and isolate the generator otherwise it would take the grid down. Look at the great northeast blackout in mid 80's took a big chunk of the grid out due to 1 generator fault. Left most of the North East in the dark they didn't isolate it soon enough they learned their lesson and isolate them faster now.

Rob... December 7th, 2017 02:13 AM

There's a good proportion of Englands distribution network that is the opposite rotation to the rest of the country.

A **** up that was made around the WW2 era, an now would simply cost to much to correct.

GaryS December 7th, 2017 02:34 AM

By the way I just had to through this out there
Most of the UK power is generated and disturbed. By PPL UK a homely owned company of PPL Global an US Base company headquartered here in Pennsylvania
That's probably the part that stays working

Saffa December 7th, 2017 03:48 AM

Quote:

Originally Posted by GaryS (Post 761368)
By the way I just had to through this out there
Most of the UK power is generated and disturbed. By PPL UK a homely owned company of PPL Global an US Base company headquartered here in Pennsylvania
That's probably the part that stays working

I'm surprised anything works properly in the good ol US of A what with only 110VAC and that crazy imperial system.

Dirt December 7th, 2017 05:21 AM

Quote:

Originally Posted by GaryS (Post 761365)
That must be from across the pond
Here is in the US large stations are all connected to the grid. There is a predefined sequence to the grid network. We don’t cross the wire over like that we sequencronise the generator to the line so everything always match. They constantly monitor it, if it get out by 1/2 hz they open the switch and isolate the generator otherwise it would take the grid down. Look at the great northeast blackout in mid 80's took a big chunk of the grid out due to 1 generator fault. Left most of the North East in the dark they didn't isolate it soon enough they learned their lesson and isolate them faster now.

Well you can't syncronize two phases swapped? Unless you can turn the rotor current in the opposite direction. I do not know the whole story from back in the day, this happened more than a decade before I was born.

Somewhere around 1/2Hz off will trip on my side of the pond as well. Of course this one is connected to the grid, like a large generator in the US.

This was a design fault made in the early 70s.. The grid is supposed to be one certain way (and is), like on your side of the pond. The problem here was that the designer of generator/breaker didn't take into account that it gets "mirrored" looking from one side compared from the other.

This is a very unique solution here, I haven't seen it anywhere else.


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