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#110014 - 01/10/06 07:48 AM More creative "Choc Block" Madness (UK)  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Quote
You may remember some time ago I sent some pictures of lighting in an office suspended ceiling. This is more of the same guys work. It is still in regular service and it runs on 200V 3 phase 300Hz for grinders. It was spotted by one of my contractors.

- Johno12345


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#110015 - 01/10/06 07:53 AM Re: More creative "Choc Block" Madness (UK)  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Quote
it runs on 200V 3 phase 300Hz


There's got to be some kind of interesting explanation behind that weird specification!

[Linked Image]


#110016 - 01/10/06 08:29 AM Re: More creative "Choc Block" Madness (UK)  
IanR  Offline
Member
Joined: Dec 2004
Posts: 328
Palm Bay FL USA
At that frequency, the grinder motors would really be hauling. But 300 is a wierd value to settle on. Maybe 400 Hz was too fast?


#110017 - 01/10/06 09:25 AM Re: More creative "Choc Block" Madness (UK)  
johno12345  Offline
Member
Joined: Sep 2005
Posts: 96
United Kingdom
Hi,

I have been told that the frequency was chosen to reduce vibration white finger. No one is old enough to remember when it was installed but it has a rotary frequency convertor connected to it which burned out, that is what caused us to notice it.
The box with the contactor contains the motor starter. The grinders plug in using some bizarre metal socket with a metal sprung lid.
No one knows what happens to that SY cable. I shudder to think [Linked Image]
In the last pic, the earth has been disconnected. When it was re-connected, the breaker wouldnt stay on. That has all been re-wired since, we didnt even bother to find a fault.


I took my time, I hurried up, The choice was mine, I didn't think enough

#110018 - 01/11/06 12:36 AM Re: More creative "Choc Block" Madness (UK)  
JoeTestingEngr  Offline
Member
Joined: Nov 2005
Posts: 785
Chicago, Il.
Is that a contactor installed on the door in the one pic?(with the hanging connectors) That looks pretty scary to me. So what did you do? Convert to more conventional wiring techniques with VFD(s)?
Joe

[This message has been edited by JoeTestingEngr (edited 01-10-2006).]


#110019 - 01/11/06 05:48 AM Re: More creative "Choc Block" Madness (UK)  
johno12345  Offline
Member
Joined: Sep 2005
Posts: 96
United Kingdom
That on the door is the on/off switch for the voltage/frequency set, there is a start and stop button on the door to. I will try and get a pic of that later. It is a mechanical one. It is still in use today, with no plan to upgrade it - "if it works, it must be ok" thats our motto. I work in IT so dont get directly involved with that side of maintenance.


I took my time, I hurried up, The choice was mine, I didn't think enough


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