What's on your Ctrl+V?

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Instead of UNWINDING turns to reduce the voltage you could ADD some turns! Two options here. The idea here is to add a winding or two that can be hooked in series with one (primary) or two windings (sec) that will be out of phase and 'buck' the voltage produced by the existing windings. This is akin to placing a separate transformer in series with the primary winding of an existing transformer to effectively reduce or increase the voltage applied to the main transformer to correct for line voltage sag, etc.

You will have to determine how many volts per turn your torroid makes as is. To do this wind say ten turns of scrap hookup wire, guage not important for this test around the core of the toroid and hook up a AC voltmeter. Energize the primary winding as normal. You should see a voltage developed which will usually be less than a volt per turn on a transformer of this size. Perhaps 1/4-1/2 volt. This is the number you use to determine how many turns you need to add if you want to buck the primary, or buck each secondary winding with its own separate bucking coil.

For example if you want to add turns to buck the primary (in this case probably the easiest solution). Your desire is to drop the secondary from 40 volts to 35. 35 volts is 87.5% of 40 so you need to make the new input voltage to the primary 87.5% of nameplate voltage. If the mains voltage is 115 volts then this amounts 14.4 volts drop to 100.6 volts. If your test indicates that you get exactly half a volt per turn from this core then it is a matter of 14.4 volts divided by 0.5 volts = 28.8 turns, That should be easy to do by hand. Use a suitable gauge magnet wire to carry 300 VA. #18 or #20 AWG ought to do it. You can use plastic sleeved wire instead of enamelled magnet wire if you wish. Hooked in series one wat with the primary will give the proper output voltages you desire. Hooked up the other way (wrong) will give you an increase in output voltage.

This is an easy and virtually free fix to your problem.
 
______________________________________________
From: ******************
Sent: 04 December 2009 09:03
To: R ICT Helpdesk General
Subject: RE: USB port access

************ heads up ****** she currently has a port open on a computer at Hemel but is now required to work out of Watford on occasions and requires the same there.

**********

_____________________________________________
From: R ICT Helpdesk General
Sent: 04 December 2009 08:49
To: ****************
Subject: RE: USB port access

Hi *************

Please could you advise us of the use of the USB port?

Regards

Helpdesk

_____________________________________________
From: ******************
Sent: 03 December 2009 17:14
To: R ICT Helpdesk General
Subject: USB port access

Please can the USB port on C1SU5 (socket 2/07) based at Watford ( to be used by Inspector Spencer 545) be made available for use. This computer sits in an office where one other Inspector works on the 2nd floor of the admin block

Many thanks

*************
Customer Service and Business Support Manager
Hertfordshire Constabulary (Western Area)
Tel: ****************



Starred for obvious reasons, really not very exciting...
 
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