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Member postings for David Thomas 6

Here is a list of all the postings David Thomas 6 has made in our forums. Click on a thread name to jump to the thread.

Thread: Index to Issues of MEW ?
04/08/2009 11:11:35
Thank you.
 
In case anyone is interested, the files (which are Excel or "Comma Separated") import beautifully into Bento, a database application for Apple. That allows full searching and reordering by any aspect of the indices.
Thread: Phase Converter Which Type?
04/08/2009 10:48:46
.... oh, and here's a sketch of the control wiring required. Use at your own discretion and risk.
 

 

Edited By David Thomas 6 on 04/08/2009 10:50:34

04/08/2009 09:50:13
I have experience of Inverters/VFDs in a home workshop, but not the static and rotary converters.
 
The VFD (my two are Parker SSD models) is great: quiet, flexible, small and neat, and I think very safe. It provides soft start, no-volt stop and flexible speed control.
 
However:
- with a 240V supply, you will only get 240V 3-phase and (as John says) will need a VFD sized to output 11 amps. (The good news is that the soft start controls inrush current, and you don't need to cater for a momentary 60 or 80 amps at start)
- you will need to buy or make a control box which replaces the existing push buttons on the mill, and is permanently wired into the inverter.  I made mine from components I got from RS, and the total cost was £50-60 for On, Stop, Jog and Reverse pushes and switches, contact blocks, potentiometer, enclosure etc : in addition to the cost of the inverter itself
- the inverter must have an EMC filter (radio intereference) fitted and must be wired carefully using screened cables, because it works by creating phase differences and a side-effect is electrical 'noise'
- for the same reason, you will need to plug it into a circuit which is protected by circuit breaker (MCB) but not a residual current device (RCD), because the inverter creates earth leakage (or it may just be a sort of phantom earth leakage because that's what the phase difference 'looks like' to the equipment, I'm not sure). Whatever it is, it will trip an ordinary domestic RCD.  I am not an electrician, but I suspect the latest wiring regulations require any NEW sockets to be RCD protected, so whether this creates a problem depends on your wiring and circumstances.
- the latest MEW contains an article about converting a 3HP Harrison lathe to inverter drive, and suggests that there is a correct way to install the power supply under the latest regulations: I think the author understands the details better than I do.
 
Thread: Index to Issues of MEW ?
04/08/2009 08:42:19
Is there, please, an index file to all MEW that could be downloadable from the site ?
 
If not, how does one obtain an index ?  I have printed ones going back to Issue 106 (I think) but not earlier.
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