Re: 3 phase (was LF: G3KEV)

[Andy Talbot <andy.g4jnt@gmail.com>]

Back in my student days, I once spent time at a place that did final tests on a missile launcher system that had 400Hz motors.   One test was phase rotation of the supply.  The chap in charge didn't like the long winded test procedure proscribed (I don't know what it was, he never used it)  so he'd made himself a network in a tobacco tin (yes, truly) using CR phase shifter network and neon bulbs.

It worked easily and quickly, lighting one neon or the other depending on rotation

'jnt

On 28 November 2015 at 17:18, Markus Vester <markusvester@aol.com> wrote:

I've been wondering if there exists a screwdriver-like handheld voltage tester which can identify a 3-phase sequence, without physical connection to the "other" phases.  Using an internal crystal reference, such a device could measure line frequency and phase while touching the first point, and then remember the phase state while being taken to the next one. Depending on line frequency drift rate you may have to be quick, but I think it could be practical. 

 

Best 73,

Markus  (DF6NM)

 

-----Ursprüngliche Mitteilung-----
Von: Andy Talbot <andy.g4jnt@gmail.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Sa, 28 Nov 2015 5:29 pm
Betreff: Re: 3 phase (was LF: G3KEV)

What's wrong with that ?

Sounds an excellent idea for a QRO transmitter.   300Hz ripple - much easier to filter out.

My 137kHz Tx runs from rectified (single phase) mains - the isolation is provided in the ferrite output transformer and FET drive pot-core

A school we once went around with long leads and an AVO  identifying sockets to be found on all three of the phases.  That was so that, using extension leads, we could bring them all into the lab to get a three phase motor running.   Such interesting things could be done in schools in the 1970's

Andy G4JNT

On 28 November 2015 at 15:52, John Rabson <john.rabson07@gmail.com> wrote:

In the early days of 73 kHz I believe a Luxembourg station built a transmitter which was powered off full-wave rectified three-phase mains without an isolating transformer. NOT the best way of doing things!

John F5VLF