Re: 3 phase (was LF: G3KEV)

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

If you use two transformers on a 3-phase supply, with the primary windings in a SQRT(3) ratio, one connected in delta, and one in star across the supply; equal value secondaries when rectified will give you 12X ripple instead of the 6X normal achieved though full wave 3-Ph rectification.

Unfortunately SQRT(3) is not rational (becuz Euclid sez so!) so any turns ratios will be approximate, hence ripple will be degraded marginally

'jnt

On 28 November 2015 at 18:20, mal hamilton <g3kevmal@talktalk.net> wrote:

Andy es Co

6 phase even better lower ripple.

A car alternator is 3 phase, could easily be 6

g3kev

 

 

 

From: Andy Talbot

Sent: Saturday, November 28, 2015 4:26 PM

To: rsgb_lf_group@blacksheep.org

Subject: 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