Loss of one electricity phase causes low voltage (95 V) for everyone

DC? I suppose a simple 4-diode bridge rectifier (the input between the mains and the step-down transformer) will pass DC no matter what the polarity is, and if the step-down transformer is *after* the switching circuit (making the transformer much smaller) then DC will reach the oscillator, control circuit and power transistor.

Last year I came across the handwritten report that I'd written for our team all those years ago. Our design used a mains-fed transformer, then low-voltage bridge rectifier, which may have been part of the "rules" that everyone had to abide by. So we were AC-only. We were given a huge Variac transformer to simulate the wide range of input mains voltages. We wound ours up to quite a bit beyond the 300 V maximum in our design requirements, to make sure that we could exceed the spec! The control circuit eventually switched the duty cycle off completely - it failed gracefully.

I remember us all being warned that the power transistor would not be able to handle full load current if it was on permanently, as opposed to being switched at 25 kHz. Before we finalised our design and made up a printed circuit board, we were developing our control circuit on a separate breadboard with a single-wire feed to the power transistor. That wire became accidentally disconnected during full-load testing. There was a noise like rustling leaves, a bit of magic smoke and then a rifle-shot crack. The transistor had exploded and fired itself into the ceiling of the lab 20 feet above us. After that, we were all made to wear safety specs... The mark in the ceiling was still there two years later in our final year!

Hmmm. I can believe that. What is odd is that everyone in the village, no matter which phase their house was on, got low voltage. You'd think that one house in three (between the two good phases) would have been OK. Certainly no-one in the village said on our Facebook group "it's fine for us". Weird.

I knew someone who made a portable battery pack to run their BBC micro. It was a 5' long section of drain pipe with a stack of 100 NiCd cells with a 13A socket araldited into one of the end caps. The beeb PSU was happy to run on 240V DC ... ok it would have stressed half the diodes, but it didn't seem to care.

Spot on. That is how it works. The availability if ultra low resistance very high speed switching MOSFETS jhas transformed the industry.

NY snipped-for-privacy@privacy.net wrote in news:10cp8g3$pvr$ snipped-for-privacy@dont-email.me:

That's not how it works, people are not fed with power between phases but between 'low' voltage[1] phase and neutral. On a low voltage supply that is

I have seen some examples where individual houses (in rural areas) are fed from the difference between phases. The main feed is 3 phase

That seems to be a standard arrangement, especially obvious where there is an outlying property which has two wires connected to two of the three 11 kV overhead lines and a single-phase transformer to feed 240 V (often by low voltage overhead lines) to the house/farm.

Our old house was the middle of a terrace of three. All four wires of

We had a really stupid arrangement in our server room at work. When it was refurbished, someone in Site Facilities decided to supply each of the several benches from a different mains phase. That meant that we were forbidden to connect (for example) a terminal on one bench to a server on another bench by RS-232 because of the risk of > 240 V (maybe

John R Walliker snipped-for-privacy@gmail.com wrote in news:10crikm$7tdq$ snipped-for-privacy@dont-email.me:

Of course, there is no neutral in the HV network so that is how it will be done in rural areas, it is routine.

Well if the three phase step down was in fact three *separate* transformers, only one phase would remain working at full power, whilst the other two were at effectively half power. Assuming a delta connection

But they are not three *separate* transforners. So it is more complex.

Brownie points for whoever can tell us what the voltage between the two

nib

Oops. Wrong. Not thinking. It's 11000V.

nib

There must be a geometric way to prove that, but I seem to have misplaced my Oxford Geometry Set.

Question:

What geometric construct, has as its output, a magnitude of SQRT(3) ?

CoPilot:

Several suggestions snipped...

That took me right back to my last job before retirement[1] - not a happy thing since retirement suits me much better.

OK, cheated and found a page full of math.

The hint I needed, was to make a phaser diagram.

Then the root of three popped out quite easily, from the geometry.

Only if the two phases have the same load, if not volts will sag on the higher loaded phase.

There's 22kv near me, and 20kv a little further north. Both Northern Electric (formerly NEEB) and old circuits.