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G8MNY > TECH 21.06.22 08:30l 174 Lines 7818 Bytes #999 (0) @ WW
BID : 24211_GB7CIP
Read: GUEST
Subj: Constant Voltage Transformers
Path: IW8PGT<LU4ECL<GB7CIP
Sent: 220621/0628Z @:GB7CIP.#32.GBR.EURO #:24211 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Oct 07)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Here is information about the principle of tuned saturated transformer type, of
constant voltage mains transformer for power conditioning. This is not the same
as the modern uninterruptable battery SM mode (RF generators) fast inverters
that fill in holes in the mains, but a far simpler highly reliable passive
system.
MAGNETIC SATURATION
Flux _____
IRON ³ _.-~~/'~ The BH curve shows the magnetic
LAMINATE ³./' ./' flux B saturate & flattens off as
./³ ./ the magnetising effort in Amp Turns
ÄÄÄÄÄÄÄÄÄ/ÄÄÅÄÄ/ÄÄÄÄÄÄÄÄÄ +H increases. This is the heart of the
./' ³/' Amp Turns regulation principle.
./' _./'³
_.:..-" ³-B
~~~~
The transformer secondary it tuned with a capacitor, & it literally sucks all
the power it can from the nearby primary magnetic circuit until the tuned core
is saturated.
2 MAGNETIC CIRCUITS
Unlike a conventional transformer the primary & secondary are on different
bobbins (coil formers) & are not tightly magnetically coupled. There is a
magnetic filler piece put in between 2 bobbins typically with an air gap.
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
Simple CVT ³ ÚÄÄÄ¿ ÚÄÄÄ¿ ³
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ ³T~~~~~~~~~T³ ³
³ ÚÄÄÄ¿ ÚÄÄÄ¿ ³ ³ ³|BUCK COIL|³ ³
³ ³T~~~~~~~~~T³ ³ ³ ³ÏÍÍÑÍÍÍÑÍÍϳ ³
³ ³| TUNED & |³ ³ ³ ³ \_/ Gap³ ³ More Complex
³ ³| LOAD |³ ³ Specially ³ ³ ³\_/³ ³ ³ "ADVANCE"
³ ³| BOBBIN |³ ³ shaped ³ ³T~~~~~~~~~T³ ³ CVT
³ ³ÏÍÍÑÍÍÍÑÍÍϳ ³ transformer ³ ³| TUNED & |³ ³
³Gap~~³³ ³³~~Gap³ laminates. ³ ³| LOAD |³ ³
³ ÚÄÄÙ³ ³ÀÄÄ¿ ³ ³ ³ÏÍÍÑÍÍÍÑÍÍϳ ³
³ ³T~~~~~~~~~T³ ³ ³Gap~~³³ ³³~~Gap³
³ ³| MAINS |³ ³ ³ ÚÄÄÙ³ ³ÀÄÄ¿ ³
³ ³| BOBBIN |³ ³ ³ ³T~~~~~~~~~T³ ³
³ ³ÏÍÍÑÍÍÍÑÍÍϳ ³ ³ ³| MAINS |³ ³
³ ~~~ ~~~ ³ ³ ³ÏÍÍÑÍÍÍÑÍÍϳ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ³ ~~~ ~~~ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
ELECTRICAL CIRCUITS
For employment inside equipment __
the secondary load windings are ==||( ³ 50Hz
wound with the tuned circuit ÄÄÄÄÄÄ¿ || ||( === tuned
winding. 50Hz )|| ||(__³ winding
The power flowing in the tuned Supply )|| || _____
winding must equal the maximum )|| ||( Regulated
load for the system to regulate. ÄÄÄÄÄÄÙ || ||(_____ Secondary
With fairly fixed loads this || || _____ Windings
simple circuit will do. ==||(_____ Outputs
Specialist regulation transformers with greater regulation demands & changing
loads use bucking arrangements to improve the regulation.
ADVANCE 1004 CVT
______ ÚÄÄÄÄÄÄÄ¿ 50Hz Tuned
|Ú-ÂÂ-¿|( 620V ³ 1kW of power!
|| || ||( Buck ³
L>ÄÄÄÄÄ¿ || || ||(_Coil === 24uF
50Hz )|| |Æ µ| _³ ³ 660V AC
180- )||gaps||( 600V ³
270V )|| || ||( ³
N>ÄÄÄÄÄÙ || || ||(_ÚÄÄÄÄÄÄ)ÄÄÄÄÄÄ>L
|| || ||( 245V ³ Fully Isolated &
|À-ÁÁ-Ù|( ³ Regulated power
³~~~~~~ ÀÄÄÄÄÄÄÄÁÄÄÄÄÄÄ>N
³
E>ÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ>E
REGULATION
Output ADVANCE Type 1004
Volts
/³\ /
250´ /
³ No Load /_ _ . - - O/P 244V ñ2.5V for ñ40V I/P
245´ _ . - Ä ' ~ /_ _ . . -
³ _ . - ~ _ . - Ä ~ / O/P 240V ñ3V for ñ40V I/P
240´- ~ _ . - ~ /
³. - ~ @ 500W Load / _ . - Ä
235´ ./- ' ~ O/P 230V ñ5V for ñ40V I/P
³ _.- ~ /
230´ _. -~ /WITH
³ .-~ /NO CVT
225´ .ú'@ 1kW Load /
³ / /
220ÅÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄ>Input
180 190 200 210 220 230 240 250 260 270 Volts
The regulation only occurs of course at the resonant frequency. The output is a
fairly low distortion sine wave but not that good. Note that the output rapidly
drops with the heavy overload, & in fact overloads tend to give a fairly safe
constant current at just over the maximum current rating.
IN USE
Although they are very useful for ensuring the correct voltage, more & more
equipment is immune to small power line fluctuations, except extreme voltages,
so the need for a CVT is less apparent today.
They are not so useful for computer kit as you might think, as the power off
through one, causes the supply to fail over a few cycles, exactly the brown out
synareo that can damage data on computers! Also the very high power TURN ON
surge of a CRT screen power (e.g. 100W screen running but a 4kW surge) ensures
a glitch will be caused on a low power CVT if the CRT is on the same CVT as the
processor.
They are also not much use on a generator supply, unless the frequency is
fairly close to 50Hz for it to function properly.
Power efficiency is also not good at about 10% of the full load is lost all the
time as heat.
I have used the 1kW one for /P OK, on a VERY long multiple spurred mains feed
(1km) where the mains was liable to be all over the place. The isolation was
an added safety feature, as too was the RF mains isolation.
Site 1km tapped long cable 180-240V?
Mains ÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄCVTÄ> Ham /P shack
230V? Other unknown intermittant loads Isolated 240V
It worked OK that is, until someone turned on a small kettle (Diode load type!)
that DC saturated the core!
AS A SINE WAVE INVERTER
Using the same magnetic arrangement, but starting with a square wave low
voltage inverted input instead of the mains primary, then a simple inverter can
give a regulated sine wave output, but the efficiency is low (70%).
O/P 1ÄÄ¿ === ____ 50Hz
)|| ||( ³Tuned
+11-13V____)|| ||(_ÚÄÄ)ÄÄÄÄÄÄÄ230V
Square )|| ||( === ñ10V
50Hz Wave )|| ||(____³_______Sine Wave
O/P 2ÄÄÙ ===
WITH MOTOR DRIVEN VARIAC
For really good regulation the mains can be preconditioned with a motorised
variac.
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
MOTOR - - - - - - - - - - - - MOTOR ³ÚÄÄÄÄÄÄÄÄÄÄÄÄ¿³
/ ³ ³ ³³ ³~~³ ³~~~³ ³³
/ )|| === ____ CONTROL ³³ ³ ³ ³CVT³ ³³
LÄÄÄÄ>)||______ || ||( ³ ³ ³ ³³ ³--³ ³---³ ³³
160- .)|| 210- )|| ||(_ÚÄÄ)ÄÄÄÁÄÄ)ÄÄÄÄ ³ÀÄÄÄÄÄÄÄÄÄÄÄÄÙ³
290V stop)|| 250V )|| ||( === ³ 230V ñ2V ³ .--~~~--.(M)³
)|| )|| ||(____³______³____ 0 - 6kW ³ / Varicac \ ³
NÄÄÄÄÁÄÄÄÄÄÄÄÄÙ === ³|o--( o ) | ³
VARIAC CVT ³ \ / ³
³ '--__--' ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
A decision circuit drives the motor to set the output exactly at 230V after a
second or so. The CVT has to try to take care of spikes & dips that the variac
motor control loop can't follow.
This arrangement takes care of changing losses due to varying loads too, & used
to be the Bees & Eees for fussy valve gear on unknown mains.
See my buls on "Variacs", "Maplin Mains Meter 2000MU-UK", "Portable Appliance
Testing" & also "Mains Power Protection".
Why don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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