| |
G8MNY > TECH 02.01.10 09:45l 123 Lines 5354 Bytes #999 (0) @ WW
BID : 46219_GB7CIP
Read: GUEST
Subj: Saveplug Motor Economiser
Path: IZ3LSV<IK2XDE<DB0RES<ON0AR<GB7CIP
Sent: 100101/2323Z @:GB7CIP.#32.GBR.EU #:46219 [Caterham] $:46219_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (New Jan 10)
(8 Bit ASCII Graphics use code page 437 or 850)
PRINCIPLE
These plugs can reduce the power used on fridge/freezer compressors & central
heating pumps motors. They reducing the mean supply voltage & an AC shaded pole
electric motor or a capacitor start AC motor, will normally run at reduced
voltage with very little reduction of mechanical output.
Output W full speed Input W
100% ´ .ú .---ÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Ã 400%
³ .ú' ' Þ95% 'OVER ³
75% ´ .ú' 'Ý .' HEAT Ã 200%
³' Þ' ú ³
50% ´ Ý 'ú . . . 'Saturated³ 100%
³ Stalled | Normal core ³
25% ´ / Ã 50%
³ __..-Ä' ³
0% ÅÄÄÄÄÂÄÄÄÄÂÄÄÄÄÂÄÄÄÄÂÄÄÄÄÂÄÄÄÄÂÄÁ 25%
140 160 180 200 220 240 260
Volts
In this graph the stalled motor power is about 4x the normal, some motors are
much more than this up to 15 times ! In a compressor situation the motor can
be easily stalled by powering off & on just after the pressure builds up, to
stop motor burn outs there is a built in thermal switch to turn off the power
for a few minutes while the gas pressure leaks away & the motor can start again
from no back pressure.
WAVEFORM
_ _
/~ ~\ |~ ~\
³ ³ ³ ³
³ ³ ³ __³ ³__ __
³ ³ ³ ³
³ ³ ³ ³
\_ _/ |_ _/
~ ~
On resistive loads the waveform looks something like this, but motors are not
resistive!
The power saving is not all it seems, as the slightly higher pulse currents can
also increase the copper losses & with the plug heat as well may negating any
saving.
CIRCUIT
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄE
³
³ ÚÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÂÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ³ 100k _³_ _³_ ³
³ ³ Diac ÃÄÄÄÄ¿ /_\ \_/ ³
³ ³ ___³___ ³ ÚÄÄ´ ÃÄÄ¿ ³
³ ÃÄ150Ä¿ /_\_\_/ ³ ³ _³_ _³_ ³ 15k
³ ³ ³ ³ ³ ³ \_/ /_\ ³ u22 ³ APPLIANCE
E ³ T2__³___ ÃÄÄÄÄ)ÄÄ)ÄÄÁÄÄÄÙ ÃÄÄ´ÃÄ¿ _³_
PLUG ³ /_\_\/ 180 ³ ³ u1 ³ ³ \_/ðOK
³ ³ \____³ === ÃÄ´ÃÄÄ390ÄÁÄ10MÄ´ ³LED
N L ³ ³ ³ u1³ ³ _³_ _³_
³ ³ ³ T1 ³ 100 ³ 22k \_/ \_/
³ ³ FILTER ³ ³<³/ ³ ³ ³ ³ ³
³ ³ ÃÄ´ ÃÄÄÄÄÄÂÄÄÁÄÄÄÄÁÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÁÄÄÄÄL
³ ÀÄÄÂÄÄ()))Ä´ ³>³ ===
³ u22 === ::: ÀÄÄÄÄÄ33RÄÙ u22
ÀÄÄÄÄÄÄÁÄÄ()))ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄN
OPERATION
Mains is fed through a filter in to power Triac T1 a BTA15, it is triggered by
the smaller Triac T2 a 2N6073. This in turn is triggered by the Diac. (this can
be just 2 identical low voltage transistors back to back). When the 0u1 cap
charged up through the 100k, reaches the Diac's breakdown voltage T2 triggers
& then T1, T1 triggering removes the power to T2 & hence T1 gate drive. T1
stays conducting until that half cycle AC current goes to zero (due to motor
inductance this will be later than the AC voltage).
The bridge rectifier & load across the Diac is some stabilising circuit for
peak loads.
Note that the fraction of mains removed is always about the same & not voltage
regulated (pity). On 250V in you get about 230V RMS out.
POWER SAVED
To determine this any power measurement needs a good true RMS power meter, it
is no good using an mean or RMS amp & volt meter! For complex wave shapes phase
angles between I & V, instant multiplication of these must be done. With modern
uProc meters this is now possible to good accuracy!
ÚÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄÄÄ¿
Mains Ä´True ÃÄÄÄÄÄÄÄÄÄ´Appliance ³ Get the full range of
³Power³ ³under test³ Powers used, including
³Meter³ ÀÄÄÄÄÄÄÄÄÄÄÙ stalled/start motor power.
ÀÄÄÄÄÄÙ
ÚÄÄÄÄÄ¿ ÚÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄÄÄ¿
Mains Ä´True ÃÄ´SaverÃÄ´Appliance ³ Get the full range of
³Power³ ³plug ³ ³under test³ Powers used, including
³Meter³ ÀÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÙ stalled/start motor power.
ÀÄÄÄÄÄÙ Check the motor always starts!!
Power savings will very much depend on the normal mains supply voltage & the
amount of over saturation that occurs in that make of motor at that voltage,
Typical savings on say a 100W 220V motor on max EU 253V might be 50W with 8W
warming the plug. The same motor on 230V might be 10W with 6W lost in the plug!
A less saturated 230V motor on 253V might not see any saving! You do need to
measure it to know if it is worth while fitting the plug.
RADIO NOISE
The plug is well filtered to the mains side, but none to the motor, so the
wiring to that needs to be short is LF QRM is to be kept low.
See my tech buls on "UK 13A Fused Mains Plug", "Maplin Mains Meter 2000MU-UK"
"AC Theory","Transistors, SCRs & TRIACs","Variacs", "Economy Turn ON Timer"
& "Meter Movement Types".
Why don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
Read previous mail | Read next mail
| |
