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G8MNY > TECH 26.05.07 19:01l 78 Lines 4026 Bytes #999 (0) @ WW
BID : 16132_GB7CIP
Read: GUEST OE7FMI
Subj: Mains Power Protection.
Path: DB0FHN<DB0FOR<DB0SIF<DB0MRW<DK0WUE<DB0RES<F5GOV<F4BWT<I0TVL<LA1SFS<
GB7CIP
Sent: 070526/1743Z @:GB7CIP.#32.GBR.EU #:16132 [Caterham] $:16132_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Updated Feb 07)
(8 Bit ASCII Graphics use code page 437 or 850)
After a topic raised by Lodewijk PA3BNX, here is my proposed design for a
protector. Although spike suppressor plugs etc act fast & do protect to a
certain point by blowing fuses, they don't act until the voltage is over 400V.
The problems about high mains are often due to the neutral having high
resistance at the substation, so if the 3 phase street loads are balanced,
there is little current so nothing gets hot. But when there is abnormal loads
on the other phases you can get 300V mains quite easily! This certainly may
happen if a neighbour blows a 30A fuse, and you get a large pulse on the other
2 phases. This may be enough to blow up a SMPSU etc.
Such a protector is also jolly useful on dodgy generator supplies!
Unlike mains spike protectors that attempt to snub voltages above 450v this
protector works like an ELCB/RCB (eg. an old one could be used as a starting
point) & shuts power off to the load, if the voltage is too high or too low.
___________________________________________________________ N
³ PROTECTED
L ÄÄÄÄÄÄÄ)ÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄo\___ L LOAD
³ ³
POOR ³ Ào-oÄÂÄ´>ÃÄÂÄÄÂÄÄÄÂÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄ¿ FAST
MAINS ³ Fuse_³_ _³_ ³ 47k 47k 100k 8W Lamp RELAY TRIP
< 219V ³ /_\ /_\ ³ ³ ³ ³ ³
or >253V ³ ³ ³ ³ 100k 47k 100k RELAY
N ÄÄÄÄÄÄÄÁÄÄÂÄÄÄ)ÄÄÄÄÄÙ ³ POT<Ä¿ ³ POT<ÄÄÄ¿ ÃÄÄÄ¿
³ ³ ³ ³ NEON1³ ³ NEON2 a³ ³
All Rs _³_ ³ ³ ³ ³ ³ 1uF ³ ³ g_³_ ³
0.5W /_\ ³ 1uF === ³ ³ ÃÄÄÄÄÂÄÄ)Ä´>ÃÄÁÄÄÄÄ\_/ o ,
³ ³ 400V ³ 22k ³_³/ === ³ SCR ³k / RESET
³ ³ ³ ³ ³\e 10V³ 10k ³ ³ PUSH
ÀÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÁÄÄÄÄÄÄÄÁÄÄÄÄÁÄÄÁÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÙ
SET LOW SET HIGH
TRIP TRIP
For 230V ñ10% the RMS max is 253V which is 358V peak. So using a bridge
rectifier & small capacitor, the peak voltage is determind. This can be on the
mains direct with dangerous voltages as here, or using a transformer which is
rated for 260V (before saturation!) to a lower voltage circuit.
The release relay here is a ZAP system, eg. a sensitive SCR puts 350V DC into a
110V relay via a Resistor (small) lamp from the 358V DC. This gives very fast
mains break times & the lamp reduces the hold current to a nominal level
suitable for the relay.
OVER VOLTAGE
To trigger the SCR you just need a resistor chain with a pot across the 358V DC
with a small 80V neon lamp NEON2 (or zener) from slider to the gate. The neon
will tell you if the mains is still over voltage & the Lamp that the relay is
operated disconnecting the load.
UNDER VOLTAGE
For under voltage consider a voltage below 230 -10% = 292V peak where equipment
may not work properly & it is better to disconnect it (eg. some PCs). The same
idea with pot & a NEON1 to an inverting low voltage NPN transistor then via a
diode to the same SCR gate as before. The trouble with this is that very low
voltages will let the relay release & apply low mains to the kit. If this is a
concern then a release relay system could be used but these are slower!
A push switch lets you relase the triggered SCR reset, as well as a lamp test.
2 WIRE MAINS
Another power problem affecting hams is the use of 2 wire mains system, were
no earth is used, they call the neutral the earth!! This is OK with plastic
water & gas pipes, but very dangerous if you have a real earth. Houses have
been burnt down due to that, as the 30/60A earth wire used for bonding to
earths, can't take the whole 200A street neutral imbalance current!
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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