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G8MNY > TECH 21.01.21 09:35z 103 Lines 5203 Bytes #999 (0) @ WW
BID : 20698_GB7CIP
Read: GUEST
Subj: Mains Power Protection.
Path: HB9ON<IW8PGT<IZ3LSV<IQ2LB<F1OYP<KE0GB<N7HPX<GB7CIP
Sent: 210121/0932Z @:GB7CIP.#32.GBR.EURO #:20698 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Aug 07)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
After a topic raised by Lodewijk PA3BNX, here is my proposed design for a
protector. Although spike suppresser 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 are abnormal loads
on the other phases you can get 300V mains quite easily! This certainly may
happen if a neighbour blows a 30A fuse, & 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 & I have
included a low frequency trip as well, as 220V @ 20Hz can burn up transformers!
Unlike mains spike protectors that attempt to snub voltages above 450V this
protector works like an ELCB/RCB (e.g. 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 ÄÄÄÄÄÄ)ÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄo\___ L LOAD
³ \Fuse
POOR ³ ÃÄ´>ÃÂÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄ¿ FAST
MAINS ³ ³ _³_ ³ ³ 47k 47k 100k 8W Lamp RELAY TRIP
< 219V ³ ³ /_\ ³ 47k ³ ³ ³ ³
or >253V³ ³ ³ ³+ 1u ³ 100k<¿ 47k 100k RELAY
N ÂÄÄÂÄÄÁÄ)ÄÄÄÄÙ ===400V ³ POT ³ ³ POT<¿ ³
³ 100k _³_ ³ ³ ³NEON2 ³ ³NEON3 ÃÄÄÄ¿
³ ³ /_\ ³ 47k ³ ³ ³ LED ³ ³ ³ ³
³ ³ ³ ³ 1u 16V ÃÄÄÄ)ÄÄ)ÄÄÄ)ÄÄ´>ÃÄÄ¿ ³ ³ ³a ³
_³_ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ g_³_ ³
/_\ ÃÄ´ÃÄ)ÄÄ´>ÃÄ)ÄÄÂÄÄÄ¿ ³/ ³ ³ ÃÄÂÄ´>ÃÄÁÄ)ÄÄÁÄÄ\_/ ³
³ ³ 1n ³ _³_ ³ +³ 100k<Ä´ ³ ³ ³/ +³ ³ SCR ³k o
³ NEON1 ³ /_\ ³ === POT ³\e 22k ÀÄ´ ===1u ³ ³ / RESET
³ ³ ³ ³ ³ ³ ³ T1 ³ ³ T2³\e ³16V 10k ³ ³ PUSH
ÀÄÄÁÄÄÄÄÁÄÄÁÄÄÄÄÁÄÄÁÄÄÄÁÄÄÄÄÄÁÄÄÄÁÄÄÄÄÄÄÁÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÙ
FREQ LOW V HIGH V
All Rs 0.5W 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 determined. 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, e.g. 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 TRIP
To trigger the SCR you just need a resistor chain with a pot across the 358V DC
with a small 80V neon lamp NEON3 (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 TRIP (if wanted)
For under voltage consider a voltage below 230 -10% = 292V peak where equipment
may not work properly & it is better to disconnect it (e.g. some PCs). The same
idea with pot & a NEON2 to an inverting low voltage NPN T2 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!
LOW FREQUENCY (if wanted)
NEON1 is light whenever there is mains present, its O-80V constant voltage
square wave is fed via 1nF to voltage doubler diodes to charge up the 1uF &
100k load pot with a voltage proportional to frequency. The pot takes a
fraction of this voltage to turn on NPN T1, when the frequency is 50Hz or
greater. If lower T1 collector via the steering LED diode & triggers the SCR.
RESET
A push switch lets you release the triggered SCR reset, as well as a lamp test.
This may needed on each power up of the circuit.
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Ú¿ MAINS IN (o)³ NEON1 Mains > 80V
³ ÀÙ RESET O ³ PUSH to reset output
³ TRIP (*) ³ LAMP indicates faulty power
³ >260 (o) ³ NEON3 mains > 380V peak
³ [] [] <200 (o) ³ NEON2 out if mains less < 300V peak
³ <50Hz o ³ LED
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
2 WIRE MAINS
Another power problem affecting hams is the use of 2 wire mains system, were
no separate 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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