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G8MNY > TECH 25.04.24 03:03z 138 Lines 6380 Bytes #29 (0) @ WW
BID : 5849_GB7CIP
Subj: Small Tripp-lite 300W UPS
Path: SR8BBS<SR4BBX<SR1BSZ<EA2RCF<I0OJJ<GB7CIP
Sent: 240420/0955Z @:GB7CIP.#32.GBR.EURO #:5849 [Caterham Surrey GBR] $:5849_GB
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (New Jul 17)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
This is a small 1U rack mounted SmartPro UPS. Its backup power is from a 50Hz
pulse width stepped square wave mains inverter all from 2 small 7AH 6V
batteries when in backup mode (e.g. 35A @ 11V ?) It features step up voltage
conditioning & over voltage shutdown to invert mode.
FRONT REAR
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ øøøøø ³ ³±±±±± __ _ 0 o [][][][][][][][]³
³ () () ³ ³±±±±± ~~ ~ ß [][][][][][][][]³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Card 232 USB trip gnd ----UPS--- OutIn
/~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ .-~~~~-. | ³
³ / \ | ³
³ ³ MAINS ³ | 2x 6V 7AH ³
³ ³ TRANS- ³ | BATTERIES ³
³ ³ FORMER ³ | ³
³ ³ ³ | ³
³------. \ / | ³
³ DATA | '-____-' |____________________________³
³ UNIT |ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿³
³ |³ VMOS REG 5 4 3 2 ³³ Relay1 Mains In
³ |³remote VMOS 1³³ 2 In Volts
³ |³control ___________________________³³ 3 O/P
³ |³_____________________³ 6 IEC UPS OUTPUTS OUT IN³ 4 Sw O/P1
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ 5 Sw O/P2 opt
232 USB epo Trip gnd
DESCRIPTION
The transformer has tapped primary & 3 secondaries, one centre tapped on the
+12V to the inverter VMOS. Another one for the control supply & the 3rd for
remote control features. IEC outputs 1 remotely switched eg. hard reboot (2nd
optional on PCB), & 1 non UPS O/P for surge loads (eg. CRT display).
INVERTER OUTPUT WAVEFORM with load (ringy from transformer & filter)
+340V´ ÚÄÄÄ¿ Peak Voltage depends on Battery state & Load current!
+230V³ ³ ³ Pulse width varies to get 230V RMS?
³ ³ ³
0V ´ÄÄÙ ÀÄÄÄ¿ ÚÄ
³ ³ ³
-230V³ ³ ³
-340V´ ÀÄÄÄÙ
USES
Mainly for computerised kit, that might suffer file corruption, or even HDD
damage on some power fails. But note a "non on line" UPS can still be fooled by
bad "brown outs", where the mains voltage does not go straight out, but has a
few cycles close to the kit's PSU safe minimum voltage (e.g. drops to 150V for
1 second while someone is blowing a fuse & then out!) So kit PSU becomes
desperate for power & the UPS does not "cut in" in time to stop the kit's PSU
giving illegal & corrupting voltages especially to CPUs, memories, & HDDs.
UNMANNED SITE MODIFICATIONS
As with most UPSs, this UPS is not suitable for an unmanned site, because when
the battery is emptied/fails on a long discharge. Not only does the output fail
but the UPS can then stays in OFF mode with no output power, even when the
mains is restored!
Initially I designed 3 modifications to help solve this...
1/ EXTERNAL BATTERY
As this UPS has an isolated 12V battery system, it is possable add in an
external fused (30A) battery. This reduces the occurence of a flat battery &
extends the backup time.
I removed the back plate & PCB, added a heavy -ve lead soldered to the PCB
battery connection. The +ve lead is spliced to the transformer centre tap. Both
exit the rear panel through drilled holes & rubber gromets, to a chock block
next to the earth screw. For safety the -ve can be earthed to that terminal.
2/ AUTO ON RE-START
I wanted the UPS to come back in automatically when the mains is restored after
an exhausted battery.
+5V ÄÂÄÄÄ¿ ÚÄÄÄÂÄÄÄÄÄÄÄ>ON LOGIC
R 10K 100u ³/ ³ ON
³ ÀÄÄÄ´ÃÄÂÄÄ´ /button
LEDs + 10K ³\e ³
ÄÄÄÁÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÁÄÄÄÁÄÄÄÄÄÄÄÄ0V
On scoping around the front panel LED PCB, the ON button has +12V on standby &
+5V on run. A NPN transistor & a power up low CR will short the ON button for
long enough when external power come back if there is battery voltage left.
NB the invert mode normally stops (RED LED) before the battery is totally flat.
3/ MAINS POWER WHEN OFF.
I wanted the load to see mains power if the UPS is turned off. Four relays
control the mains switching of the auto-transformer is something like this..
8A MAINS OK Hi______\____________>UPS IEC
MAINS >ÄÄTripÄÄÂÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄ\_______/___)|| ³ ³ OUTPUTs
IN IEC ³ Isolated IN Low )|| OUT \ \__>Switched
Surge detector )|| ³_____>Sw option
IEC OUT circuit N_______)||______________>
||
||((secondaries)
The transistor operating the OUT relay needed to be turn on when external mains
is present. The nearby detector IC U1 pin 14 provided +5V on mains OK, & a 1K
to U601 base is all that was needed.
+12VÄÄÄ¿
ÚÄÄÁÄÄ¿
³ OUT ³
ÀÄÄÂÄÄÙ 14³
ÚÄÄ´ U601 ÚÄÄÄ1KÄÄÄÄ´IC U1
_³_ \³ ³ ³Mains
/_\ ÃÄÄÄÄ´ ³Detector
³ e/³ ÀÄR601-<On
ÄÁÄÄÁÄÄ Logic
But on 2nd thoughts. I removed relays 3 & 4, & strapped the contacts instead.
This saved 2x 12V relay currents & improved reliability etc.
REMOTE
As the remote feature was not wanted, & just power it down unfortunately
"switched off" the UPS. So I investigated & found a short (solder blob) on the
2nd opto isolator under the "power trip" stopped this, & the isolated
transformer power for the remote could then be left out OK.
CONCLUSION
These 3 mods results in a UPS that comes back on automatically, even when the
battery is exhausted (not flat). And when the UPS function is "switched off" it
still gives voltage step up output if needed from good valid mains.
Why don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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