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home | newest check | boards | help index | log | ps | userlogin | send sysop | slog | status forward | bcm news | users | version | remove cookieG8MNY > TECH 20.04.24 19:01l 138 Lines 6380 Bytes #1 (0) @ WW BID : 5849_GB7CIP Read: GUEST Subj: Small Tripp-lite 300W UPS Path: JH4XSY<IW0QNL<HB9ON<IW8PGT<LU4ECL<ED1ZAC<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 Ŀ Ŀ __ _ 0 o [][][][][][][][] () () ~~ ~ [][][][][][][][] Card 232 USB trip gnd ----UPS--- OutIn /~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\ Ŀ .-~~~~-. | / \ | MAINS | 2x 6V 7AH TRANS- | BATTERIES FORMER | | ------. \ / | DATA | '-____-' |____________________________ UNIT |Ŀ | VMOS REG 5 4 3 2 Relay1 Mains In |remote VMOS 1 2 In Volts |control ___________________________ 3 O/P |_____________________ 6 IEC UPS OUTPUTS OUT IN 4 Sw O/P1 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 Ŀ Peak Voltage depends on Battery state & Load current! +230V Pulse width varies to get 230V RMS? 0V Ŀ -230V -340V 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 Ŀ >ON LOGIC R 10K 100u / ON ĴĴ /button LEDs + 10K \e 0V 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 >Trip\_______/___)|| OUTPUTs IN IEC Isolated IN Low )|| OUT \ \__>Switched Surge detector )|| _____>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. +12VĿ Ŀ OUT 14 Ĵ U601 1KĴIC U1 __ \ Mains /_\ Ĵ Detector e/ R601-<On 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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