OnLine Power
(6002-1646) REV.X8 20
3-2-2 Tur ni ng off the Fire Alar m Back- up UPS 1481 :
1. Turn off the Output Breaker(s), if prov id ed.
2. Turn off the Battery Breaker.
3. Turn off t he I n put Breaker, if provided.
3-3 Theory of Operation
Illustration NO TAG is a simplifi ed block diagram of the Fire Alar m Bac k - up UPS1481. This
diagram provides an excell ent t ool i n identifying the major buildin g blocks within the Fire
Alarm Back-up UPS1481 .
1. External Main input circuit breaker (CB2) — The main input circuit power provides
overcurrent protection to the i nput side of the Fire Alarm Back -u p UPS1481 .
2. Input Contactor (KI) — The microprocessor based control circuit ry :
• Verifies UPS to be normal condit io n and not the one ‘at fault”.
• Verifies correct input volt a ge and frequency to be within acc eptable range and
commands the closure of this. C ont actor via control transforme r T 2 a nd fuse Fl.
3. Input Chokes (LI, U) — They act as a filter and an important circ uitry of an up chopper,
boosting input voltage to a high er i nternal DC bus voltage.
4. Battery charger — T he b attery charger converts A C po w er i nto regulated DC power to
charge and to maintain the cha rge on the battery bank. The cha rg er is fully automatic with
a current limiting feature so that d amage will not occur to the batteri es in case of a charger
malfunction. The charger is s iz ed s uch that the batteries will be maint ained at full charge
even when the input voltage is at t he lo w line limit for indefinite periods of t im e.
5. Battery — The battery bank, consisting of eig ht (8), ten (10), sixteen (16), or tw ent y (2 0),
12 volt, VRLA batteries, prov ides t h e reserve energy to power the l oa d when suitable AC
input power is not present. The b atteries are sealed, maintena nc e—free construction.
6. Inverter — When the AC input power is not av ailable to power the load, the inve rter
converts the energy stored in t he battery bank to AC power to supply t h e powers the load.
The pulse width modulated (P WM) inverter utilizes high spee d, hi gh efficiency IGBT5 for
fast response, sinusoidal po w er.
7. DC Choke (U) — If helps boosting battery voltag e to an internal higher DC bus voltag e.
8. Output AC Choke (L4) — This acts as a buck circuit component connect i ng high DC bus
voltage to an appropriate AC out p ut voltage.