23
Theory of Operation
Section 7
7.1
Systems Description:
7.1.1 General Overview:
Dimensions Battery Backup Systems (BBS) consists of
four main components: The BBS module with a built-in battery charger, the manual
bypass switch (MBPS), 30A transfer relay (30ATR) or the Combined Manual Bypass
Switch (MBPS-30ATR), and two or four 12VDC AGM sealed batteries along with the DC
and AC cable connectors.
7.1.2 BBS Module:
The BBS module has two basic modes of operation described
below: Inverter mode and Standby mode. The Inverter mode operation can be either
“full power” backup or “red flash” operation (see dry-relay wiring configuration below).
1)
Inverter Mode: The direct current (DC) that enters the inverter from the batteries
is filtered by a large input capacitor and switched “On” and “Off” by the Metal Oxide
Silicon Field Effect Transistors (MOSFET) at a rate of 60 cycles per second, and fed
into the transformer which steps the voltage up to 120 volts. The inverter has a 16
MHz microprocessor to control the output voltage and frequency as the DC input
voltage and/or output load varies. The 120VAC, 60Hz voltage signal output
waveform generated by the inverter is called pure sine.
1.1)
Full Power Backup: The BBS was designed to supply full backup power
within the BBS rating. No dry-relay wiring connection is needed.
1.2) Red Flash Mode Operation: The BBS can operate in “Red Flash Mode” by
wiring the appropriate dry relay contacts to the traffic light controller red
flash switch circuit. There are three (3) double-pole double-throw (DPDT) dry
relay contact closures (NO: Normally Open, C: Common and NC: Normally
Closed) available on two terminal blocks (one side of each relay on each
block) with #6/32 screw terminals rated at a minimum 120V/1A, and labeled
so as to identify each contact, see Figure 9, page 16. The terminal block
wiring is protected with a clear plastic cover. There is a corresponding LED
indication when each relay is activated, see Figure 1, items (10), (11) & (12)
on page 5. All relays are deactivated when the inverter switch is off.
The Dry relay contacts energizes as follows:
a)
The
“On Batt.”
Relay Contact A (NO, C, NC): These relay contact
closures are energized whenever the unit switches to Inverter mode
(Battery Backup).
b)
The
“Low Batt.”
Relay Contact B (NO, C, NC): These relay contact
closures are energized whenever the battery approaches the useful
battery capacity remaining reference point (40% in most applications)
chosen by the user. See settings on section 5.1, page 17.
c)
The
“Timer”
Relay Contact C (NO, C, NC): These contact closures
are energized two hours after the unit switches to Inverter mode (Battery
Backup).
