OnLine Power Telecommunication - Manual (Page 22)

OnLine Power
1-7
REV A
1-6-6 Over Temperature Shutdown
While the PBC-II has several internal fans operating when the PBC-II & UPS Is ” ON ” to prevent an overheating
condition, further protection has been built into the UPS to ensure against circuit failure due to internal overheating.
If there is an Over Temperature condition, the UPS shall shut down. It has an auto-recovery feature, so that when
the temperature reaches a safe level, the UPS will come back on. There is a built-in hysteresis feature to prevent
any oscillatory condition of the UPS turning ” ON ” and ”OFF” at the Over Temperature trip point from taking place.
For overtemperature alarm condition and description, see Appendix A and E at the end.
1-6-7 Over Current Protection
If there is an overload or loads draw excessive output current from the PBC-II. The sensing circuit in the Inverter will
provide feedback to cause the Inverter to limit the current and thereby prevent the unit from being damaged due to
such a condition. For overload of over 160% of rated capacity, unit will shut down and/or trip breakers, same as in
output short circuit condition. For overload of 120% to 160% of rated capacity, “Summary Alarm” comes ON and the
unit may support the output load via automatic bypass circuit. See Appendix E at the end for details.
1-6-8 Auto Bypass Feature
This feature allows input power to bypass the electronics and UPS automatically. It detects the low or no output
voltage of the UPS and energizes the autobypass relay, whose contacts provides output power (from input or
battery, i.e. in AC or DC mode) to the main output breaker. The relay deenergizes or opens when output power falls
below the limit or disappears for any of the reason (such as overtemperature or any failure), thereby disconnecting
the UPS from output circuits. The normally close contacts of this relay provides input power to the output circuit with
this feature. As long as input power is available, it is provided to output circuits for continuous operation of
microcells, even though UPS may have been shut-off indicating “Summary Alarm” in the unit as well as in central
station via DB9 cable. See Appendix A and E for “Customer Action” under “Summary Alarm Conditions”.
1-6-9 System Operation
This PBC-II is supplying the power to critical load through bypass circuit directly by the input power source as long
as the input voltage range is within the voltage specification such as 85 V - 130 V for 120 Volt unit, 180 V - 264 V for
230 Volt unit. When the input voltages are out of the above specifications or fails, the unit will automatically transfer
to the battery and inverter to supply the critical load. When the input comes back to normal, then unit will supply
critical load automatically from the input source.
The transferring time from input power to battery or battery to input power is within 4.2 - 10 milliseconds at 100%
load condition.