Liebert NX UPS System user manual Static Transfer Switch, Battery Temperature Compensation

Operation

5.1.2Static Transfer Switch

The circuit blocks labeled Static Switch in Figure 27 contain electronically controlled switching cir- cuits that enable the critical load to be connected to either the inverter output or to a bypass power source via the static bypass line. During normal system operation the load is connected to the inverter; but in the event of a UPS overload or inverter failure, the load is automatically transferred to the static bypass line.

To provide a clean (no-break) load transfer between the inverter output and static bypass line, the static switch activates, connecting the load to bypass. To achieve this, the inverter output and bypass supply must be fully synchronized during normal operating conditions. This is achieved through the inverter control electronics, which make the inverter frequency track that of the static bypass supply, provided that the bypass remains within an acceptable frequency window.

A manually controlled, maintenance bypass supply is incorporated into the UPS design. It enables the critical load to be powered from the utility (bypass) supply while the UPS is shut down for routine maintenance.

NOTE

When the UPS is operating in bypass mode or on maintenance bypass, the connected equipment is not protected from power failures or surges and sags.

5.1.3Battery Temperature Compensation

For 10-30kVA UPS with internal batteries, a standard temperature probe is installed to measure the internal battery temperature to optimize battery management. The measured temperature can be displayed from the UPS front panel.

For UPS with external batteries, an optional battery temperature interface equally optimises the external battery management by connecting up to four external temperature sensors from the battery cabinet(s) to a control unit inside the UPS.

Figure 28 Multiple battery temperature sensors

	Temperature
	Sensor
+	NC
	12V
IN
-	OUT
	GND
	TMP-2
	Temperature
	Sensor
+	NC
	12V
IN
	OUT
-
	GND
	TMP-2
	Temperature
	Sensor
+	NC
	12V
IN
	OUT
-
	GND
	TMP-2
	Temperature
	Sensor
+	NC
	12V
IN	OUT
-
	GND
	TMP-2

X103

X104

X108

+12V OUT GND

X105

BCB Control

Board – C2

X106

BCB Box

	Monitor
X7	Board
	– U2

-12V BAT-T GND

UPS

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