Symmetra Power Array Input Voltage Selector Theory of Operation

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Issue:
This document describes how the input voltage selector block of the Symmetra Power Array (NAM) works.

Product Line:
Symmetra Power Array

Environment:
NAM models only

Cause:
This document describes how the input voltage selector block of the Symmetra Power Array (NAM) works. This is useful for understanding the theory of operation or for troubleshooting.

Resolution:
The input voltage selector switch is primarily responsible for two things: routing power through the appropriate taps of the isolation transformer and notifying the intelligence modules of the expected input voltage.

The reason that the IMs need to know the expected input voltage is so that the automatic bypass functionality can operate properly. If the input differs drastically from the jumper setting, a bypass out of range message will be displayed and the UPS will not be capable of transferring to command or temporary bypass.

When the jumper is set to the up position, it makes contact with the microswitch at the top of the block. This will notify the IMs to expect 240 VAC and will also jump the bypass source to the 240 VAC tap.

When the jumper is not set (down position), the microswitch is open and the IM assumes 208 VAC input. This also jumps the bypass to source to the 208 VAC tap.

When on inverter, the power modules will output 240 VAC all the time and therefore the inverter output only needs to connect to the 240 VAC tap of the transformer. The setting of the jumper is only necessary to obtain correct voltages while in bypass. If the jumper is not set correctly, the user will only realize it when in temporary, command, or manual bypass.