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S&C Instruction Sheet 653-506
System Operation
Under normal conditions, power is supplied from the utility grid to the critical load through
the input circuit breaker, power electronic switch (PES), and output isolation circuit breaker.
The system’s utility disturbance monitor (UDM) continuously monitors the supply voltage
for a disturbance activity. When a disturbance occurs, the PureWave UPS System turns on the
system’s high-power inverter(s). The stored energy in the system’s batteries is converted to ac
and supplied through a voltage-matching isolation transformer while the PES is commanded
off (open) to isolate the customer’s critical loads from the faulted utility. Output power matches
the customer load for one minute at full load (or up to three minutes at reduced power) during
the utility voltage disturbance or momentary power interruption.
The entire transfer sequence occurs typically within 1 to 4 milliseconds (less than ¼ cycle).
An electrically operated bypass circuit breaker permits continued service to the customer
from the utility in the event the PureWave UPS System is out of service for maintenance. See
Figure 10 for a diagram of the PureWave UPS System.
Figure 10. Diagram of the PureWave UPS System.
Operating States
Listed in Table 1 are the operating states of the PureWave UPS System. Depending on the
alarm condition encountered, the system can be in any of these states. The user interface
shall inform the user of the system’s present state. Table 1 lists and describes each state.
Table 1. Operating States for the PureWave UPS System.
States
Description
Ready
In this state, the PureWave UPS System is ready to
protect the load in the event of a disturbance .
Run
In this state, the PureWave UPS System is running to
protect the load from a utility disturbance . The inverters
are on, and the PES is open .
Inhibit
In this state, the PureWave UPS System has been
inhibited from running; however, the load is being fed
through the PES . The bypass circuit remains open .
Bypass
In this state, the bypass circuit breaker has been closed;
however, the input and output circuit breakers remain
closed .
Bypass Isolate
In this state, the bypass circuit breaker is closed, and
the input and output circuit breakers are open .
Test in Bypass
This state is used during the startup of the PureWave
UPS System or during service . This state permits the
system to perform runs while the load is being fed
from the utility through the bypass circuit breaker . In
this state, the bypass circuit breaker is closed, and the
output circuit breaker is open .
Operation