As illustrated on the Power System
One-Line on Page 1.1-8, a medium-voltage Clean Power VFD is available
for use with 4.16 kV motors. The input voltage can be either 4.16 kV or its internal
phase shifting transformer can be configured to step-down a higher input
voltage, such as 13.8 kV, to power a 4.16 kV motor.
Medium-voltage VFDs are
used to start and control the speed of high horsepower motors in sewage and
fresh water pumping applications. They are also used on medium-voltage high hp
HVAC chillers. See Tab 10 for details.
Below the MCC in Figure 1.1-13 is
IFS-DF7A. This is an assembly that allows several pieces of electrical distribution
equipment to be pre-wired into a switchboard at Eaton’s manufacturing facility.
As shown, the IFS includes a 480/277 V main breaker feeding a 480/277 Vac 225 A
lighting control panelboard.
A 75 kVA 480 V to 208/120 V transformer is also part
of the IFS switchboard. It feeds a 208/120 V panelboard with remote control breakers
to feed various receptacle loads.
The Integrated Facility System Switchboard
(IFS) arrangement, as shown in Figure 1.1-15 is a great alternative to
traditional wall-mounted panelboards and floor or trapeze mounted transformers.
Because all of this equipment comes as a prewired assembly, it generally takes
less floor and wall space than traditional construction methods. It also
reduces installation time and labor costs.
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Figure 1.1-15. Integrated Facility System Switchboards
Figure 1.1-16 shows one possible application of an Eaton 9395 uninterruptable power supply (UPS-1) being fed through automatic transfer switch (ATS-A). This arrangement addresses a potential loss of power from switchgear SUS-F1A.
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Figure 1.1-16. UPS-1 Connection Option 1
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During normal operation, power flows from the
“Preferred” Normal source from breaker DF12A in switchgear SUS-F1A, through the
ATS feeding the inputs to the rectifier input breaker (RIB) and manual isolation
switch (MIS).
When power is lost at the input to ATS-A, the ATS sends a run
command to Generator A. While the generator isstarting and no power is
available to the UPS, the UPS inverter will use the DC energy stored in its
batteries to generate an AC sine wave to feed the loads.
As soon as generator
power is available, the ATS will transfer to the generator source and begin to
feed the UPS’s inverter section.
In this arrangement, consideration would need
to be given to generator stability. An ATS or generator failure would potentially
result in the UPS running on batteries until they were out of reserve power.
If
this approaches is utilized, the ATS should be of the BYPASS/ISOLATION design
as indicated on the One-Line. Eaton’s contactor-based BYPASS/ ISOLATION
transfer switch is available with removable contactors. This permits them to be
interchanged with a spare or the alternate source contactor during maintenance
and testing.
A second option for feeding the UPS would be to avoid providing
the ATS and feed the “MBP” and “BIB” from one breaker in switchgear SUS-F1A and
the “RIB” input breaker from one breaker in switchgear SUS-F1A and the “BIB” input
breaker from another as shown in Figure 1.1-17.
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| Figure 1.1-17. UPS-1 Connection Option 2 |
This would provide an alternate path to
supply the UPS during a maintenance event, such as servicing a breaker or cable
termination. Unfortunately, in the event of a power outage to the “SUS-F1A”
switchgear, due to substation transformer failure or maintenance, power to both
the UPS Inverter and static switch would be lost. Since the purpose of the
static bypass is to operate in the event of a downstream fault, the UPS
inverter would not be capable of responding to faults of this nature. It would,
however, continue to use battery power to feed the loads until the batteries
were fully discharged.
Because most UPS battery systems are not intended to
provide long periods of standby power under the aforementioned condition,
resumption of Normal power from the “SUS-F1A” switchgear would need to be done
quickly. This may be difficult as personnel would need to first open the 4000 A
“MB-F1A” main breaker. They would then need to manually operate the Key
Interlock Scheme to enable a second source, such as the 2000 kW generator or
the tie breaker to the other half of the double-ended switchgear.
To ensure a
quick resumption of power, transfer switches are also used in a number of
healthcare and mission critical applications to automatically connect to an
alternate source should main power fail. While UPSs are traditionally used to
back up sensitive servers and data processing equipment, there are many other
places they are utilized. In healthcare, they ensure a continuous source of reliable
power is available for electronic imaging equipment.
Larger kVA UPSs are used
in industrial applications such as microprocessor chip manufacturing
operations. They are also used to power ultraviolet purification equipment at
fresh water pumping stations.
In a data center application, a UPS may be used
to feed power to one or more power distribution units (PDUs). These PDUs are
similar in functionality to an IFS Switchboard. They incorporate an integral transformer
to step down the incoming 480 V UPS feed to a 208/120 V supply. The end utilization
voltage is distributed through integrated panelboards out to the various
computer loads. Individual circuits have CTs so each can be monitored on the
common touchscreen display.
Eaton PDUs can be provided in a variety of configurations including other larger frame breakers that can feed remote power panels (RPPs).
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| Figure 1.1-18. Power Distribution Unit |
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