Electro Industries/GaugeTech Nexus 1250, Installation & Operation Manual

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Electro Industries/GaugeTech
Doc #: E107-6-07-121
7-4
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The following derivation equations give the above values in terms of known transformer and meter
parameters:
•
%LWFE (%) = 100 x (Watt Losses Iron (KW)/Primary KW)
•
%LWCU (%) = 100 x (Watt Losses Copper (KW)/Primary KW)
•
%LVFE (%) = 100 x (Var Losses Iron (KW)/Primary KVAR)
•
%LVCU (%) = 100 x (Var Losses Copper (KW)/Primary KVAR)
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The loss values of LWFE, LVFE, LWCU and LVCU are the actual losses used in computing the
percentages above. The equation for Primary KVA is:
•
Primary KVA = (Meter Secondary Voltage x VTR) x (Meter Secondary Current x CTR) x No.
Elements (3)
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The equation for Watt losses due to iron is:
•
LWFE = ((Meter Secondary Volts x VTR)/Rated Transformer Volts)
2
x No Load Loss Watts
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The equation for Var losses due to iron is:
•
LVFE = ((Meter Secondary Volts x VTR)/Rated Transformer Volts)
4
x No Load Loss Vars
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The equation for Watt losses due to copper is:
•
LWCU = ((Meter Secondary Current x CTR)/ Primary Current at Rated Bank KVA and Test
Phase Volts))
2
x Load Loss Watts
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The equation for Var losses due to copper is:
•
LVCU = ((Meter Secondary Current x CTR)/Primary Current at Rated Bank KVA and Test
Phase Volts))
2
x Load Loss Vars
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Test Phase Voltage and the Load and No Load Watts are provided by the transformer manufacturer.
All other information must be derived using the following equations, which are derived from the
information provided by the transformer manufacturer and from the Nexus Monitor specified by the
customer.
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The following equation gives Primary Current at Rated Bank KVA and Test Phase Voltage. This
value is used in calculating Copper Watt and Var losses, above.
•
Primary Current at Rated Bank KVA and Test Phase Voltage = (Bank KVA Rating/Test Phase
Voltage) x SQRT (3)
Courtesy of NationalSwitchgear.com