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Scale Factor Setup
Scale Factor Setup
What is a scale
factor?
A scale factor is the ratio of the input to output for a particular current transformer (CT)
or potential transformer (PT). A scale factor is entered in the 4400 and then multiplied
automatically by the measured voltage or current so the unit displays the correct values,
as referenced to the primary side, rather than the secondary side of the PT or CT.
NOTE: If voltage and current connections are made without using any of the above
named devices, the scale factor should be set to 1.
When to use
Scale factors must be entered for the following conditions:
• A Dranetz
current probe is connected to a permanently installed CT.
• The current connections are made using a Dranetz
ISO box.
• The voltage connections are made using a PT.
Non-Dranetz
equipment
Refer to the CT name plate or to the manufacturer’s literature to determine the scale
factor.
Sample
calculation
The scale factor for a single CT or PT is calculated from its step-up or step-down ratio.
Example of step-down ratio
If a current transformer has a step-down ratio of 1000A:5A, therefore:
Scale Factor = 1000/5 = 200
Example of step-up ratio
If a potential transformer has a step-up ratio of 1V:10V, therefore:
Scale Factor = 1/10 = 0.1
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