Issue:
How do you select a CT or  VT (current transformer or voltage transformer)?

Product Line:
measurement transformers

Environment:
Class 4210 instrument Transformers

Resolution:
Will need the following information to make a proper selection:

How to Select a Current Transformer
1. Determine that the primary range of the current transformer encompasses the application
requirement. Lower or specialized ratios may be obtained by adding primary and secondary turns
as shown on page 52 of the attached.

2. Select the proper window size or slightly larger to fit your primary conductor. Refer to the table on page 3.

3. Determine the usual application of the current transformer that best suits the application for which it is
intended. Refer to the table below. If the application requirements are not fully defined, refer to
“Burden and Accuracy Information” on page 53 of the attached document.

4. After selecting a transformer, check its accuracy and burden capabilities by referring to the .
The information page for that transformer is in the attached document.

How to Select a Voltage Transformer:
Square D offers three models of voltage transformers, each suited for a particular application. Model 450R is
designed for applications requiring accurate voltage measurement within the 0.3% accuracy class. Model 450R
is ideal for switchboard use with 1% instrumentation.

Model 460R is designed for voltage indication where accuracy is less critical or where burden requirements are
low. Model 460R is ideally suited for use with transducers and panelboards, and other monitoring applications.

Model 470R is designed for extremely accurate voltage measurement, which requires a very low burden.
Examples of such applications include the input to PLC modules and other electronic devices with a high input
impedance.

Please refer to the selection chart on page 3 as well of the attached document.

Released for: Schneider Electric USA