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SC SERIES CURRENT TRANSFORMER

 

The Midwest SC Series

Features:

  • The Volt Ampere output is 1 or 2 VA.
  • Standard leads are 24" in length.
  • 600 Volt insulation is standard. A High-Voltage option is available at an additional cost.
  • Screw terminals available in place of leads.

Dimensions for SC Series (inches):

Dimensions for SC Series



Options for the SC Series:

  • Special Lead Lengths
  • Extra Taps


Installation:
CARE MUST BE TAKEN TO ENSURE THE SECONDARY LEADS ARE CONNECTED AT ALL TIMES when current is passing through the primary conductor.

Construction:
The Midwest current transformer core is made with grain oriented steel. The core is insulated and then wound with a secondary winding. The 24" leads are permanently fastened in place and the assembly is placed in a sealed case.

SC Series Ratio Modifications



Primary Turn Ratio Modifications

Formula:
Ka = Kn x Nn /Na
Where:
Ka = Actual Transformer Ratio
Kn = Nameplate Transformer Ratio
Na = Actual Number of Primary Turns
Nn = Nameplate Number of Primary Turns
The ratio of the current transformer can be modified by adding more primary turns to the transformer. By adding primary turns, the current required to maintain five amps on the secondary is reduced. (Example: A 100:5 current transformer designed for one primary turn.)
Square Case Transformer Polarity

   Square Case Transformer polarity     Square Case Transformer polarity

 

 

 

 

 

Secondary Turn Ratio Modification



The current ratio between the primary and secondary winding is defined by the following formula:
Ns x Is = N<p x Ip
Where:
Ip = Primary Current
Is = Secondary Current
Np = No. of turns on the Primary Winding
Ns = No. of turns on the Secondary Winding
The ratio of the current transformer can be modified by altering the number of secondary turns. Forward or backwinding the secondary leads through the window of the current transformer will add or subtract secondary turns respectively.

By adding secondary turns the same primary current will result in a decrease in secondary current output. By subtracting secondary turns the same primary current will result in greater secondary output.
 
Subtracting turns from a square case transformer
To subtract secondary turns, the lead from the X1 terminal should be would through the CT from the same side as H1.
Adding turns to a square case transformer
To add secondary turns, the lead from the X1 terminal should be wound through the CT from the side opposite H1.