Resistive Shunts

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Resistive Shunts

There are various types of resistive shunts used in “Impulse current measurements”.

Such shunts are :

  1. Low ohmic resistive shunt
  2. Bifilar flat-strip type resistive shunt
  3. Co-axial Tubular / Park shunt
  4. Co-axial squirrel cage type resistive shunt

Characteristics of such shunts and their limitations

  1. Low ohmio resistive shunt : Large dimentions and hence it has residual inductance (L) and terminal capacitance (C). There ellest is much more when frequency is 1M or more Resistance value is in between 10µΩ to few mΩ.
  2. Bifilar flatstrip type : Resistance elements are wound in appenite direction and folder back UME co-axial connector is used. The drawback in such type in that it suffers from w inductance.
  3. Coaxial Tuber Park shunt : The draw back in Biflar type is over-come in this type. Maximum frequency limit is 1000 MHz and response time is few nanoseconds. Current pickup capacity upto 500 Kilo Amps. Voltage drop across shunt is about 100 Volts. This type puffers from skin effect. Heat dissipation limit is small due the large thickness of wall tube.
  4. Squirrel cage co-axial shunt : The draw backs in co-axial tuber type are eliminated in squirel cage type construction.

Thick rods or strips are used instead of thick tubes. Due to the use of round rods the construction looks like squirrel cage rotor construction of double cage induction motor.

This shunt shows peakly response for step-input. A compensating network provides optimum response. Some of such shunts user to measure impulse current are explained in more details in the following articles :
Such measurement can be done by various shunts such as,
  1. Bifilar flat strip type
  2. Coaxial tube type (Park’s shunt)
  3. Co-axial squirrel cage type.
  • One such Bifilar flat strip type is explained in brief :

[Figure A shows schematic diagram and Figure B shows connection diagram]

Bifilar Flat strip Resistive Shunt
Note in figures the parts. 
  1. Metal base
  2. C1, C2 current terminals of shunt
  3. Bifilar resistance strip
  4. Bakelite insulating spacers
  5. Co-axial UHF connectors.
  6. P1 and P2 potential terminals of shunt. 
  • The voltage signal is picked up through a ultra-high frequency UHF coaxial connector.
  • The resistance elements are wound in opposite directions and are folded back side, with both ends insulated by Bakelite. 
  • The shunt suffers from stray inductance associated with the resistance element, and its potential leads P1 and P2 are linked to a small part of magnetic flux generated by the “current” that is to be measured.

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