Pulse Transformer Working, Important Parameters, Advantages and Application

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Pulse Transformer

  • For coupling square wave or a pulse from primary to secondary the conventional transformer need change of shape of signal.
  • Pulse transformer is a transformer which is designed to couple pulses from primary to the load connected to secondary without changing the shape of the pulse.
  • Pulse transformers are used for coupling pulses from a low power digital circuit to a highpower SCR or Triac Circuit maintaining the isolation between them. 

Following are the Majour Features (Advantages) of Pulse Transformer. 

  1. Small and compact sizes. 
  2. High permeability alloy material is used for its core . Generally Ferrite cores of permalloys are used for this.
  3. The transformer winding has less no . of turns which results in small value of leakage reactance.
  4. Capacitance between windings is lower.
  5. Magnetizing inductance of such transformer is high.
  6. It has a high voltage insulation between its windings and earth (ground). 

Following Figure Represents Input – Output Wave Forms of a Pulse Transformers.

Following important parameters are to be considered.

  1. Overshoot : Amount by which the output voltage of pulse transformer exceeds it peak value (Vm) it is known as over shoot (see the Figure)
  2. Peak value (Vm) : Maximum value of pulse output without considering overshoot is known as peak value (Vm) 
  3. Rise time (Tr) : Time taken by the pulse output to raise 90 % of peak (Vm) value from 10 % value is a “Rise Time “Tr shall as small as possible. 
  4. Fall time (Tf ) : Decrease from peak (Vm) value to 10 % of  Vm in the time is a fall time. 
  5. Undershoot : The portion of the o.p voltage wave form which extends below the zero level is called as undershoot or “Back Swing “.
  6. Pulse width : The time interval between the successive instants corresponding to 50 %  Vm is called is pulse width.
  7. Droop : The reduction is pulse amplitude corresponding to the flat portion of the pulse is called as “Droop”. Droop is also called as “Sag” or Tilt. 
  • See these terms marked in the Figure

Applications of Pulse Transformer

  1. It is used as Isolation Transformer.
  2. Pulse amplitude circuit is used for triggering SCRs.
  3. This circuit is used in Radars and also in Cathod Ray Tubes (CRTS).
  4. It is used in control circuit.
  5. In microwave tube circuits.
  6. Used in pulse generating circuit.

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