PULSE TRANSFORMERS - INTRODUCTION

Explanations

The pulse transformer (IT) is used above ali as drive module from the control electronics to the power part.
In almost aII applications a control pulse is transformed, galvanically separated, to the high voltage potentials.
Whether with the ignition ofthyristors end triacs or when driving modern components such as FET's or IGBT's,
the pulse transformer is used everywhere.
It is also used in telecommunications as a galvanic separating element in data transmission devices.
Compared with the solution using opto couplers a simplified switching structure and direct energy transfer are
possible (no auxiliary supply necessary). Pulse transformers have an almost unlimited Iife span, this is a further
major advantage compared with the optical solutions with relatively Iow MTBF values.

 


Definitions:

N          : turn ratio or voltage ratio between primary and secondary windings.


∫Udt     : voltage-time area (Vps)
              This is the product of impulse height and pulse width measured at half impulse height.


tr           : Pulse rise time (us)
              This time is measured from 10% + 90% of the pulse height.


If           : Firing current (A)
               Max. available pulse current.


LP          : Primary inductance (mH)
              Measured as per EN 60938 ( signal 0.1mA, tolerance -30 +50%).


Cc          : Coupling capacity (pF)
               Measured between primary and secondary winding.
               Is heavily dependent on the winding structure.


UR         : Maximum operating voltage (V).


UP         : Test voltage (kV)
              Measured between primary and secondary winding
              Also dependent on the winding structure.
              Measurement 100% in the final test (up to 3.5 kVAC for 2 seconds).


UG        : Glow discharge voltage (V)
              Determines the Iife expectancy of the IT's in operation with excessive operating voltage.
              At Ieast 50% higher than the max. operating voltage.


Pd         : Maximum power Ioss at 50°C ambient temperature.