C770L datasheet(7/14 Pages) IRI

7 / 14 page

INTERNATIONAL

www.rectifierindia.com

April 2011

INVERTER GRADE THYRISTOR

C770L

Let Ep be the Energy per pulse for a given current and pulse width, in joules

Let Rth(j-Hs) be the steady-state d.c thermal resistance (junction to sink)

And Tsink be the heat sink temperature.

Then the average dissipation will be:

WAV = Ep. F and T SINK(max.) = 125-(WAV. Rth(J-Hs))

14. Reverse recovery ratings

15. (1) Qra is based on 50% Irm chord as shown in Fig.1

16. (2) Qra is based on a 150us integration time i.e.

17. A suitable R-C snubber network is connected across the thyristor to restrict transient reverse

voltage to a peak value (V3) of 67% of the maximum grade.If a different grade is being used or V3

is other then 67% of grade,the reverse loss may be approximated by a pro rata adjustment of the

maximum value obtained from the curves.

NOTE 1-Reverse recovery Loss by Measurement

18. This thyristor has a low reverse recovered charge and peak reverse current. When measuring the

charge , care must be taken to ensure that:

(a) a.c. coupled device ssuch as current transformers are not affected by perior passage of high

amplitude forward current.

(b) A suitable, polarized, clipping circuit must be connected to the input of the measuring

oscilloscope to avoid overloading the internal amplifiers by the relatively high amplitude forward

current signal

of this snubber is shown below.

16.0 Computer Modelling Parameters

Calculating VT using ABCD Coefficients

The on-state characteristic IT VS VT, on page 7 represented in two ways;

(i) the well established VTO and rT tangent used for rating purposes and

(ii) a set of constants A, B, C, D, forming the coefficients of the representative equation for VT in terms of

IT given below:

VT=A+B.In(IT)+C.IT+D.IT

C770L Datasheet(PDF) 7 Page - Insel Rectifier India Pvt. Ltd.