WESTCODE An IXYS Company

Medium Voltage Thyristor Type K1351V#600-650

9.3 Calculating VT using ABCD Coefficients

The on-state characteristic IT vs. VT, on page 6 is represented in two ways;

(i) the well established VT0 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 ⋅ ln(IT )+ C ⋅ IT + D ⋅ IT

The constants, derived by curve fitting software, are given below for both hot and cold characteristics. The

resulting values for VT agree with the true device characteristic over a current range, which is limited to

that plotted.

25°C Coefficients

A 2.974069977

B -0.3289658

C 2.412020×10-4

D 0.03081106

115°C Coefficients

A -0.149843723

B 0.3620034

C 8.160760×10-4

D -0.03645489

10.0 Snubber Components

When selecting snubber components, care must be taken not to use excessively large values of snubber

capacitor or excessively small values of snubber resistor. Such excessive component values may lead to

device damage due to the large resultant values of snubber discharge current. If required, please consult

the factory for assistance.

11.0 Reverse recovery ratings

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

(ii) Qrr is based on a 150µs integration time i.e.

150 µs

∫Qrr = irr .dt

0

(iii)

K

Factor

=

t1

t2

Fig. 1

12.0 Duty cycle lines

The 100% duty cycle is represented on the frequency ratings by a straight line. Other duties can be

included as parallel to the first.

Provisional Data Sheet. Type K1351V#600 to K1351V#650 Issue 1

Page 5 of 11

May, 2005