This report is applicable to other and higher voltage grades when supply has been agreed by
Sales/Production.
3.0 Extension of Turn-off Time
This Report is applicable to other tq/re-applied dv/dt combinations when supply has been agreed by
Sales/Production.
4.0 Repetitive dv/dt
Higher dv/dt selections are available up to 1000V/µs on request.
5.0 De-rating Factor
A blocking voltage de-rating factor of 0.13%/°C is applicable to this device for Tj below 25°C.
6.0 Rate of rise of on-state current
DRM VDSM
V
V
RRM
V
V
RSM
V
V
D
DC V
V
R
DC V
The maximum un-primed rate of rise of on-state current must not exceed 1500A/µs at any time during
turn-on on a non-repetitive basis. For repetitive performance, the on-state rate of rise of current must not
exceed 1000A/µs at any time during turn-on. Note that these values of rate of rise of current apply to the
total device current including that from any local snubber network.
7.0 Square wave ratings
These ratings are given for load component rate of rise of forward current of 100 and 500A/µs.
8.0 Duty cycle lines
The 100% duty cycle is represented on all the ratings by a straight line. Other duties can be included as
parallel to the first.
9.0 Maximum Operating Frequency
The maximum operating frequency is set by the on-state duty, the time required for the thyristor to turn off
) and for the off-state voltage to reach full value (tv), i.e.
(t
q
1
=
max
f
++
vqpulse
ttt
Data Sheet. Types R0878LS16x to R0878LS21x Issue 1Page 3 of 12June, 2001
Page 4
WESTCODE
(
)
(
)
10.0 On-State Energy per Pulse Characteristics
These curves enable rapid estimation of device dissipation to be obtained for conditions not covered by
the frequency ratings.
Then the average dissipation will be:
Positive development in power electronics
be the Energy per pulse for a given current and pulse width, in joules
Let E
p
Let R
and T
be the steady-state d.c. thermal resistance (junction to sink)
th(J-Hs)
be the heat sink temperature.
SINK
R0878LS16x to R0878LS21x
11.0 Reverse recovery ratings
(i) Qra is based on 50% Irm chord as shown in Fig. 1 below.
is based on a 150µs integration time.
(ii) Q
rr
i.e.
=
.)(max
150
∫
0
µ
s
rrrr
125
Fig. 1
.
dtiQ
⋅−=⋅=
RWT and fEW
()
−
HsJthAVSINKPAV
1
t
(iii)
12.0 Reverse Recovery Loss
12.1 Determination by Measurement
From waveforms of recovery current obtained from a high frequency shunt (see Note 1, Page 5) and
reverse voltage present during recovery, an instantaneous reverse recovery loss waveform must be
constructed. Let the area under this waveform be E joules per pulse. A new heat sink temperature can
then be evaluated from:
where k = 0.227 (°C/W)/s
E = Area under reverse loss waveform per pulse in joules (W.s.)
f = rated frequency Hz at the original heat sink temperature.
= d.c. thermal resistance (°C/W).
R
th(J-Hs)
Data Sheet. Types R0878LS16x to R0878LS21x Issue 1Page 4 of 12June, 2001
FactorK
)()(
=
2
t
⋅+⋅−=
RfkETT
()
−
HsJthoriginalSINKnewSINK
Page 5
WESTCODE
The total dissipation is now given by:
12.2 Determination without Measurement
In circumstances where it is not possible to measure voltage and current conditions, or for design
purposes, the additional losses E in joules may be estimated as follows.
Let E be the value of energy per reverse cycle in joules (curves in Figure 9).
Let f be the operating frequency in Hz
Positive development in power electronics
(original)(TOT)
R0878LS16x to R0878LS21x
⋅+=
fEWW
()()
Where T
T
SINK (original)
A suitable R-C snubber network is connected across the thyristor to restrict the transient reverse voltage
to a peak value (V
67% of Grade, the reverse loss may be approximated by a pro rata adjustment of the maximum value
obtained from the curves.
NOTE 1
This thyristor has a low reverse recovered charge and peak reverse recovery current. W hen measuring
the charge care must be taken to ensure that:
R
- Reverse Recovery Loss by Measurement
(a) a.c. coupled devices such as current transformers are not affected by prior passage of high
amplitude forward current.
(b) A suitable, polarised, 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
(c) Measurement of reverse recovery waveform should be carried out with an appropriate critically
damped snubber, connected across diode anode to cathode. The formula used for the calculation
of this snubber is shown below:
2
4
SINK (new)
V
⋅=
⋅
C
S
is the required maximum heat sink temperature and
is the heat sink temperature given with the frequency ratings.
) of 67% of the maximum grade. If a different grade is being used or Vrm is other than
rm
r
di
dt
()
⋅⋅−=
fRETT
thoriginalSINKnewSINK
Where: Vr= Commutating source voltage
C
= Snubber capacitance
S
R= Snubber resistance
13.0 Gate Drive
The recommended pulse gate drive is 30V, 15Ω with a short-circuit current rise time of not more than
0.5µs. This gate drive must be applied when using the full di/dt capability of the device.
The duration of pulse may need to be configured with respect to the application but should be no shorter
than 20µs, otherwise an increase in pulse current could be needed to supply the resulting increase in
charge to trigger.
Data Sheet. Types R0878LS16x to R0878LS21x Issue 1Page 5 of 12June, 2001
Page 6
WESTCODE
p
p
14.0 Computer Modelling Parameters
14.1 Calculating VT using ABCD Coefficients
Positive development in power electronics
R0878LS16x to R0878LS21x
The on-state characteristic I
(i) the well established V
(ii) a set of constants A, B, C, D, forming the coefficients of the representative equation for V
terms of I
The constants, derived by curve fitting software, are given in this report for hot and cold characteristics
where possible. The resulting values for V
which is limited to that plotted.
14.2 D.C. Thermal Impedance Calculation
given below:
T
vs VT, on page 7 is represented in two ways;
T
and rs tangent used for rating purposes and
o
()
ln
agree with the true device characteristic over a current range,
T
125°C Coefficients
A1.510816
B-0.01749119
1
-4
-3
−
t
τ
p
−⋅=
err
C4.616469×10
D2.404072×10
=
np
∑
pt
=
p
1
in
T
⋅+⋅+⋅+=
IDICIBAV
TTTT
Where p = 1 to n, n is the number of terms in the series.
t = Duration of heating pulse in seconds.
= Thermal resistance at time t.
r
t
r
= Amplitude of pth term.
τ
= Time Constant of rth term.
D.C. Double Side Cooled
Term1234
r
p
τ
p
Term12345
r
p
τ
p
0.017719014.240625×10
0.70857810.14358330.036151962.130842×10
D.C. Single Side Cooled
0.039471640.010228378.789912×10
4.0900621.0789830.085309170.011287911.240861×10
-3
6.963806×10
-3
-3
4.235162×10
3.043661×10
-3
1.907609×10
-3
-3
-3
-3
Data Sheet. Types R0878LS16x to R0878LS21x Issue 1Page 6 of 12June, 2001
The information contained herein is confidential and is protected by Copyright. The i nformation may not be used or disclosed
except with the written permission of and in the manner permitted by the proprietors Westcode Semiconductors Ltd.
In the interest of product improvement, Westcode reserves the right to change specifications at any time without prior notice.
Devices with a suffix code (2-letter or letter/digit/letter combination) added to their generic code are not necessarily subject to the
conditions and limits contained in this report.
Data Sheet. Types R0878LS16x to R0878LS21x Issue 1Page 12 of 12June, 2001