FLC21 FAMILY

5/6

RS RESISTANCE CALCULATION

The Rs resistance allows, in addition with the

capacitance C, to adjust the spark frequency and

to limit the current supplied by the mains. This

resistance allows the thyristor triggering in any

requested cases. In worst cases, the system must

fire when the a.c. line voltage is minimum while the

FLC are maximum.

The maximum Rs value is equal to:

Rs

VV

T T

kI

AC

BO

amb

BO

max

(

min.

)

[

max .(

.(

))]

.*

=

−+

−

21

25

α

* : see fig 1

10

12

15

18

22

27

33

39

47

10

20

30

50

F (Hz)

Rs (k )

Ω

Vac=100Vrms, Vbo=75V, Tamb=25

°C

C=1

F

µ

C=1

F

µ

C=1.5

F

µ

C=1.5

F

µ

C=2.2

F

µ

C=2.7

F

µ

C=3.3

F

µ

FLC21-65A

10

12

15

18

22

27

33

39

47

10

20

30

50

FLC21-135A

Vdc=300V, Vbo=150V, Tamb=25

°C

F (Hz)

Rs (k )

Ω

C=3.3

F

µ

C=2.7

F

µ

C=2.2

F

µ

C=1

F

µ

C=1

F

µ

C=1.5

F

µ

C=1.5

F

µ

Fig. 4: Spark frequency versus Rs and C

The couple Rs/C can be chosen with the previous

curve. Keep in mind the Rs maximum limit for

which the system would not work when the AC

mains is minimum.