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Doc ID 3579 Rev 3

Case 2

Winding is switched on whereas a remanent negative induction remains on magnetic core.

According to Equation 8, for t = 0, we have then:

Equation 11

So

Equation 12

Figure 12 shows the maximum induction difference between two triggering methods

according to previous remanent induction.

When the first half-cycle conduction is the same polarity as the previous one, the induction

reaches a maximum which can be the double of the induction when triggering in reverse

polarity compared to remanent induction.

In the first case saturation can be reached very rapidly and the load behaves like a short

circuit. The peak current is limited only by the series resistance of the load.

Such phenomenon mainly occurs with transformers where the remanent induction can be

very high.

Figure 12.

Induction at beginning of conduction according to remanent induction

r

n

0

r

0

n

B

B

B

B

B

B

B(0)

−

=

→

−

=

+

−

=

r

B

n

B

)

2

ð

t

·sin(

ù

n

B

B(t)

−

+

−

=

⇒