S01

S02

Va

Vb

Vc

0

1

1

0

0

0

1

1

−Uc/6

Uc/2

Uc/6

−Uc/2

−Uc/6

−Uc/2

Uc/6

Uc/2

−Uc/3

0

−Uc/3

0