bridge diode rectifier when the tfwrm is only driven as the generator the regulation transistor 90 is pwm switched in order to control a primary field current if 1 flowing through the primary field windings 30 u 30 v and 30 w connected in series the freewheeling diode 300 is connected in parallel to primary field windings 30 u 30 v and 30 w the rotor circuit 3000 shown in fig2 is the same as the rotor circuit shown in fig1 generator operation of the tfwrm shown in fig2 27 is explained as follows the primary field current if 1 is supplied to primary field windings 30 u 30 v and 30 w connected in series thus teeth 21 l of u phase stator cores 2 u teeth 21 r of v phase stator core 2 v and teeth 21 l of w phase stator core 2 w are magnetized to n poles thus a u phase voltage vu 2 a v phase voltage vv 2 and a w phase voltage vw 2 are induced across three secondary windings 60 u 60 v and 60 w respectively rectifier 600 a rectifies the three phase secondary voltage consisting of the u phase voltage vu 2 the v phase voltage vv 2 and the w phase voltage vw 2 and supplies the rectified field current if to field windings 6 u 6 v and 6 w therefore teeth 41 l and 41 r are magnetized it is desirable that teeth 41 l of u phase rotor cores 4 u teeth 41 r of v phase rotor core 4 v and teeth 41 l of w phase rotor core 4 w are magnetized to s.