Electrotechnical Systems

182 Electrotechnical Systems

FR block diagram is shown in Figure 5.21 [2]. The controller is PI type. Its gains

are decreasing with the help of divider when the speed ω is above the rated ω

n

. At

the FR input, the reference of the rated excitation current I

fn

and the largest of two

signals—the excitation current I

f

and emf k

m

E—are compared; moreover, the scale

of emf is xed so that under ω

n

and I

fn

the signals I

f

and k

m

E are numerically equal.

While k

m

E < I

fn

(up to ω

n

), a current control is active; during an increase in speed k

m

E

becomes more than I

f

and emf control (keeping up rated value emf) is active.

Model5_4 simulates this electrical d ...