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PROGRAM ROZWOJOWY

^1 POLITECHNIKI WARSZAWSKIEJ

a = U_a —

The maximum value of #_w, for Q_on = 0 (zero advance angle), is given by motor design:

(1.26)

where: 6_m - aligned position angle, N_r - number of rotor poles (teeth).

The base speed cOo corresponds to #_wmax and single voltage pulse Ud with maximum flux linkage ^/_max, which is dependent on machinę design and the level of saturation. Thus, to reach higher speeds co (above co*,), we have to saturate the magnetic Circuit of that machinę (Eąuation 1.25). This is called flux weakening.

The smaller the angle 0_off - 6_m, the smaller the negative torque "contribution" of the phase going off. In reality at 6= 6_m (aligned position) if the current i_m is already less than (25 -30%) of the peak current, the negative (generating) torąue influence becomes smali.

Once one phase is turned-off at 0_C another one is turned-on, eventually soon, to contribute positive torąue such that to lower the total torąue pulsations caused by the reduction of torąue in the phase going off.

It is now evident that the entire magnetic energy of each phase is "pumped" in and out for each conduction cycle. There are mN_r cycles per mechanical revolution. A part of this energy is passed over to the incoming phase through the power electronic converter (P.E.C.) and the rest to the DC bus filtering capacitor of P.E.C. Below base speed COo the current is limited (and controlled) through PWM (Fig. 1.10, Fig. 1.8).

i

KAPITAŁ LUDZKI

NAROOOWA STRATEGIA SPÓJNOŚCI

UNIA EUROPEJSKA

EUROPEJSKI FUNDUSZ SPOŁECZNY

Materiały dydaktyczne dystrybuowane bezpłatnie.

Projekt współfinansowany ze środków Unii Europejskiej w ramach Europejskiego Funduszu Społecznego

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