Method and device for operating an induction machine

Claim 1

Device for operating an induction machine (33) via a self-commutated inverter (30, Q1-Ql), (a) which exhibits a flux conducting circuit for controlling the inverter, (b) the flux conducting circuit exhibiting a first comparator (46, V1) for comparing m first actual flux value components (ψ 1 -ψ 3 ; ψ 11 -ψ 1m ) of the induction machine (33) with at least one nominal flux value (ψ s ), m=the number of phases, (c) m first comparator output signals (K11-K13) produced by this comparison being supplied via a signal converter (36) to the inverter (30), wherein (d) the output of the first comparator (46, V1) is control-connected, on the one hand, via a phase shifter device (47, 98) to a selection circuit (48, 99) for a phase shift of 180°+180°/m and (e) on the other hand, via at least one logic circuit (Y, Y21-Yp-1) to this selection circuit, (f) the output of the selection circuit is effectively connected to the signal converter (36), (g) at least one second coordinate converter (56, KW1, KW2, KW2') is provided which supplies m second actual flux value components (ψ.sub.β1' -ψ.sub.β3' ; ψ.sub.β11' -ψ.sub.β1m', ψ.sub.β2m -ψ.sub.β2m'), which are phase shifted by a predeterminable angle (ψ) with respect to these m first actual flux value components (ψ.sub.β1 -ψ.sub.β3 ; ψ.sub.β11 -ψ.sub.β1m), to at least one second comparator (57, V1', V2') which compares these second actual flux value components with the at least one nominal flux value (ψ s ), (h) m second comparator output signals (K11'-K1m', K21'-K2m') produced by this second comparator are supplied to the at least one logic circuit, (i) the logic circuit exhibits elements (63-73) for logically combining the first and second comparator output signals in accordance with the following relation: ##EQU4## for j=3 . . . p.

Claim 7

A method for operating an induction machine that is fed via a self-controlled inverter having q≧2 voltage stages and m≧2 phases, comprising the steps of: generating for each phase of the induction machine at leat one first phase flux component and a second phase flux component phase shifted with respect to said first phase flux component by a predeterminable flux shift angle=180°/(2 p ·m) where p is an integral number≧1; monitoring each first and second phase flux component in a comparator for exceeding of a predeterminable flux limit value; shifting in phase by 180°+180°/m all comparator output signals obtained from the first flux components; forming at least one zig-zag signal in dependence on comparator output signals derived from the first and second phase flux components in accordance with the relations: ##EQU5## for j=3 . . . p; and using all said comparator output signals obtained from the first flux components, in dependence on said at least one zig-zag signal, for controlling the inverter, whereby the trajectory of the flux vector of the induction machine is conducted along an edge path having at least 2 p ·q·m edges, the flux vector of the induction machine being alternatingly conducted on straight segments and zig-zag segments along the edge path, the envelope curve of each zig-zag segment forming an edge of the edge path.

Claim 8

A method for operating an induction machine that is fed via a self-controlled inverter having q≧2 voltage stages and m≧2 phases, comprising the steps of: generating for each phase of the induction machine at leat one first phase flux component and a second phase flux component phase shifted with respect to said first phase flux component by a predeterminable flux shift angle=180°/(2 p ·m) where p is an integral number≧1; monitoring each first and second phase flux component in a comparator for exceeding of a predeterminable flux limit value; shifting in phase by 180°+180°/m all comparator output signals obtained from the first flux components; forming at least one zig-zag signal in dependence on comparator output signals derived from the first and second phase flux components in accordance with the relations: ##EQU5## for j=3 . . . p; and using all said comparator output signals obtained from the first flux components, in dependence on said at least one zig-zag signal, for controlling the inverter, whereby the trajectory of the flux vector of the induction machine is conducted along an edge path having at least 2 p ·q·m edges, the flux vector of the induction machine being alternatingly conducted on straight segments and zig-zag segments along the edge path, the envelope curve of each zig-zag segment forming an edge of the edge path.