Torque control systems of induction motors

A torque control system of an induction motor having m phase stator windings and P poles, comprising means for producing a predetermined torque instruction, means responsive to said torque instruction for generating and applying a phase n voltage V.sub.ns expressed by the following equation (1) to the stator windings of said induction motor to cause it to generate a torque corresponding to said torque instruction ##EQU154## and means for controlling a term V.sub.o in the following equation (2) so as to make said phase voltage V.sub.n to be equal to a permissible maximum value when said phase voltage exceeds said permissible maximum value, ##EQU155## where ##EQU156## I.sub.o :

• constant exciting current (ampere) of the stator windings, r.sub.s, r.sub.r, l.sub.r and l.sub.m :
• constants inherent to the induction motor,
• .theta.:
• rotor rotating angle (radians) of the induction motor, and
• I.sub.2 :
• instructed rotor current (ampere) corresponding to the torque instruction.

A torque control system of an induction motor having m phase stator windings and P poles, comprising means for producing a predetermined torque instruction, and means responsive to said torque instruction for generating and applying a phase n voltage V.sub.ns expressed by the following equation to the stator windings of said induction motor to cause it to produce a torque corresponding to said torque instruction, ##EQU157## where ##EQU158## I.sub.o =I.sub.oB when I.sub.oB .ltoreq.I.sub.oN, I.sub.o =I.sub.oN when I.sub.oB >I.sub.oN,

• I.sub.oB :
• constant base exciting current (ampere), ##EQU159## r.sub.s, r.sub.r, l.sub.r and l.sub.m :
• constants inherent to the induction motor,
• .theta.:
• rotor rotating angle (radian) of the induction motor,
• I.sub.2m :
• maximum rotor current (ampere),
• E:
• maximumm permissible voltage (volt) of the stator voltage generating means,
• .alpha.:
• constant (volt), ##EQU160## K.sub.T :
• constant.

A torque control system of an induction motor having m phase stator windings and P poles, comprising means for producing a predetermined torque instruction, means responsive to said torque instruction for generating and applying a phase n voltage V.sub.ns expressed by the following equation to the stator windings of said induction motor to cause it to produce a torque T.sub.e corresponding to said torque instruction ##EQU161## and means for controlling V.sub.o in the following equation (2) so as to make said phase voltage to be equal to a permissible maximum value when said phase voltage exceeds said permissible maximum value, ##EQU162## where ##EQU163## I.sub.o :

• variable exciting current (ampere) and I.sub.o =I.sub.oB when I.sub.oB .ltoreq.I.sub.oN
• I.sub.o =i.sub.oN when I.sub.oB >I.sub.oN,
• I.sub.oB :
• constant base exciting current (ampere), ##EQU164## r.sub.s, r.sub.r, l.sub.r and l.sub.m :
• constants inherent to the induction motor,
• .theta.:
• rotor rotational angle (radian) of the induction motor,
• I.sub.2m :
• maximum rotor current (ampere),
• E:
• permissible maximum value of V.sub.ns (volt),
• .alpha.:
• constant (voltage), ##EQU165## K.sub.T :
• constant.