Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
193 words
Induction motor drive apparatus of the type having a speed detector for detecting the rotational speed of an induction motors speed command means for producing a command speed, and an error amplifier for amplifying a difference between the rotational speed of the induction motor and the command speed, the induction motor being driven by so controlling the amplitude of the primary current as to vary the amplitude of the secondary current in accordance with the difference between the rotational and command speeds,'characterised in that the apparatus includes two-phase sinusoidal wave generating means for generating two sinusoidal signals displaced in phase from one another by π/2 and whose amplitudes conform to the output of.the error amplifier; primary load current arithmetic means for computing a primary load current by employing the output of the error amplifier and the output of said two-phase sinusoidal wave generating means; and primary current arithmetic means for computing a two-phase primary current command by adding the primary load current to the output of said two-phase sinusoidal wave generating means, which output serves as an excitation current; and means for driving the induction motor in accordance with the primary current command.
Claim 2
Dependent Claim
193 words
Induction motor drive apparatus of the type having a speed detector for detecting the rotational speed of an induction motors speed command means for producing a command speed, and an error amplifier for amplifying a difference between the rotational speed of the induction motor and the command speed, the induction motor being driven by so controlling the amplitude of the primary current as to vary the amplitude of the secondary current in accordance with the difference between the rotational and command speeds,'characterised in that the apparatus includes two-phase sinusoidal wave generating means for generating two sinusoidal signals displaced in phase from one another by π/2 and whose amplitudes conform to the output of.the error amplifier; primary load current arithmetic means for computing a primary load current by employing the output of the error amplifier and the output of said two-phase sinusoidal wave generating means; and primary current arithmetic means for computing a two-phase primary current command by adding the primary load current to the output of said two-phase sinusoidal wave generating means, which output serves as an excitation current; and means for driving the induction motor in accordance with the primary current command.
Claim 3
Dependent Claim
38 words
Apparatus according to claim 1, in which the error amplifier receives the difference between the command speed and the rotational speed of the induction motor for amplifying said difference and for executing a proportional integrating operation. or 2
Claim 4
Dependent Claim
115 words
3 . Apparatus according to claim 1/ in which the two-phase sinusoidal'wave generating means comprises: a voltage-to-frequency converter for generating pulses of a frequency which is proportional to the difference between the command speed and the rotational speed of the induction motor; a counter circuit for combining and counting said pulses and pulses of a frequency proportional to the rotational speed of the induction motor; function generators for generating two sinusoidal signals which differ in phase from one another by π/2 in accordance with the value of the count in said counter circuit; and multiplier circuits ' for multiplying the outputs of said function generators by the output of the error amplifier. 2 or 3,
Claim 5
Dependent Claim
130 words
Apparatus according to claim 11 in which the primary load current arithmetic means comprises: an inverter circuit for inverting the phase of one of the two sinusoidal signals, expressed by I m sin , from the two-phase sinusoidal wave generating means, thereby to deliver a sinusoidal signal expressed by -I m sin ; a first multiplier circuit for multiplying the output of the error amplifier by the other of the two sinusoidal signals, expressed by I m cos , from the two-phase sinusoidal wave generating means, thereby to deliver a sinusoidal signal expressed by I 1' cos ; and a second multiplier circuit for multiplying the output of the error amplifier by the output of said inverter circuit, thereby to deliver a sinusoidal signal expressed by -I 1' sin .
Claim 6
Dependent Claim
43 words
Apparatus according to claim 4, in which the primary current arithmetic means executes operations expressed by I m cos - I 1' sin , and I m sin - I 1 ' cos , thereby to deliver a two-phase primary current command signal.
Claim 7
Dependent Claim
58 words
Apparatus according to any preceding claim, which further comprises: a two-phase to three-phase converter circuit for converting a two-phase current command signal into a three-phase signal, and a pulse width modulator circuit for pulse-width modulating the output of the two-phase to three-phase converter circuit, the induction motor being driven by the output of said pulse width modulator circuit.