AC elevator control system

Claim 2

An AC elevator control system comprising an elevator car and a counter weight connected to both ends of a traction rope respectively, a sheave over which said traction rope is trained, an induction motor for driving said sheave, a converter for converting an AC power to a direct current, an inverter for inverting said direct current from said converter to an AC power with a variable voltage at a variable frequency to supply said AC power to said induction motor, a battery connected across the DC side of said inverter and forming an electric source for actuating said inverter upon the occurrence of a power failure and/or a fault and a command emergency frequency generator responsive to the occurrence of a power failure or fault for delivering a low frequency command emergency signal to said inverter so as to not generate regenerative power with said inductive motor; wherein said command emergency frequency signal from said command emergency frequency generator, is set to a value as determined by the relationship between a difference in weight between said elevator car and said counter weight and various losses of a system for driving said induction motor.

Claim 3

An AC elevator control system as claimed in claim 1, wherein said command emergency frequency signal from said command emergency frequency generator is set to such a value that said inductor motor rotates at a rotatinal speed ω such that ω×T.sub.l <L.sub.m +L.sub.w +L.sub.f where T l designates an unbalanced load torque due to a difference in weight between said elevator car and said counter weight, ω×T l designates a mechanical input per unit time calculated in terms of a rotary shaft of said induction motor, L m designates a mechanical loss per unit time occurring on gears and other elements disposed on a hoist, L w designates a resistance loss per unit time resulting from currents flowing through a primary and a secondary winding of said induction motor, and L f designates an iron loss per unit time occurring on an iron core and other magnetic elements of said induction motor in a rotary magnetic field established within said induction motor.

Claim 4

An AC elevator control system comprising an elevator car and a counter weight connected to both ends of a traction rope respectively, a sheave over which said traction rope is trained, an induction motor for driving said sheave, a converter for converting an AC power to a direct current, an inverter for inverting said direct current from said converter to an AC power with a variable voltage at a variable frequency to supply said AC power to said induction motor, a battery connected across the DC side of said inverter and forming an electric source for actuating said inverter upon the occurrences of a power failure and/or a fault and a command emergency frequency generator responsive to the occurrence of a power failure or fault for delivering a low frequency command emergency signal to said inverter so as to not generate regenerative power with said inductive motor; wherein said command emergency frequency generator includes a pulse oscillator for generating a train of pulses having a constant pulse repetition frequency, a counter supplied with said train of pulses from said pulse oscillator and a count direction changing signal used to pulse-modulate said pulses supplied thereto, a decoder connected to said counter, and a plurality of "OR" gates a connected to said decoder producing said command emergency frequency signal; and wherein said command emergency frequency signal from said command emergency frequency generator, is set to a value as determined by the relationship between a difference in weight between said elevator car and said counter weight and various losses of a system for driving said induction motor.

Claim 5

An AC elevator control system comprising an elevator car and a counter weight connected to both ends of a traction rope respectively, a sheave over which said traction rope is trained, an induction motor for driving said sheave, a converter for converting an AC power to a direct current, an inverter for inverting said direct current from said converter to an AC power with a variable voltage at a variable frequency to supply said AC power to said induction motor, a battery connected across the DC side of said inverter and forming an electric source for actuating said inverter upon the occurrences of a power failure and/or a fault and a command emergency frequency generator responsive to the occurrence of a power failure or fault for delivering a low frequency command emergency signal to said inverter so as to not generate regenerative power with said inductive motor; wherein said command emergency frequency generator includes a pulse oscillator for generating a train of pulses having a constant pulse repetition frequency, a counter supplied with said train of pulses from said pulse oscillator and a count direction changing signal used to pulse-modulate said pulses supplied thereto, a decoder connected to said counter, and a plurality of "OR" gates a connected to said decoder producing said command emergency frequency signal; and wherein said command emergency frequency signal from said command emergency frequency generator, is set to a value as determined by the relationship between a difference in weight between said elevator car and said counter weight and various losses of a system for driving said induction motor.

Claim 6

An AC elevator control system as claimed in claim 3, wherein said command emergency frequency signal from said command emergency frequency generator is set to such a value that said inductor motor rotates at a rotational speed ω such that ω×T.sub.l <L.sub.m +L.sub.w + L.sub.f where T l designates an unbalanced load torque due to a difference in weight between said elevator car and said counter weight, ω×T l designates a mechanical input per unit time calculated in terms of a rotary shaft of said induction motor, L m a mechanical loss per unit time occurring on gears and others disposed on a hoist, L w a resistance loss per unit time resulting from currents flowing through a primary and secondary winding of said induction motor, and L f designates an iron loss per unit time occurring on an iron core and others of said induction motor in a rotary magnetic field established on said induction motor.