Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1995-09-17
1998-03-03
Sircus, Brian
Electricity: motive power systems
Induction motor systems
Primary circuit control
318811, 187293, B06B 128
Patent
active
057239681
ABSTRACT:
A variable speed elevator drive system for automatically discriminating between large and small loads, and for adjusting a maximum cage speed (maximum output frequency) in accordance with such load. The system comprises a voltage detection circuit 4, a current detection circuit 5, and a CPU 6A which discriminates between large and small loads by a value I2 obtained by averaging a detected current I for a current detection range and current detection period that are provided as parameters, and automatically adjusts the maximum output frequency by determining a regenerative or power running state from the detected voltage and current. By making variable the current detection range and period, and a first order lag filter time constant used in averaging the current, an optimal maximum output frequency corresponding to the load may be selected to improve the operating efficiency even when fluctuations in the load are large. Further, by limiting a speed increase in the regenerative state, it is possible to prevent a dangerous operation such as descending with the speed being increased when the elevator is accelerated in a regenerative state.
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Mitsubishi Denki & Kabushiki Kaisha
Sircus Brian
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