Procedure and apparatus for braking a squirrel-cage elevator motor fed by a frequency converter in fault situations
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United States of America Patent
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-
Jan 11, 1994
Grant Date -
N/A
app pub date -
Mar 7, 1991
filing date -
Mar 13, 1990
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A procedure and apparatus are provided for braking a squirrelcage elevator motor fed by a frequency convertor in fault situations using a direct current supplied from a d.c. voltage source. In the procedure of the invention, the current in at least one of the motor phases and the rotational speed of the motor are measured. When the elevator speed exceeds the value corresponding to the nominal slip and the motor current is less than the nominal magnetizing current, a switching device is caused to connect a direct current from a d.c. voltage source to the motor, thereby providing a magnetizing current and allowing the motor to act as an eddy current brake.
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