Elevator Brake Failure Detection Using Motor Back-EMF
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Solution Overview
Problem
Existing elevator systems face safety hazards due to delayed activation of auxiliary braking devices, which can lead to prolonged travel distances and increased risks of crashes when the primary braking device fails, especially near top and bottom stations.
Innovation Solution
A device comprising a primary braking device, an auxiliary braking device, a safety function control unit, and a switching device that determines the activation of the auxiliary braking device based on the magnitude of back electromotive force of the elevator motor, with optional features including relays and an overspeed switch to ensure timely activation of the auxiliary braking device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the auxiliary braking device is activated only by an overspeed switch of a speed governor, then the device complexity is reduced, but the response time is delayed and safety is compromised
Solution Approach 1:
The patent monitors the back electromotive force of the elevator motor continuously during operation, enabling early detection of primary braking device failure before the elevator reaches overspeed conditions. This preliminary monitoring allows the auxiliary braking device to be activated in advance, eliminating the delayed response inherent in traditional overspeed-switch-only systems and directly addressing the safety-time contradiction.
2Reliability
If the auxiliary braking device is activated based on back electromotive force monitoring, then the response time is improved and safety is enhanced, but the device complexity increases
Solution Approach 1:
The patent utilizes the back electromotive force generated by the elevator motor during normal operation as the monitoring parameter. The existing motor's back EMF serves dual purposes: normal motor operation and failure detection of the primary braking device. This self-service approach eliminates the need for separate sensors or additional monitoring equipment, thereby enhancing safety while minimizing the increase in device complexity.
3Loss of time
If the switching device couples the elevator motor with the safety function control unit immediately after primary braking device de-energization, then the response time is improved, but electromagnetic interference may affect control accuracy
Solution Approach 1:
The patent introduces a delay period after the primary braking device is de-energized before coupling the elevator motor with the safety function control unit. This preliminary delay allows electromagnetic transients to subside, ensuring that subsequent back electromotive force measurements are accurate and not corrupted by transient interference, thus balancing response time with measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables early detection of primary braking device failure and timely activation of the auxiliary braking device, reducing the risk of overspeed and crashes by using back electromotive force as a parameter, thereby enhancing elevator safety.
Implementation Method 1
a coil in a brake electromagnet has current passing through, and the electromagnetic core is magnetized and absorbed rapidly, driving a brake arm to make the brake tile and the brake wheel completely detach
Implementation Method 2
since there is no attraction between electromagnetic cores, a brake component will hold a brake wheel tightly under pressure of a brake spring, thus ensuring that the motor does not rotate
Implementation Method 3
configured to determine whether to activate the auxiliary braking device based on magnitude of back electromotive force of the elevator motor
Data Source
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AI summary
The present application relates to elevator safety technology, in particular to a device and method for implementing an elevator safety function. According to an aspect of the present application, there is provided a device for implementing an elevator safety function, comprising: a primary braking device configured to perform a holding brake operation when being de-energized; an auxiliary braking device configured to perform a holding brake operation when being de-energized; a safety function control unit selectively coupled with an elevator motor and configured to determine whether to activate the auxiliary braking device to perform the holding brake operation based on magnitude of back electromotive force of the elevator motor; and a switching device configured to couple the elevator motor with the safety function control unit after the primary braking device is de-energized.