Elevator Manual Emergency Braking Using Regenerative Motor Control
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Solution Overview
Problem
Traditional dynamic braking in elevator motors is not effective for all motor/load combinations, leading to instability and increased costs due to the need for oversized motors to compensate for inadequate braking torque.
Innovation Solution
An elevator system with a manual active dynamic braking function using a frequency converter, rectifier and inverter bridges, semiconductor switches, and a safety logic, which enables dynamic braking through a manual bypass switch and DC supply circuit powered by regenerative energy from the elevator motor during power outages, ensuring adequate torque based on the motor/load situation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional dynamic braking with mechanical contactor is used, then the system structure is simple, but the braking torque is inadequate and system stability deteriorates for certain motor/load combinations
Solution Approach 1:
The patent replaces the mechanical contactor-based dynamic braking system with an electronic control system using semiconductor switches (IGBTs) in the inverter bridge. This substitution eliminates the need for mechanical contactors and enables precise electronic control of braking torque through the drive controller, significantly improving braking effectiveness and system stability while maintaining acceptable complexity through integrated electronic components.
Solution Approach 2:
The patent changes the control parameters from fixed mechanical contactor operation to variable electronic control. The drive controller dynamically adjusts the switching signals to semiconductor switches based on motor speed, load conditions, and desired braking torque. This parameter variation enables adaptive braking control that maintains optimal performance across different motor/load combinations, resolving the stability issue.
2Reliability
If an oversized motor is used to compensate for inadequate braking torque, then the braking torque becomes adequate, but the cost increases
Solution Approach 1:
The patent enables the motor to serve dual purposes: propulsion during normal operation and dynamic braking during emergency stops. The same motor windings that generate torque during operation are used to generate regenerative braking torque when the motor operates as a generator. This self-service capability eliminates the need for oversized motors dedicated solely to braking functions, reducing system cost while ensuring adequate braking torque through intelligent control.
Solution Approach 2:
The patent changes the operational parameters of the motor from single-mode propulsion to dual-mode operation (motoring and generating). By controlling the semiconductor switches to reverse current flow direction and utilizing the motor's back-EMF during deceleration, the system generates sufficient braking torque from the existing motor size, avoiding the cost penalty of oversized motors while maintaining braking adequacy.
3Reliability
If safety logic cuts off control pulses during power outage, then safety is improved, but dynamic braking functionality is lost
Solution Approach 1:
The patent introduces a dynamic bypass switch that can change the state of the safety logic connection based on operational needs. During normal operation, the safety logic remains active and cuts off control pulses for safety. During manual emergency drive, the bypass switch dynamically alters the connection state to allow control pulses to reach the semiconductor switches, enabling dynamic braking while maintaining overall safety through the manual override mechanism and mechanical brake backup.
Solution Approach 2:
The patent introduces a bypass switch as an intermediary element between the safety logic and the drive controller. This intermediary can selectively connect or disconnect the control signal path based on the operational mode. During emergency manual drive, the bypass switch acts as a mediator that allows control pulses to pass through despite the safety logic's cutoff command, enabling dynamic braking functionality while preserving the safety logic's protective function for normal operations.
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
Provides stable and cost-effective dynamic braking during power outages and maintenance, enhancing safety and efficiency by utilizing regenerative energy without additional power sources, suitable for retrofitting existing elevators.
Implementation Method 1
a rectifier bridge (26) and an inverter bridge (32) with semiconductor switch circuits (70). The rectifier bridge (26) and inverter bridge (32) are connected via a DC link (34)
Implementation Method 2
an AC elevator motor (12), which is able to generate power in a generator mode
Implementation Method 3
The motor drive (22) further comprises a DC supply circuit (60) connected with the DC link (34), which DC supply circuit (60) is arranged to supply power at least to the drive controller (42) and to the bypass switch (56)
Data Source
Figure 1
Figure 2
AI summary
The invention relates to an elevator (10) comprising a manual active dynamic braking function, which elevator comprises an elevator control (46) for operating at least one elevator car (14) in at least one elevator driveway between landing floors in response to elevator calls, an AC elevator motor ( 12), which is able to generate power in a generator mode, a motor drive ( 22) connected to the elevator control (46) for the regulation of the speed of the elevator motor (14), comprising a frequency converter (24), whereby the frequency converter (24) of the motor drive ( 22) comprises a rectifier bridge (26) and an inverter bridge (32) with semiconductor switch circuits (70a - 70f), which rectifier bridge (26) and inverter bridge (32) are connected via a DC link (34), the motor drive ( 22) further comprising a drive controller (42) at least to control the semiconductor switches (72) of the semiconductor switch circuits (70a - 7 Of) of the inverter bridge (32) to regulate the elevator motor (12) to a reference speed, whereby the semiconductor switch circuits (70a - 70f) of the inverter bridge (32) are provided with diodes (74) connected anti-parallel to the semiconductor switches (72), the motor drive (22) comprises a safety logic (44) for cutting off control pulses to the semiconductor switches (72), at least during power outage, - at least one elevator brake (20a, 20b) is located in connection with the elevator motor ( 12) and/or with a traction sheave of the elevator motor (12), a manual brake release lever (50) is functionally linked (54) to the elevator brake (20a, 20b), movable between a rest position and at least one operating position to release the elevator brake (20a, 20b) manually. According to the invention the motor drive (22) comprises a bypass switch (56) being arranged to operate the safety logic (44), as to enable dynamical braking of the elevator motor (12) by connecting the semiconductors (72) of the semiconductor switch circuits (70a - 70f) of the inverter bridge (32) with the drive controller (42), and the motor drive (22) comprises a DC supply circuit (60) connected with the DC link (34), which is arranged to feed DC power at least to the drive controller (42) and to the bypass switch (56) to enable dynamic braking control of the semiconductor switches (72). The manual brake release lever (50) is functionally connected with the bypass switch (56) and (50) is arranged to operate the bypass switch (56), when it is moved away from its rest position. Alternatively the elevator (10) comprises a manual actuator (64), such as a key switch, disposed in the same location with the manual brake release lever (50), whereby the manual actuator (64) is arranged to operate the manual bypass switch (56).