Elevator Motor Dynamic Braking During Manual Brake Release
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Solution Overview
Problem
Traditional dynamic braking in elevator motors is not effective for all motor/load combinations, leading to inadequate braking torque and system instability, necessitating the use of oversized motors which increase costs.
Innovation Solution
The implementation of a manual active dynamic braking system in elevators, utilizing a motor drive with a frequency converter, rectifier bridge, inverter bridge, and safety logic, along with a manual bypass switch and DC supply circuit, allows for controlled dynamic braking during power outages by reconnecting semiconductor switches to generate torque matching the specific 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 becomes unstable for certain motor/load combinations
Solution Approach 1:
The patent applies dynamics by making the braking system adjustable and adaptive rather than fixed. The motor drive controller dynamically adjusts the braking torque based on feedback from current sensors and motor parameters, allowing the system to adapt to different motor/load combinations. The control system modifies switching frequencies and duty cycles in real-time to optimize braking performance for each specific situation.
Solution Approach 2:
The patent changes key operating parameters including switching frequency, duty cycle, and current limits to optimize braking torque for different motor/load combinations. The controller adjusts these parameters based on feedback from sensors and pre-stored motor characteristics, enabling the system to maintain stable and effective braking across various operating conditions without requiring mechanical reconfiguration.
2Reliability
If an oversized motor is used to ensure adequate braking torque, then braking reliability is improved, but costs increase
Solution Approach 1:
The patent implements feedback control by continuously monitoring motor current, speed, and position during braking operations. The controller uses this feedback information to adjust the braking torque in real-time, ensuring adequate stopping power without requiring an oversized motor. The feedback loop compares actual braking performance with target values and makes corrective adjustments to maintain optimal braking force.
Solution Approach 2:
The motor drive controller automatically determines the optimal braking parameters based on pre-stored motor characteristics and real-time operating conditions. The system self-adjusts the braking torque, switching frequency, and current limits without external intervention, enabling a properly sized motor to achieve reliable braking performance through intelligent control rather than physical oversizing.
3Ease of operation
If manual brake release lever is used to release brakes during power outage, then ease of operation is improved, but dynamic braking control is lost due to safety signal cutoff
Solution Approach 1:
The patent applies preliminary action by pre-storing motor characteristics, parameters, and control algorithms in the motor drive controller before a power outage occurs. The controller is pre-configured with safety logic and bypass capabilities that automatically activate when power is lost. This preliminary preparation enables the controller to maintain dynamic braking control even after the safety signal is cutoff, as all necessary data and control routines are already in place.
Solution Approach 2:
The patent introduces a bypass switch as an intermediary element that allows the motor drive controller to operate independently of the safety signal during power outages. The bypass switch acts as a mediator between the manual brake release lever and the control system, enabling the controller to receive alternative enable signals that permit dynamic braking control to continue functioning even when the normal safety signal path is interrupted.
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
This solution provides a stable and cost-effective dynamic braking function during manual emergency runs or power outages, ensuring adequate braking torque in all load situations without the need for extra reserve power, enhancing safety and reducing costs.
Implementation Method 1
a rectifier bridge (26) arranged to convert AC power from a public network (28) into DC power
Implementation Method 2
The semiconductor switch circuits of the inverter bridge are each provided with a semiconductor switch and an antiparallel diode
Implementation Method 3
the rotation of the motor causes EMF (electro motive force) voltage in the windings of the permanent magnet motor
Implementation Method 4
The brakes are electrically actuated via brake coils and a mechanical release lever
Data Source
AI summary
An elevator includes a manual active dynamic braking function, which elevator includes an elevator control for operating at least one elevator car in at least one elevator driveway between landing floors in response to elevator calls, an AC elevator motor, which is able to generate power in a generator mode, a motor drive connected to the elevator control for the regulation of the speed of the elevator motor, including a frequency converter, whereby the frequency converter of the motor drive includes a rectifier bridge and an inverter bridge with semiconductor switch circuits, which rectifier bridge and inverter bridge are connected via a DC link, the motor drive further including a drive controller at least to control the semiconductor switches of the semiconductor switch circuits of the inverter bridge to regulate the elevator motor to a reference speed, whereby the semiconductor switch circuits of the inverter bridge are provided with diodes connected anti-parallel to the semiconductor switches, the motor drive including a safety logic for cutting off control pulses to the semiconductor switches, at least during power outage, at least one elevator brake is located in connection with the elevator motor and/or with a traction sheave of the elevator motor, a manual brake release lever is functionally linked to the elevator brake, movable between a rest position and at least one operating position to release the elevator brake manually. The motor drive includes a bypass switch being arranged to operate the safety logic, as to enable dynamical braking of the elevator motor by connecting the semiconductors of the semiconductor switch circuits of the inverter bridge with the drive controller, and the motor drive includes a DC supply circuit connected with the DC link, which is arranged to feed DC power at least to the drive controller and to the bypass switch to enable dynamic braking control of the semiconductor switches. The manual brake release lever is functionally connected with the bypass switch and is arranged to operate the bypass switch, when it is moved away from its rest position. Alternatively, the elevator includes a manual actuator, such as a key switch, disposed in the same location with the manual brake release lever, whereby the manual actuator is arranged to operate the manual bypass switch.