Semiconductor Dynamic Braking for PM Elevator Motors
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Solution Overview
Problem
Existing dynamic braking systems for permanent magnet electric motors in elevators are costly, large, and have limited lifetimes due to the use of mechanical switches with moving parts, posing safety risks during emergencies and requiring additional mechanical brakes for manual control.
Innovation Solution
A semiconductor-based dynamic braking system that eliminates the need for mechanical switches by using series-connected and anti-series-connected semiconductor devices to short-circuit motor windings, reducing size, cost, and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical switches (contactors) are used for dynamic braking, then the motor windings can be short-circuited to achieve braking, but the device size increases, cost increases, and lifetime is limited due to moving parts
Solution Approach 1:
The patent replaces mechanical contactors with semiconductor switches (IGBTs or MOSFETs) that have no moving parts. The semiconductor switches are arranged in bridge circuits connected to the motor windings, enabling electronic short-circuiting for dynamic braking without mechanical wear, thereby eliminating lifetime limitations and reducing device complexity.
Solution Approach 2:
The invention extracts and eliminates the mechanical switching component (contactors) from the dynamic braking system, retaining only the essential function of short-circuiting the motor windings through semiconductor devices. This removal of mechanical parts directly addresses the reliability and complexity issues.
2Reliability
If mechanical brakes are used simultaneously with dynamic brake, then emergency stopping capability is provided, but excessive deceleration occurs that poses safety risks
Solution Approach 1:
The patent implements feedback control by monitoring the motor current and back electromotive force during dynamic braking. The control system adjusts the semiconductor switch timing and duration based on real-time motor state, enabling precise control of deceleration rates and preventing excessive deceleration that would occur with uncoordinated mechanical and dynamic braking.
Solution Approach 2:
The invention transitions from static mechanical braking to dynamic, electronically controlled braking. The semiconductor switches can be rapidly switched on and off, allowing the braking force to be dynamically adjusted in real-time based on motor speed and load conditions, thereby achieving smooth and safe deceleration.
3Ease of operation
If manual mechanical brake operation is used during maintenance, then the elevator car can be lowered, but abrupt terminal stop with high velocity occurs posing safety risks
Solution Approach 1:
The patent enables the dynamic braking system to automatically assist during maintenance operations. When the service technician operates the mechanical brakes to lower the car, the semiconductor-based dynamic braking system automatically activates to provide controlled electrical braking, eliminating the need for purely manual operation and preventing abrupt stops.
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 semiconductor-based system prolongs the service life, enhances safety, and reduces space requirements while providing reliable dynamic braking without mechanical parts, improving elevator operation during emergencies and normal conditions.
Implementation Method 1
Each one of the phase legs comprises at least two series-connected semiconductor devices, such as semiconductor diodes or switches
Implementation Method 2
By short-circuiting the windings, the back electromotive force of the motor can be utilized to oppose the movement of the rotor and, thus, for dynamic braking of the motor
Data Source
AI summary
A method for dynamic braking of a permanent magnet motor, and an elevator utilizing thereof, are presented. The arrangement includes a corresponding number of phase legs and input connectors relative to a number of the plurality of motor windings, wherein each one of the input connectors is coupled to a respective one of the phase legs. At least some of the phase legs comprise at least two semiconductor devices. Second terminals of the phase legs are connected to each other, wherein the arrangement includes a number of semiconductor switches configured for forming a short-circuit between each of the plurality of motor windings.