Elevator Motor Speed Detection via Phase Short-Circuit Current
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Solution Overview
Problem
In emergency situations, elevator operators lack information about the speed of the elevator car, making manual movement unsafe and potentially damaging to the elevator, due to the absence of speed data during power failures or system failures.
Innovation Solution
A method to determine the speed of an electric motor in an elevator by forming an effective short-circuit between phases of the motor, measuring the short-circuit current, and using this data to calculate the speed, which can be communicated to operators or safety systems to control the elevator's movement safely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual operation of the elevator car is performed without speed information, then the operator can control the elevator movement, but the safety and comfort of individuals inside the car deteriorates due to lack of speed monitoring
Solution Approach 1:
The patent implements a feedback mechanism by measuring the actual speed of the elevator car during manual operation and providing this information to the operator. Speed sensors detect the car's velocity, and this data is displayed to the operator, enabling informed control decisions and ensuring safety during emergency manual operation.
2Ease of operation
If manual operation without speed information is used, then the operator can move the elevator car, but the risk of damaging the elevator increases due to unawareness of movement characteristics
Solution Approach 1:
The system provides real-time speed feedback to the operator during manual operation, enabling the operator to monitor movement characteristics and adjust control actions to prevent damaging speeds or abnormal movements that could harm the elevator system.
3Reliability
If speed measurement system is implemented, then safety and control information is provided to operators, but the device complexity increases due to additional sensors and measurement equipment
Solution Approach 1:
The patent utilizes the existing motor phases and current measurement infrastructure to derive speed information. The system processes signals already present in the motor control circuitry, eliminating the need for separate dedicated speed sensors in many cases, thus reducing overall system complexity while maintaining safety functionality.
4Measurement precision
If effective short-circuit is formed between motor phases to determine speed, then accurate speed information is obtained, but additional electrical components and control logic are required
Solution Approach 1:
The electrical drive system performs multiple functions: it controls motor operation, protects against faults, and simultaneously measures speed during manual operation by analyzing current signals from motor phases. This multi-functionality eliminates the need for separate dedicated speed measurement circuitry, reducing overall system complexity.
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 accurate speed information to operators, enhancing the safety of individuals inside the elevator and reducing the risk of damage to the elevator by enabling controlled and safe movement during emergencies.
Implementation Method 1
an electric motor (2), in this case a hoist motor, which in this case is a so-called permanent magnet motor of the synchronous motor type
Implementation Method 2
forming an effective short-circuit (4) between at least two of the plurality of phases (U, V, W) of the electric motor (2)
Data Source
Figure 1
Figure 2A~2B
Figure 3A~4C
AI summary
A method for determining a speed of an electric motor (2) of an elevator (100) comprising a plurality of phases (30A, 30B, 30C) for supplying electric current to the electric motor (2). The method comprises forming an effective short-circuit between at least two of the plurality of phases (30A, 30B, 30C) of the electric motor (2), determining a short-circuit current, the short-circuit current being the current flowing in the effective short-circuit, and determining the speed of the electric motor (2) based on at least one characteristic of the short-circuit current.