Elevator Carrier Frequency Switch Circuit for Overload Protection
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Solution Overview
Problem
Elevator control devices face challenges in efficiently managing torque and current during overloaded operations, leading to increased costs and size due to insufficient capacitance in inverter devices, and existing techniques do not effectively balance carrier frequency and torque to prevent damage to switching elements.
Innovation Solution
The elevator control device includes a motor controller, a carrier frequency switch circuit, and a power converter that dynamically adjusts the carrier frequency based on torque and current limits, allowing for continuous operation without damaging switching elements by automatically decreasing the carrier frequency when torque or current reaches predefined limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inverter device is selected with sufficient capacitance to handle overloaded test operation, then the elevator can perform overload tests, but the cost and size of the inverter device increase
Solution Approach 1:
The patent applies dynamic carrier frequency adjustment based on operating conditions. During normal operation, a higher carrier frequency is used for noise reduction, but during overloaded test operation, the carrier frequency is dynamically decreased to allow the inverter to deliver higher torque and current without requiring excessive capacitance, thus avoiding increased inverter size and cost
Solution Approach 2:
The patent changes the carrier frequency parameter dynamically based on the operating state. By detecting overload conditions and adjusting the carrier frequency accordingly, the system optimizes the balance between noise reduction and current capacity, allowing the same inverter hardware to handle both normal and overloaded operations without requiring oversized capacitance
2Power
If the carrier frequency is decreased to allow higher torque and current, then the inverter can produce more torque with invariable capacitance, but the noise reduction benefit is reduced
Solution Approach 1:
The system dynamically adjusts the carrier frequency based on operating conditions. During normal operation, high carrier frequency maintains noise reduction. During overloaded conditions, the carrier frequency is dynamically decreased to enable higher torque and current delivery, optimizing the trade-off between noise and power output for each operational state
Solution Approach 2:
The control system periodically monitors operating conditions and switches between different carrier frequency levels. This periodic adjustment allows the system to maintain optimal performance for each operational phase, switching from noise-optimized mode during normal operation to power-optimized mode during overloaded conditions
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 enables continuous elevator operation within safe parameters for switching elements, enhancing protection and flexibility while maintaining a balance between noise reduction and current capacity.
Implementation Method 1
the power converter performs PWM control based on the voltage command and the carrier frequency signal
Data Source
AI summary
An elevator control device includes a vector controller that calculates a voltage command required for driving an elevator cage, a carrier frequency switch circuit that outputs a carrier frequency signal, and a power converter that performs PWM control based on the voltage command and the carrier frequency signal, generates an AC power and supplies the AC power to an AC motor. The carrier frequency switch circuit changes the carrier frequency signal when a torque command for driving the AC motor reaches a torque limit value. Thus, it is possible to continuously operate an elevator without causing damage to a switching element of the power converter.