DC Motor Drive Arrangement with H-Bridge for EMI Reduction
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Solution Overview
Problem
Conventional drive arrangements for automatic door operators using DC motors face challenges in minimizing electromagnetic interference (EMI) and power losses, particularly due to high switching frequencies, which can cause disturbances in electrical equipment and require complex calibration procedures when replacing motors.
Innovation Solution
A drive arrangement comprising a DC-motor, a H-bridge, and a controller that switches between active and pause states based on measured DC-motor current, using a H-bridge with a first and second voltage supply line, and upper and lower leg switches, allowing for reduced switching frequency and EMI by activating only necessary switches, thereby reducing wear and eliminating the need for complex calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high switching frequency is used in PWM control of DC-motor, then power losses are minimized and control precision is improved, but electromagnetic interference (EMI) increases causing disturbances in electrical equipment
Solution Approach 1:
The patent applies periodic action by implementing a pause state in the PWM control sequence where all switches are turned off temporarily. This periodic interruption of the control signal reduces the effective switching frequency, thereby minimizing EMI while maintaining adequate motor control. The pause state allows the motor current to settle and reduces the generation of electromagnetic disturbances in the surrounding electrical equipment.
2Use of energy by moving object
If high switching frequency is used to prevent excessive energy loss during switching transients, then power efficiency is improved, but EMI increases affecting wireless communication and electrical equipment
Solution Approach 1:
The periodic pause state reduces the overall switching activity, thereby lowering EMI while maintaining adequate power efficiency. The pause allows transient currents to settle, reducing the frequency of high-loss switching events without requiring continuously high switching frequencies.
Solution Approach 2:
The pause state maintains continuity of useful action by keeping the motor in a controlled state during the pause period, rather than completely shutting down. The motor continues to operate in a predictable manner during the pause, ensuring continuous and smooth operation while reducing switching-related EMI.
3Measurement precision
If conventional PWM control is used with DC-motors, then precise speed control is achieved, but complex calibration procedures are required when replacing motors due to inherent parameter differences
Solution Approach 1:
The controller performs self-calibration by automatically adapting to the new motor's characteristics during operation. The pause state and current monitoring enable the controller to learn the motor's parameters autonomously, eliminating the need for manual calibration procedures when motors are replaced.
Solution Approach 2:
The patent employs feedback mechanisms by continuously monitoring the motor current and using this information to adjust control parameters. The pause state provides opportunities for the controller to measure motor characteristics and adapt its control strategy, ensuring precise speed control without manual calibration.
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 solution effectively reduces EMI and power losses, enhances the stability of the drive arrangement, and simplifies the replacement process by eliminating the need for motor-specific calibration, making it more maintenance-friendly and cost-efficient.
Implementation Method 1
The drive arrangement comprises a DC-motor for driving the automatic door operator
Implementation Method 2
conventional drive arrangement with DC motors often utilize Pulse Width Modulation PWM
Data Source
AI summary
Method (100) for controlling a drive arrangement (200) for an automatic door operator (30) of an entrance system (10) having one or more movable door members (D1 . . . Dm), whereby the automatic door operator (30) is for causing movements of the one or more movable door members (D1 . . . Dm) between a closed position and an opened position, respectively. The drive arrangement (200) comprises a DC-motor (34) for driving the automatic door operator (30), a H-bridge (96) and a controller (32, 232) for controlling the drive arrangement (200). The H-bridge (96) comprises a first leg (A) and a second leg (B), the first leg (A) and second leg (B) both being connected to a first voltage supply line (97) and a second voltage supply line (98), the first voltage supply line (97) having a higher voltage than the second voltage supply line (98).