AC Load Voltage Control With Smooth PWM Phase Transition
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Solution Overview
Problem
Conventional systems with phase angle control using thyristors switch voltage abruptly, leading to noise and EMC emissions.
Innovation Solution
A method and device that provide a voltage to a load using pulse-width modulation starting from a first phase angle, transitioning smoothly to an unmodulated state at a second phase angle, with controlled derivatives to ensure a continually differentiable voltage curve, reducing noise and EMC emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If phase angle control using thyristors is used to switch voltage, then voltage can be switched on, but the voltage increases abruptly causing noise emissions and EMC emissions
Solution Approach 1:
The patent applies dynamics by transitioning from static abrupt switching to dynamic gradual voltage increase. The control device dynamically adjusts the voltage rise profile using a predetermined function that continuously changes the switching behavior, making the voltage increase smooth and continuous rather than abrupt, thereby reducing noise and EMC emissions while maintaining operational control.
Solution Approach 2:
The patent changes the parameter of voltage increase rate from constant (abrupt) to variable (smooth curve). By using a predetermined function with adjustable parameters, the system transforms the voltage switching characteristic from a step function to a continuous differentiable curve, reducing harmful emissions while preserving the ability to control voltage delivery to the load.
2Object-affected harmful factors
If voltage is switched on abruptly at the second phase angle, then voltage delivery is simple and direct, but noise emissions and EMC emissions increase
Solution Approach 1:
The patent introduces a control device as an intermediary between the AC voltage source and the load. This intermediary component implements the predetermined function to shape the voltage rise profile, acting as a mediator that transforms the abrupt voltage switching into a smooth transition, thereby reducing noise and EMC emissions while adding controlled complexity to the system.
Solution Approach 2:
The patent applies preliminary action by pre-defining the voltage rise profile using a predetermined function before actual voltage delivery. The control device prepares the voltage transition in advance by calculating and applying the appropriate switching pattern that ensures smooth voltage increase, preventing abrupt changes before they occur and thereby reducing harmful emissions.
3Object-affected harmful factors
If pulse-width modulation is used to control voltage with a smooth curve, then noise emissions are reduced, but the control system becomes more complex
Solution Approach 1:
The patent applies periodic action through pulse-width modulation (PWM) where the voltage is delivered in periodic pulses with varying widths. The control device modulates the pulse width according to a predetermined function, creating a smooth average voltage rise over time. This periodic switching approach reduces noise emissions compared to continuous abrupt switching while implementing controlled complexity through the modulation scheme.
Data Source
AI summary
In a method for providing a voltage for a load, e.g., for an inductor and/or coil of an electromagnetically actuable brake, e.g., of an electric motor, and device for carrying out the method, e.g., in a manner repeated over time, the positive half-wave of an, e.g., single-phase AC voltage is provided to the load in a pulse—with modulated manner starting from a first phase angle of the AC voltage, and in an unmodulated manner, e.g., and/or uncontrolled manner and/or directly, starting from a second phase angle.