Dynamic Triac Firing for Commutator Motor Phase Control
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Solution Overview
Problem
Existing phase control methods for electric motors with commutators suffer from phase shift-dependent power control issues, leading to noise, increased electromagnetic compatibility (EMC) emissions, reduced brush service life, and heat loss due to inefficient triac firing times based on maximum phase shifts, resulting in suboptimal operation.
Innovation Solution
A control device that taps the voltage potential between the triac and the electric motor to detect zero crossings of the motor current, using voltage jumps to determine optimal triac firing times, ensuring the triac is triggered only when the motor current exceeds the holding current, thereby reducing harmonic generation and power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the triac is triggered after a defined minimum time based on maximum phase shift to ensure sufficient motor current, then the triac firing reliability is improved, but the harmonic generation increases and brush service life decreases
Solution Approach 1:
The patent applies dynamics by making the triac triggering time variable rather than fixed. The control device dynamically adjusts the triggering time based on the actual phase shift detected in each operating state. When the phase shift is small, the triac is triggered earlier; when the phase shift is large, the triac is triggered later. This dynamic adjustment ensures the triac always fires when motor current exceeds the holding current, eliminating harmonics while maintaining firing reliability.
2Reliability
If the triac is triggered after a defined minimum time based on maximum phase shift to ensure sufficient motor current, then the triac firing reliability is improved, but the brush service life decreases
Solution Approach 1:
The patent applies dynamics by making the triac triggering time variable rather than fixed. The control device dynamically adjusts the triggering time based on the actual phase shift detected in each operating state. When the phase shift is small, the triac is triggered earlier; when the phase shift is large, the triac is triggered later. This dynamic adjustment ensures the triac always fires when motor current exceeds the holding current, eliminating harmonics while maintaining firing reliability.
3Reliability
If the triac is triggered after a defined minimum time based on maximum phase shift to ensure sufficient motor current, then the triac firing reliability is improved, but the motor self-heating increases
Solution Approach 1:
The patent applies dynamics by making the triac triggering time variable rather than fixed. The control device dynamically adjusts the triggering time based on the actual phase shift detected in each operating state. When the phase shift is small, the triac is triggered earlier; when the phase shift is large, the triac is triggered later. This dynamic adjustment ensures the triac always fires when motor current exceeds the holding current, eliminating harmonics while maintaining firing reliability.
4Reliability
If the triac is triggered after a defined minimum time based on maximum phase shift to ensure sufficient motor current, then the triac firing reliability is improved, but the power loss increases
Solution Approach 1:
The patent applies dynamics by making the triac triggering time variable rather than fixed. The control device dynamically adjusts the triggering time based on the actual phase shift detected in each operating state. When the phase shift is small, the triac is triggered earlier; when the phase shift is large, the triac is triggered later. This dynamic adjustment ensures the triac always fires when motor current exceeds the holding current, eliminating harmonics while maintaining firing reliability.
Data Source
Figure 1~2
AI summary
The invention relates to a method for operating an electric motor (2) having a phase angle control with the following steps: Applying an AC voltage to a series connection of the electric motor (2) and a switching element (4), particularly a triac, wherein the switching element (4) connects through by applying an ignition signal and suppresses the flow of a current if the amount of current falls below a holding current; determining the time of a zero crossing of a virtual motor current that would flow if the switching element (4) were connected through; and turning on the switching element (4) at an activation time that is dependant on the time of the zero crossing of the virtual motor current.