Synchronous Motor Control via Back-EMF Detection and Triac Switching

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Solution Overview

Problem

Existing control systems for synchronous electric motors are complex and costly, and they fail to efficiently manage steady-state rotation and adapt to changes in load and supply voltage, leading to inefficiencies and potential operational instability.

Innovation Solution

A control system comprising a microcontroller, triac, and detector circuits that regulate the conduction of the triac based on the polarity and magnitude of the back-EMF and supply voltage, optimizing the duration of zero-current intervals to reduce losses and maintain efficiency across varying loads and voltages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If existing control systems are used for synchronous electric motors, then the motor can operate, but the control system is complex and costly to manufacture

Engineering Contradiction:

Improvemanufacturing costVSAvoidcontrol system complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent extracts the essential control function from complex existing systems by using only a simple triac switch controlled by a microcontroller to regulate motor operation during steady-state rotation, eliminating the need for complex sensor systems and sophisticated control circuits while maintaining effective load and voltage adaptation

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The control system utilizes the motor's own back-EMF signal as the sensing input for the microcontroller, allowing the system to self-regulate based on its own operating conditions without requiring external sensors or complex feedback mechanisms, thereby simplifying the control architecture

Inventive Principle:

Principle #25Self-service

2Adaptability or versatility

If existing control systems are used, then the motor can operate, but they fail to efficiently manage steady-state rotation and adapt to changes in load and supply voltage

Engineering Contradiction:

Improveadaptation to load and voltage changesVSAvoidcopper losses

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The microcontroller continuously monitors the motor's back-EMF signal and uses this feedback to detect changes in load and supply voltage conditions, automatically adjusting the triac conduction angle to optimize motor performance and minimize copper losses under varying operating conditions

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The control system dynamically adjusts the triac switching characteristics based on real-time detection of load and voltage changes, enabling the motor to adapt its operation during steady-state rotation to maintain efficiency across different operating points

Inventive Principle:

Principle #15Dynamics

3Reliability

If existing control systems are used, then the motor can operate, but they lead to inefficiencies and potential operational instability

Engineering Contradiction:

Improveoperational stabilityVSAvoidefficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent replaces complex mechanical and electronic control mechanisms with a simplified microcontroller-based system that uses software logic to manage motor operation, improving both reliability through fewer moving parts and efficiency through precise digital control of the triac switching

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 system achieves high efficiency and stability by reducing copper losses, ensuring positive torque, and adapting to changes in load and voltage, while maintaining constant power consumption and minimizing waveform imbalances.

Implementation Method 1

an electronic switch which in the example illustrated is a triac TR connected in series to winding W of motor M between two terminals A and B intended to be connected to an alternating current supply voltage source V

Methodology Applied

Scientific EffectTriac conduction: Conduction (electrical)

Implementation Method 2

under particular operating conditions the voltage at the ends of stator winding W of motor M is represented by the magnitude of the back-electromotive force (back-EMF) developed on this winding

Methodology Applied

Scientific EffectBack-electromotive force: Electromagnetic Induction

Implementation Method 3

a first detector circuit indicated by 1. This circuit is a voltage detector and has its input connected to the ends of the winding of stator W and its output connected to microcontroller MC

Methodology Applied

Scientific EffectVoltage detection: Electric Field

Data Source

PatentUS8183805B2System for controlling the steady-state rotation of a synchronous electric motor

Publication Date: 2012.05.22 ASKOLL P&C

AI summary

The control system comprises a switch (TR) in series with a stator winding (W) between two terminals (A, B) connected to an alternating supply voltage source (V), a first detector circuit (2) capable of providing a signal (Voi) indicating when the current (I) in that winding (W) is zero, a second detector circuit (1) capable of providing a signal (Vw) indicating the magnitude of the supply voltage (V), and a control unit (MC) connected to the first and second detection circuits (2; 1) and designed to control the switch (TR) in such a way as to cause an alternating current (I) of the same frequency as the supply voltage (V) and having alternating positive and negative phases (11, 12) to pass through the winding (W), separated by intervals during which it remains at zero, of a duration (tp) which varies according to an increasing function of the magnitude of the supply voltage (V).