Synchronous Motor Control for Dishwasher Noise Reduction
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Solution Overview
Problem
Synchronous electric motors in dishwasher machines experience cyclic hydraulic loads, leading to noise and substantial stresses due to pulse-type operation, which existing control systems fail to effectively mitigate.
Innovation Solution
A control system for synchronous electric motors that includes an electric position sensor, a rectifier circuit, a driver circuit with controlled electronic switches, and processing circuits to manage voltage and speed, reducing inrush current and noise by selectively controlling the stator winding voltage based on rotor position and speed requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the motor operates under cyclic hydraulic loads to meet washing pump requirements, then the motor can perform the washing function, but noise and vibrations increase substantially
Solution Approach 1:
The control system applies periodic voltage pulses to the stator winding synchronized with rotor position, creating controlled electromagnetic torque pulses that replace the uncontrolled mechanical pulse-type operation. This periodic electrical action smooths the torque delivery and reduces noise while maintaining washing pump functionality.
Solution Approach 2:
The system dynamically changes the voltage applied to the stator winding based on rotor position and speed requirements. By adjusting voltage parameters according to operational phase (startup, acceleration, steady-state), the motor achieves smooth torque characteristics that minimize noise and vibrations while maintaining required washing performance.
2Speed
If full voltage is applied during startup to achieve quick acceleration, then the motor starts faster, but inrush current and operational noise increase
Solution Approach 1:
The control system applies preliminary low-voltage excitation during the startup phase to gradually build up rotor speed and reduce inrush current. The voltage is increased in controlled steps as the rotor accelerates, achieving smooth startup without sudden current spikes or noise bursts.
Solution Approach 2:
The system dynamically adjusts the stator voltage based on real-time rotor position and speed feedback. During startup, voltage is modulated to provide optimal acceleration while limiting inrush current; during steady-state operation, voltage is adjusted to maintain required speed with minimal noise, creating a dynamic adaptation to operational 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
The control system reduces noise and vibrations by limiting the initial voltage during startup and adjusting voltage according to load requirements, allowing the motor to operate stably at required speeds without external speed measurement, thereby minimizing operational noise and stress.
Implementation Method 1
The sensor PS is disposed in a position in such a way that the signal H which it supplies at output has level switching, for example from low level to high level, when the rotor goes to a predetermined angular reference position
Implementation Method 2
a rectifier circuit RC, for example of the half-wave double-bridge type, with an input 2 which is designed to be connected to an alternating current power source, such as the mains supply at 50 or 60 Hz, in order to supply a predetermined direct current voltage VB as output
Implementation Method 3
This control circuit is connected to the output of the rectifier circuit RC, as well as to the stator winding W, and includes a plurality of controlled electronic switches SW1-SW4, such as, for example, transistors of the MOSFET type. The arrangement and control of the said switches SW1-SW4 are in such a way that they can permit passage of a current into the stator winding W selectively in one direction and in the opposite direction
Data Source
AI summary
The system (ECS) comprises a rectifier circuit (RC) to supply a direct current voltage (VB) as output; a driver circuit (DC) which is connected to a rectifier circuit (RC) and includes a plurality of controlled switches (SW1-SW4) which can permit passage of a current in the stator winding (W) selectively in one direction and in the opposite direction; a sensor (PS) which can supply a signal (H) which is indicative of the angular position of the rotor (R); and a control circuit (CC) which is designed to receive a signal (RS) which is indicative of the speed of rotation required (ωref) for the motor (M), and is connected to the position sensor (PS). The control circuit is designed to generate, from the passage of the rotor (R) to a predetermined position, a counting signal (N) which is a function of the time (t), and to reset this signal (N) when it reaches a predetermined value (Nref) corresponding to the speed of rotation required (ωref) for the motor (M); and then to control the driver circuit (DC) selectively on the basis of the position signal (H) of the rotor or on the basis of the counting signal (N), when the speed of rotation (Δ) of the motor (M) is respectively lesser and greater than the speed required (Δref).