Washing Machine Motor Braking to a Reduced Non-Zero Speed
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Solution Overview
Problem
Conventional washing machines face challenges in efficiently braking the spin basket from operational speeds to reduced non-zero speeds due to high costs and reduced motor life associated with existing braking methods, particularly dynamic and regenerative braking systems, and DC injection braking, which results in excessive current spikes and thermal stresses.
Innovation Solution
The method involves collapsing the motor's rotating magnetic fields for a predefined time and then applying DC braking voltage at a controlled ramp rate to achieve a controlled braking torque, followed by a soft start to maintain the reduced speed, utilizing a motor control circuit to manage the process for synchronous or asynchronous motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If dynamic or regenerative braking methods are used, then braking torque is generated, but component cost and circuit complexity increase
Solution Approach 1:
The patent replaces complex mechanical braking systems and sophisticated electronic braking circuits with a simplified DC injection braking method. By applying DC voltage to the stator windings, a stationary magnetic field is created that interacts with the rotating rotor to produce braking torque, eliminating the need for complex dynamic braking circuits with resistors and synchronization hardware.
Solution Approach 2:
The patent changes the electrical parameters applied to the motor windings from AC (rotating magnetic field) to DC (stationary magnetic field) during the braking phase. This parameter change allows the creation of a stationary magnetic field that provides effective braking torque while simplifying the control circuitry, as DC injection requires only basic voltage switching rather than complex frequency and phase control.
2Force
If DC injection braking is applied at high loads and speeds, then braking is achieved, but current spikes and thermal stresses increase
Solution Approach 1:
The patent applies preliminary action by first reducing the motor speed to a lower range before applying DC injection braking. This preliminary speed reduction prevents the excessive current spikes and thermal stresses that would occur if DC braking were applied directly at high speeds and loads, while still achieving effective braking when needed.
Solution Approach 2:
The patent provides beforehand cushioning by implementing speed reduction as a protective measure before DC braking engagement. This cushioning approach mitigates the harmful thermal stresses and current spikes by ensuring the motor operates in a safer operating range when DC braking is applied, extending motor life while maintaining braking effectiveness.
3Speed
If mechanical braking systems are used, then braking to zero speed is achieved, but maintenance costs and component wear increase
Solution Approach 1:
The patent replaces mechanical braking systems with DC injection braking, eliminating brake pads, shoes, and associated mechanical components that require maintenance. The electrical braking method uses the motor's own electromagnetic fields to provide braking force, removing wear-prone mechanical parts and reducing maintenance requirements while achieving effective braking to zero speed.
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
This approach reduces the cost and wear on components while preventing excessive current spikes, allowing for efficient and controlled braking to avoid vibrations and noise, and extending the motor's life by distributing the braking load effectively across multiple windings.
Implementation Method 1
DC injection braking is a method for braking synchronous or asynchronous motors wherein DC voltage is applied to the stator windings to produce a stationary magnetic field. The spinning rotor is magnetically drawn to this stationary magnetic field, which acts as a drag (i.e., a braking force) on the rotor
Data Source
AI summary
A method of braking a washing machine from an operational speed to a reduced non-zero speed is provided (as well as a washing machine incorporating the method) for a washing machine driven by one of a synchronous or asynchronous motor. Upon receipt of a speed reduction signal, the motor rotating magnetic fields are collapsed for a defined time period. After the defined time period, DC braking voltage is applied to the motor stator windings at a controlled ramp-up rate to an amplitude to generate a controlled ramped braking torque on the motor until the motor has slowed to a defined reduced speed. Thereafter, the amplitude of the DC braking voltage is set to 0V and the motor is soft started to an amplitude and reduced frequency needed to maintain the defined reduced speed.