METHOD TO BRING A WASHING MACHINE MOTOR INTO AN INTRINSICALLY SAFE STATE
Publication Date: 2014-Nov-20
The IP.com Prior Art Database
The described method and apparatus utilizes a seamless transition between hardware and software to place a motor in an intrinsically safe state. The hardware enables a power stage and shorts motor phases together to create a safe state. The software when initialized takes control of the safe state until the motor is completely stopped. This algorithm provides "passive braking" of a PMSM or BLDC motor by turning on all low-side IGBT's and simultaneously turning off all high-side IGBTs.
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This disclosure relates generally to motors utilized in many different applications. As one particular example, the following will be described with reference to appliances, and more particularly to the motor of a washing machine.
Braking systems are often used in washing machines to stop the rotation of the motor and washing drum when it is unsafe for the motor or drum to rotate. Unsafe conditions may be present when the machine is first turned on, the door is opened, or the machine is working incorrectly. In applications other than a washing machine, stopping the rotation of the motor may be very important to ensuring safe use of the equipment. While other braking systems utilized may prevent unsafe conditions and injury to the user, they may also damage hardware within the appliance.
Previous attempts to safely stop motor or washing drum rotation without damaging the equipment have included the use of power resistors and direct current ("DC") braking. While power resistors may protect the inverter DC bus from charging during a fault or during braking conditions, such DC braking is very noisy on a permanent magnet synchronous motor ("PMSM") or brushless DC motor ("BLDC"), due to the interaction with the rotor magnets.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an exemplary configuration of an inverter power stage in accordance with the present invention.
Figure 2 is an exemplary configuration of an inverter and motor in accordance with the present invention.
This disclosure discusses the desirable pairing of hardware and software together to quietly, safely, and efficiently stop a motor without damaging hardware and without creating unsafe conditions for the user.
METHOD TO BRING A WASHING MACHINE MOTOR
INTO AN INTRINSICALLY SAFE STATE
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The apparatus and/or method comprising of pairing hardware and software to stop a motor may be utilized with motors utilized in many different applications. As one particular example, the following description will reference appliance motors, and more particularly the motor(s) (typically, but not limited to PMSM and/or BLDC) of a washing machine.
At startup before the software is initialized, the hardware enables the power stage, which, in some embodiments, comprises insulated-gate bipolar transistors ("IGBTs"). After enabling the power stage, the hardware shorts the three motor phases together. When the software is initialized, it takes control and continues this safe state until the motor is completely s...