Electricity: motor control systems – Closed loop speed control system for dc motor with commutator – Armature control by digital or combined analog and digital...
Reexamination Certificate
2000-07-10
2002-09-03
Dang, Khanh (Department: 2837)
Electricity: motor control systems
Closed loop speed control system for dc motor with commutator
Armature control by digital or combined analog and digital...
C388S906000, C388S907500, C318S245000, C318S438000
Reexamination Certificate
active
06445879
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus and method for braking a washing machine. More particularly, this invention relates to an apparatus and a method for braking a washing machine without using a capacity dynamic braking resistor.
2. Description of the Prior Art
Referring to
FIG. 1
, the conventional braking system for a washing machine comprises: a rectifier
101
converting the AC power of the system to the DC voltage; a capacitor filter
102
smoothing the rectified DC voltage; a motor driver
103
driving the motor by using the smoothed DC voltage; a voltage detector
104
detecting the voltage of the system when the motor M is suddenly braked; a voltage comparator
105
comparing the detected voltage of the voltage detector
104
and the reference voltage which is previously specified in the system; a switch element
106
determining the on/off functions of the dynamic brake resistor R
1
according to the comparison result of the voltage comparator
105
; a sensor
107
detecting a revolution position and the rotating speed of the motor M; a microcomputer
108
controlling the motor operation by using the sensor
107
output signal and the overall logic in relation to the over-flown voltage in the system; and a signal output device
109
generating a control signal in accordance with the control of the microcomputer
108
.
The dynamic braking resistor R
1
discharges the revival voltage into thermal energy to protect the system when the inertia energy of the motor or the load converts to electric energy resulting in increase of the revival voltage charged in the capacitor filter
102
.
Referring to
FIG. 1
, the overall operation of the conventional braking system for a washing machine is described hereinafter.
Firstly, the commercial AC power supplied from the outside power source is converted by the rectifier
101
into the DC voltage which is then smoothed by the capacitor filter
102
before being supplied to the motor driver
103
.
A washing machine is operated as the motor driver
103
converts the DC voltage smoothed by the capacitor filter
102
to drive the motor M.
However, in the event that a lid of a washing machine is opened during the dehydration operation or an unbalance state of the tub is detected, the rapidly rotating motor M must be braked to make a sudden stop of the tub.
The motor M is a brushless DC motor and the current flows in a discharged direction from the capacitor filter
102
to the motor M as the motor M becomes the load during the normal washing operation.
However, if the motor M is suddenly braked while it's in the rapidly rotating state, the motor M becomes a power generator and then a direction of flow of the current changes to the charged direction which is from the motor M to the capacitor filter
102
due to the induction electromotive power generated from the motor M.
At this point, if the revival voltage charged in the capacitor filter
102
is not discharged, the voltage level increases to a level exceeding the inner voltage of the designed circuit damaging the peripheral circuit and devices.
Therefore, the conventional system is equipped with the voltage detector
104
, the voltage comparator
105
and the dynamic braking resistor R
1
in order to discharge the over-flown voltage in the system resulted from braking of the motor.
In event that the motor M is braked during the washing or dehydration process, the voltage detector
104
measures the voltage between the capacitor filter
102
and the motor M, and the measured voltage is delivered to the voltage comparator
105
.
Thereafter, the voltage comparator
105
compares the voltage between the reference voltage Vref and the detected voltage Vdc measured by the voltage detector
104
. And the result of comparison is then outputted to the switching element
106
, where the on/off control functions are performed. If the detected voltage Vdc exceeds the reference voltage Vref, the braking resistor R
1
is activated as the switching element
106
turns to on state.
As a result, the over-flown voltage generated between the capacitor filter
102
and the motor M does not flow to the capacitor filter
102
, but instead to the dynamic braking resistor R
1
thereby the system is maintained at the regular voltage-level as the over-flown voltage is discharged into thermal energy.
When the detected voltage Vdc between the capacitor filter
102
and the motor M is lower than the reference voltage Vref, the braking resistor R
1
is turned to off state by the switching element
106
. The motor M is then braked as the current is flowing only to the capacitor filter
102
and not to the dynamic braking resistor.
In the event that the motor M is decelerated quickly or the load inertia of the motor M becomes massive, the revival energy generated by the motor M becomes much greater, and the revival energy is revived to the motor driver
103
, causing a rise in the voltage that are being charged to the capacitor filter
102
. If the DC voltage rise over 380V, the dynamic braking resistor R
1
is activated to discharge the revival energy into thermal energy.
One of the disadvantages of the conventional method is that the size and the capacity of the dynamic braking resistor R
1
installed on the outer part of the system is large making the system more complicated, thus increase the production cost of the system.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide an apparatus and method for braking a washing machine without using the dynamic braking resistor.
It is another object of this invention to provide an apparatus and method for braking a washing machine for effectively processing the over-flown voltage in the system due to the motor braking result of the interruption of electric power or in the event of emergency motor braking.
It is a still another object of this invention to provide an apparatus and method for braking a washing machine for smoothly operating the braking of a washing machine by setting up a plurality of braking modes in which each mode has a different barking capability, and the braking mode is selected based on the rotating speed of the motor.
These and other objects are satisfied an apparatus for braking a washing machine comprising: a rectifier for converting the AC power of the system to the DC voltage; a capacitor filter for smoothing a rectified DC voltage; a motor driver for driving the motor by converting a smoothed DC voltage to a three-phase voltage and frequency; a voltage detector for detecting the smoothed DC voltage in real-time; a sensor detecting for a position and a speed the motor in real-time; and a microcomputer for outputting a control signal based on a comparison between an output signal of a sensor and a predetermined reference voltage to activate charge /discharge operations of the voltage between a capacitor filter and a motor.
Other objects of the invention are satisfied by the apparatus for braking a washing machine comprising: a converter for converting the power supplied from the outer power source into a voltage necessary for the system, and performing switching operation according to the control signal; a capacitor filter for stably smoothing the converted voltage by said converter; a motor driver for generating the voltage in order to drive the motor through the voltage inputted from the capacitor filter; a voltage detector placed in between the motor driver and the capacitor filter for detecting the voltage flowing in the system; a sensor for detecting a motor position and speed; and a microcomputer for outputting a control signal to control the converter and the motor driver based signals inputted from the voltage detector and the sensor.
Other objects of the present invention are satisfied by a method for braking a washing machine comprising the steps of: setting up an initial data of a duty ratio corresponding to a detected speed and a rotating position; discharging a voltage of the capacitor filter during a duty-on cycle according to the duty ra
Ko Beom Seok
Lee Chul Woong
Lee Joo Hwan
Ra In Hwan
Youn Sang Chul
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