AU2006202342B2 - Method of controlling motor-driven washing machine and control system for the same - Google Patents

Description

P/00/01 I Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT (ORIGINAL) Name of Applicant: LG Electronics Inc., of 20, Yoido-dong, Youngdungpo-gu, Seoul 150-721, SOUTH KOREA Actual Inventors: KOO, Bon Kwon HONG, Kwon Ki LYU, Jae Cheol LEE, Woon Yong BANG, Jong Chul CHO, In Haeng OH, Min Jin SON, Kweon KIM, Jong Ho Address for Service: DAVIES COLLISON CAVE, Patent & Trademark Attorneys, of 1 Nicholson Street, Melbourne 3000, Victoria, Australia Ph: 03 9254 2777 Fax: 03 9254 2770 Attorney Code: DM Invention Title: Method of controlling motor-driven washing machine and control system for the same The following statement is a full description of this invention, including the best method of performing it known to us:- P p cp2003230345di I spe doc-35I6 METHOD OF CONTROLLING MOTOR-DRIVEN WASHING MACHINE AND CONTROL SYSTEM FOR THE SAME BACKGROUND OF THE INVENTION 5 Field of the Invention The present invention relates to a washing machine, and more particularly, to a method of controlling a motor-driven washing machine and a control system for the same. 10 Discussion of the Related Art Motor-driven automatic washing machines are common these days. A typical washing machine may include a motor for driving an agitator and a rotatable tub serving both as a wash tub and a dehydration tub and the motor is coupled to a drive shaft. During a typical wash or rinse cycle, the motor is caused to rotate back and forth to agitate the 15 clothes and water in the wash tub for cleaning or rinsing of the clothes. In addition, during a spin cycle, the motor spins the wash tub containing a load of wet clothes to be dehydrated to remove water from the wet clothes by centrifugal force. Because the wash tub rotates at a very high speed, many problems can occur. For example, if the operation of the motor is not stopped properly when a user mistakenly 20 opens a washer door and sticks a hand into inside of the tub, the user may be seriously harmed. The user should be advised of such error promptly so that the error of the motor or any other components that associates with the motor can be quickly fixed. In another example, when a control for braking a motor in motion during a spin cycle is not properly done, the motor-clutch mechanism may generate a noise and the 25 mechanism can be damaged due to the motion of the heavy wash tub at a high speed. SUMMARY OF THE INVENTION Accordingly, the present invention is directed to a method of controlling a motor driven washing machine and a control system for the same that substantially obviate one or 30 more problems due to limitations and disadvantages of the related art. According to the present invention there is provided a method of controlling a P \oprgcp\203230345dhy I spedoc-31/05/06 -2 motor-driven washing machine, the method comprising the steps of: initiating a wash cycle by operating a motor provided in the washing machine according to a washing option selected by a user; generating a motor-brake signal to brake the operation of the motor when a motor 5 interruption command is generated and measuring a brake period which represents a total length of time it takes to completely stop the operation of the motor; determining malfunction of the motor based on whether the measured brake period exceeds a predetermined period of time; and displaying a warning message on a display unit, the message indicating the 10 determined malfunction of the motor. The invention also provides a control system for a washing machine, the control system comprising: a motor rotating a washing tub or an agitator provided in the washing machine according to a washing option selected by a user; 15 a microprocessor operatively coupled to the motor for braking operation of the motor when a motor-interruption command is generated and measuring a brake period which represents a total length of time it takes to completely stop the operation of the motor, the microprocessor determining malfunction of the motor based on whether the measured brake period exceeds a predetermined period of time; and 20 a display unit displaying a warning message indicating the determined malfunction of the motor upon receiving a control signal from the microprocessor. It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 25 BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the 30 principle of the invention. In the drawings: FIG. IA illustrates a control system that drives a motor provided in a washer; P:\peri \2003230345dav I p doc-3 5eD6 -3 FIG. lB illustrates the detailed structures of the motor brake unit 60, the transformer 50 and the motor 81 shown in FIG. I A; FIG. I C illustrates a current flow (Li) of the motor brake unit 60 when the phase shifted voltage applied to the motor brake unit 60 is less than Vc; 5 FIG. ID illustrates a method of controlling a motor provided in a washer; FIG. 2A illustrates an apparatus of controlling load units (e.g., a motor) in a washer; FIG. 2B illustrates a method of controlling load units in a washer; FIG. 3A illustrates an apparatus of detecting malfunction of a motor in a washer 10 according to an embodiment of the present invention; FIG. 3B illustrates a method of detecting malfunction of a motor in a washer according to the embodiment of the present invention; FIG. 4A and FIG. 4B illustrate a method of interrupting (braking) operation of a motor in a washer; 15 FIG. 5A illustrates a control system that drives a motor provided in a washer; FIG. 5B illustrates a method of controlling a motor in a washer; FIG. 6A illustrates a control system that drives a motor provided in a washer; FIG. 6B illustrates a method of controlling a motor in a washer; FIG. 7A illustrates a control system controlling a motor in a washer; 20 FIG. 7B illustrates a method of controlling a motor in a washer; FIG. 8A illustrates an apparatus of controlling operation of a motor in a washer; FIG. 8B illustrates a method of controlling operation of a motor in a washer; FIG. 9A illustrates a control system that drives a motor provided in a washer; FIG. 9B illustrates a method of controlling a motor in a washer; and 25 FIG. 10 illustrates a circuitry for limiting a motor current in an electrical appliance. DETAILED DESCRIPTION OF THE INVENTION Reference will now be made in detail to a preferred embodiment of the present invention, an example of which is illustrated in Figures 3A and 3B of the accompanying 30 drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts of embodiments of other systems and methods PeopeAgp 03230456v I spe doc-3 M506 -4 for controlling washing machines. Embodiment (1) FIG. IA illustrates a control system that drives a motor provided in a washer 5 according to an embodiment of the present invention. Referring to FIG. 1A, the control system includes a power supply unit 40 rectifying and/or smoothing an AC power voltage generated by a power source, a transformer 50 having a converter (not illustrated) and for converting the rectified AC voltage into a DC voltage and a capacitor (not illustrated) for storing the converted DC voltage, a motor 81 rotating a tub and/or an agitator provided in 10 the washer, a motor brake unit 60 braking the operation of the motor 81 by applying an input voltage to the motor 81 upon receiving a brake control signal, and a controller 70 measuring the DC voltage stored by the transformer 50 and generating the brake control signal to the motor brake unit 60. The DC voltage stored in the capacitor of the transformer 50 is used for driving the 15 motor 81, and the motor 81 transmits the dynamic energy to a clutch (not illustrated) that engages with the tub and/or agitator provided in the washer for washing a load of clothes to be washed. When a user inputs a command for interrupting (braking) the motor operation by turning the power of the washer off, opening a washer door, or manually touching a key control panel, the controller 70 generates a motor interruption signal to the 20 motor brake unit 60. In addition, the controller 70 continuously monitors the speed of the motor 81 and outputs the motor speed information to the transformer 50, which then applies a voltage corresponding to the motor speed to the motor brake unit 60. The motor brake unit 60 shifts the phase of the voltage outputted by the transformer 50 by 180 degrees and applies the phase-shifted voltage (phase-reversed voltage) to the 25 motor 81 so as to brake the motor operation. However, when a phase-shifted voltage corresponding to a speed value higher than a certain motor speed is applied to the motor 81, a noise may be generated in the motor-clutch mechanism and the mechanism may be damaged. This is because the actual rotational displacement of the clutch is greater than the rotational displacement of the motor 81 due to the rotational speed difference between 30 the motor 81 and the clutch. For this reason, the controller 70 initially stores a critical phase-shift voltage Vc that starts to generate the noise in the motor-clutch mechanism and P e\gcp\2003230345div I spe doc.35 6 -5 that may damage the mechanism, and it performs a motor brake by shorting the power input terminals of the motor 81 if the current phase-reversed voltage is greater than Vc. FIG. IB illustrates the detailed structures of the motor brake unit 60, the transformer 50 and the motor 81 shown in FIG. IA. As shown in FIG. IB, the motor brake 5 unit 60 comprises three pairs of insulated gate bipolar transistors (hereinafter "transistor") connected in parallel, where each pair comprises two transistors connected in series. A diode (Dl to D6) is connected to each transistor, which can be shorted by the diode. Transistors T2, T4 and T6, which are directly connected to three winded wires of the motor 81, apply the voltage supplied by the transformer to the winded wires of the motor 81, 10 respectively, for operating or braking the motor 81. FIG. IC illustrates a current flow (LI) of the motor brake unit 60 when the phase shifted voltage applied to the motor brake unit 60 is less than Vc. On the other hand, a current flow (L2) of the motor brake unit 60 when the phase-shifted voltage is greater than or equal to Vc. In other words, if the controller 70 determines that the voltage being 15 inputted to motor brake unit 60 is greater than or equal to Vc, the motor brake unit 60 shorts the input terminals of the motor 81 as shown in FIG. lB for a predetermined period of time (e.g. 0.5 see). As shown in FIG. 1B, the connections between the transformer 50 and the motor 81 are shorted by activating T2, T4 and T6 and D2, D4 and D6 and by deactivating TI, T3 and T5. Therefore, the voltage of the transformer 50 is not applied, 20 but instead, the voltage previously applied to the winded wires 85 of the motor 81 are consumed for braking the motor operation. After the input terminals of the motor 81 are shorted for 0.5 sec, the speed of the motor 81 is reduced and the reduced motor speed is transmitted to the controller 70, which then applies a voltage corresponding to the reduced motor speed to the motor driving unit 60 so that the motor 81 can be stopped without 25 generating any noise in the motor-clutch mechanism. Reference will now be made in detail to a method of controlling a motor provided in a washer according to the first embodiment of the present invention, which is illustrated in FIG. ID. Initially, a user inputs a command for interrupting (braking) the motor operation by turning the power of the washer off, opening a washer door, or manually 30 touching a key input panel (SSI). Next, the controller 70 controls the transformer 50 to apply a voltage corresponding to the current motor speed to the motor brake unit 60, which P:\opap\2003230345div Isp.doM-3 5/06 -6 then performs a motor brake by shifting the phase of the voltage by 180 degrees and applying the phase-shifted voltage (phase-reversed voltage) to the motor 81 (S2). Thereafter, the controller 70 measures the current speed of the motor 81 again and compares the voltage corresponding to the measured motor speed with a critical phase 5 shift voltage Vc (S3), which is previously stored by the controller and represents a value of the phase-shifted voltage that causes the motor-clutch mechanism to generate a noise if applied to the motor 81. If the voltage corresponding to the current motor speed is less than Vc, steps S2 and S3 are repeated again. On the other hand, if the voltage is greater than or equal to Vc, 10 the controller 70 performs a motor brake by shoring the power input terminals of the motor 81 for a predetermined period of time T (e.g. 0.5 sec) so that the voltage corresponding to the current motor speed is not applied to the motor 81. Next, if the controller 70 determines that the operation of the motor 81 is stopped (S5), it terminates the motor brake algorithm. Otherwise, steps SI to S5 are repeated until the motor operation is stopped. 15 Embodiment (2) -7 FIG. 2A illustrates an apparatus of controlling load units (e.g., a motor) in a washer according to a second embodiment of the present invention. Refering to FIG. 2A, the apparatus includes a key input unit 210 receiving commands from a user for a wash cycle, a door sensor 240 for sensing opening of a washer door of the washer, and a load controller 5 230 that executes an interrupt program or algorithm for interrupting operations of load units 260 upon receiving a signal indicating the opening of the washer door, where the load units 260 include a motor rotating a tub and/or an agitator provided in the washer, a water supply system supplying water to the tub, and a drain system draining water from the tub. The apparatus shown in FIG. 2A further includes a main controller 220 that generates 10 control signals to initiate the wash cycle according to the user's commands and controls the operations of the load units based upon whether the interrupt program is properly executed by the load controller 230. The apparatus further includes a memory 250 (e.g., EEPROM) for storing a plurality of parameter values that correspond to various washing options and a display unit 270, such as an LCD display, that displays information 15 indicating the opening of the washer door upon receiving a control signal from the main controller 220. When a user inputs commands for a wash cycle through the key input unit 210, the main controller 220 transmits the commands to the load controller 230. Then the load controller 230 performs a wash cycle by driving the load units 260 according to the 20 received commands. The load units 260 include a motor rotating a tub, and it may further include a water supply supplying water to the tub and a drain draining water from the tub. When the door sensor 240 detects or senses opening of a washer door, it sends a signal indicating the opening of the washer door to the load controller 230 and the main controller 220. Thereafter, the load controller 230 runs an interrupt program (e.g., 25 executing an interrupt algorithm) for interrupting or suspending operations of the load -8 units 260. The main controller 220 detennines whether the load controller 230 has executed the interrupt program properly. If the main controller 220 determines that the load controller 230 has not executed the program properly, it generates a direct control signal to the load units 260 for properly interrupting or suspending the operations of the 5 load units 260. For example, the load controller 230 periodically transmits speed (RPM) information of a motor which is operatively coupled to the load controller 30 so that the main controller 220 can determine whether the load controller 230 has executed the interrupt program properly by monitoring the speed information of the motor. Reference will now be made in detail to a method of controlling load units in a 10 washer according to the second embodiment of the present invention, which is illustrated in FIG. 2B. Referring to FIG. 2B, the main controller 220 initially generates control signals to initiate a wash cycle according to a washing option selected by a user (S21 1). If the main controller 220 detects opening of a washer door during the wash cycle (S212), it determines whether the load controller 230 has executed an interruption program (e.g., an 15 interrupt algorithm) properly by receiving operation data of the load units 260 from the load controller 230 via a data communication, line, such as a serial communication line, and by monitoring the received operation data (S213). If it is determined in step S213 that an interruption program is properly executed by the load controller 230, then the main controller 220 allows the load controller to interrupt the operations of the load units 260 20 (S214). On the other hand, if the interrupt program is not properly executed, the main controller 220 sends direct control signals to the load units 260 for interrupting the operations of the load units 260 (S215). One of the advantages of controlling the load units of a washer according to the second embodiment described above is that a reliable control for interrupting operations of the load units is still achieved even when any error occurs in 25 interrupting the operations of the load units by the load units.

-9 Embodiment (3) FIG. 3A illustrates an apparatus of detecting malfunction of a motor in a washer according to a third embodiment of the present invention. Referring to FIG. 3A, the 5 apparatus includes a key input unit 310 receiving commands from a user for a wash cycle, a motor 340 rotating a tub and/or an agitator in the washer, a speed measuring unit 330 measuring the speed of the motor 340, and a counter 320 that measures interruption periods of the motor 340. An interruption period of the motor 340 represents a period of time that it takes for the motor 340 to completely stop since an interruption command is 10 inputted by the user through the key input unit 310 or opening of a washer door (not illustrated) of the washer is detected. The apparatus shown in FIG. 3A further includes a memory 370 (e.g., EEPROM) that stores the measured interruption period of the motor 340 if the measured period is greater than a predetermined length of time, a microprocessor 360 that determines malfunction of the motor 340 based upon whether a total number of 15 the stored interruption periods, which are greater than the predetermined length of time, is greater than a threshold frequency, and a display unit 350 (e.g., an LCD) that indicates the malfunction of the motor 340 upon receiving a control signal from the microprocessor 360. When the microprocessor 360 receives an interruption command from the user through the key input unit 310 or detects opening of a washer door of the washer, it 20 generates an interruption signal to the motor 340 to interrupt or stop operation of the motor 340. Thereafter, the counter 320 measures an interruption period of the motor 340, which represents a period of time it takes for the motor 340 to completely stop since the interruption signal is generated by the microprocessor 360, and the microprocessor stores the measured interruption period in the memory 370 if the measured period is greater than 25 a predetermined length of time. Next, the microprocessor 360 determines whether a total - 10 number of the interruption periods stored in the memory 370 is greater than a threshold frequency. If the total number of periods is determined to be the threshold frequency, the microprocessor 360 sends a control signal to the display unit 350 to display a message indicating malfunction of the motor 340 to the user. 5 Reference will now be made in detail to a method of detecting malfunction of a motor in a washer according to the third embodiment of the present invention, which is illustrated in FIG. 3B. Refeming to FIG. 3B, when power is supplied to a washer (S31) and the microprocessor 360 determines that a command for initiating a wash cycle is received from the user through the key input unit 310 (S32), the microprocessor 360 initiates the 10 wash cycle according to a wash option selected by the user (S33). Thereafter, when the microprocessor 360 determines that an interruption command is received from the user through the key input unit 310 or opening of a washer door of the washer is detected (S34), it generates an interruption signal to interrupt or stop operation of the motor 340 and measures an interruption period of the motor 340 using the counter 320 (S36). The 15 interruption period of the motor 340 represents a period of time it takes to completely stop the operation of the motor 360 since the interruption signal is generated. On the other hand, if it is determined in step S34 that no interruption command is received from the user and the opening of the washer door is not detected, the microprocessor 360 continues the wash cycle (S35). 20 Referring back to FIG. 3B, after the interruption period of the motor 340 is measured in step S36, the microprocessor 360 determines whether the measured interruption period is greater than a predetermined length of time Tpredetermined (S37). If it is, it stores the measured interruption period in the memory 370 (S38), and otherwise, it finishes interrupting the operation of the motor 340 (S41). Next, the microprocessor 360 25 further determines whether a total number of the interruption periods, which are stored in - 11 the memory 370 up to the present time, is greater than a threshold frequency value Npredecermined (S39). If the total number of periods is determined to be greater than the threshold frequency value in step S39, the microprocessor 360 sends a display control signal to the display unit 350 to display a message indicating malfunction of the motor 340 5 to the user (S40). Using the apparatus and method according to the third embodiment of the present invention, a user can easily and conveniently be notified of malfunction of the motor 340 when the operation of the motor is not completely stopped within a predetermined length of time upon receiving an interruption command from the microprocessor 360. Therefore, the user can repair the motor in advance without damaging 10 the motor or any other component of the washer. Embodiment (4) FIG. 4 illustrates a method of interrupting (braking) operation of a motor in a washer according to a fourth embodiment of the present invention. The washer includes a 15 motor rotating a tub or an agitator, a microprocessor generating control signals to control operation of the motor. Refering to FIG. 4, the microprocessor of the washer initially increases the speed of the motor W (S41 1). When W is determined to be greater or equal to a first predetermined speed Wi (S412), the microprocessor turns the motor power off (S413). On the other hand, if W is determined to be less than Wi in step S412 and if 20 interruption of the motor operation is ordered (S414), the microprocessor interrupts (brakes) the motor operation based on a slow-brake logic (S415). The interruption of the motor operation gets ordered when a user inputs a command for interrupting (braking) the motor operation by turning the power of the washer off, opening a washer door, or manually touching a key control panel.

- 12 After the motor power is turned off in step S413, power-free rotation of the motor occurs and thereby W gradually decreases (S416). If the microprocessor determines that the microprocessor determines whether W is less than or equal to a second predetermined speed W2 being less than Wi (S417), it determines the weight of a load of clothes being 5 contained in the tub by measuring T that represents a length of time that it takes for W to decrease from Wi to W2 (S418). On the other hand, if W is determined to be still greater than W2 in step S417 and if interruption of the motor operation is ordered (S419), step S4 15 is repeated. After the load weight is determined in step S418, the microprocessor increases W 10 (S420). If W is determined to be greater than or equal to a third predetermined speed W3 which is greater than Wi (S421), the microprocessor further increases W (S423). On the other hand, if W is determined to be less than W3 in step S421 and if interruption of the motor operation is ordered (S422), step S415 is repeated. Referring back to step S423, if W is determined to be greater than or equal to a fourth predetermined speed W4 which is 15 greater than W3 (S424), the microprocessor maintains the motor speed to W4 and performs a spin cycle (S425). If W is determined to be less than W4 in step S424 and if interruption of the motor operation is ordered (S426), the microprocessor selects one of a plurality of rapid-brake logics on the basis of T measured in step S4 18 and interrupts or brakes the motor operation 20 according to the selected rapid-brake logic (S427-S432). For example, if T is determined to be less than or equal to a first predetermined length of time Ti (S427), the microprocessor brakes the motor operation based on a first rapid-brake logic (S428). And if T is determined to be greater than Ti but less than or equal to a second predetermined length of time T2 (S429), the motor operation is interrupted based on a second rapid-brake logic 25 (S430). In other words, if T is determined to be greater than an (n-l)th predetermined - 13 length of time Tn-i but less than or equal to an nth predetermined length of time To where n 2, 3,4, ... N (S431), the microprocessor brakes the motor operation based on an nth rapid-brake logic (S432). Referring back to step S425, if a spin period, during which W4 is maintained, is 5 determined to be greater than or equal to a predetermined period of time E (S433), the microprocessor tums off the motor power (S434). On the other hand, if the spin period is determined to be less than E in step S433 and if interruption of the motor operation is ordered (S435), the microprocessor selects on of the plurality of rapid-brake logics on the basis of T measured in step S428 and interrupts the motor operation according to the 10 selected rapid-brake logic (S427-S432). After the motor power is tumed off in step S434, if the microprocessor determines in step S436 that W is less than or equal to W3 and if interruption of the motor operation is ordered (S438), step 415 is repeated. In addition, if W is determined to be greater than W3 in step S436 and if interruption of the motor operation is ordered (S437), steps S427 to S432 are repeated. 15 In the method of interrupting operation of the washer motor shown in FIG. 4, an appropriate motor brake logic is selected based on the weight of the load of clothes so that the optimal interruption of the motor operation can be achieved while avoiding any damage on the motor or any other components that associate with the motor. 20 Embodiment (5) FIG. 5A illustrates a control system that drives a motor provided in a washer according to a fifth embodiment of the present invention. Referring to FIG. 5A, the control system includes a transformer 54 having a converter 54A and a first capacitor Ci for converting the AC power generated by the AC power source 52 into DC power, a switch 25 52A connecting or disconnecting the AC power source 52 to the transformer 54, and a - 14 switching mode power supply (SMPS) unit 56 transforming the DC voltage converted by the transformer 54 into a voltage having a predetermined level. The motor control system shown in FIG. 5A further includes a relay unit 56A which is connected between the SMPS unit 56 and the AC power source 52 and cuts off 5 the AC power if its frequency is higher than a predetermined frequency value, a first resistor Ri connected to the relay unit 56A in parallel, a motor 51 rotating a tub or an agitator in the washer, a driving circuit 58 driving the motor 51 by supplying the voltage converted by the SMPA unit 56 to the motor 51, a microprocessor 59 controlling operation of the motor 51, an insulated gate bipolar transistor (IGBT) 57 performing pulse width 10 modulation upon receiving a control signal from the microprocessor 59, a voltage comparator 53 comparing the reverse voltage generated by the motor 51 during a motor brake with a predetermined voltage value, and a braking resistor 55 dissipating the reverse voltage generated by the motor 5 1 into heat so as to prevent possible circuit damages due to the reverse voltage. 15 Reference will now be made in detail to a method of controlling a motor in a washer according to the fifth embodiment of the present invention, which is illustrated in FIG. 5B. Referring to FIG. 5B, when the microprocessor 59 determines that any one of the conditions for braking operation of the motor 51 is met, it sends interruption signals to the motor driving circuit 58, which then applies phase-reversed input voltages to the motor 51 20 (S5 11). In step S5 11, the reverse voltages are then generated by the motor 5 1 due to its rotation and they are applied to the driving circuit 58. In a case where the motor 51 is driven by three input voltages having three different phases, the reverse voltages generated by the motor 5 1 during the motor brake also have three phases. Therefore, the phases of the reverse voltages depend on the phases of the input voltages that the driving circuit 58 25 applies to the motor 51.

- 15 After the reverse voltages are generated by the motor 51 in step S5ll , the microprocessor 59 measures the reverse voltages generated in step S5 II and determines whether the measured reverse voltages are greater than a predetermined voltage value Vi (S512). If they are, the microprocessor 59 generates control signals for a normal motor 5 brake, in which the braking resistor 55 is allowed to dissipate energy due to the reverse voltages generated by the motor 51 into heat (S513). Otherwise, steps S5l I and S5l2 are repeated until the reverse voltages are determined to be greater than Vi. Next, the microprocessor 59 measures a current-flow period of the braking resistor 55 which represents a length of time that a reverse current flows through the braking 10 resistor 55 when the reverse voltages are generated by the motor 51, and it further determines whether the measured current-flow period is less than a normal dissipate period Ti (S514). Ti represents a period of time that it takes to dissipate all the reverse voltages by the braking resistor 55 in a normal condition. If the measured current-flow period is less than Ti, the microprocessor 59 determines that the braking resistor 55 is opened. 15 If the measured current-flow period is determined to be not less than the Ti, the microprocessor 59 determines whether the measured current-flow period is greater than Ti (S515). If the measured current-flow period is greater than Ti, it determines that the braking resistor 55 is shorted. If it is determined that the measured current-flow period is less than or greater than Ti in step S514 or S515, the microprocessor 59 shorts a 20 corresponding node connected to the driving circuit 58 for a predetermined period of time so as to reduce the reverse voltages generated by the motor 51 (S516). When the node connected to the driving circuit 58 is shorted, the reverse voltages of the motor 51 are reduced due to their phase differences. By doing so, any circuit damage caused by high reverse voltages of the motor 51 can be prevented during the motor brake.

16 After the reverse voltages are reduced in step S516 or the measured current-flow period of the braking resistor 55 is determined to be not greater than Ti in step S5 15, the microprocessor 59 measures the reverse voltages of the motor 51 again and determines whether the measured reverse voltages are less than the predetermined voltage value V 1 5 (S517). If they are, the microprocessor 59 terminates the operation of the motor 51 (S518). Embodiment (6) FIG. 6A illustrates a control system that drives a motor provided in a washer according to a sixth embodiment of the present invention. As shown in FIG. 6A, the 10 system includes a rectifier 611 rectifying the AC power, a motor 612 rotating a tub or an agitator of the washer, and a driving circuit 613 comprising a plurality of insulating gate bipolar transistors (IGBT). The driving circuit 613 applies input voltages U, V, and W having three different phases, respectively, to the motor 612 in a first operation mode and applies phase-reversed voltages to the motor 612 in a second operation mode so that the 15 reverse voltages generated by the motor 612 due to its rotation are applied to the driving circuit 613. The system shown in FIG. 6A further includes a switching mode power supply (SNIPS) unit 614 transforming the output of the rectifier 611 into a voltage having a predetermined level (e.g., 5V), a speedometer 615 measuring the rotational speed of the 20 motor 612, a braking resistor Rb dissipating the reverse voltages generated by the motor 612 into heat so as to prevent possible circuit damages, and a transistor Ti driving the braking resistor Rb. The system further includes a voltmeter 616 that measures the output voltage of the rectifier 611 after the reverse voltage of the motor 612 is dissipated in Rb, a driver microprocessor 617 controlling operations of the driving circuit 613 and the 25 transistor Ti on the basis of the output voltage measured by the voltmeter 616, a door - 17 opening sensor (not illustrated) detecting opening of a washer door and sending a corresponding signal to the drive microprocessor 617, a user interface unit 618 having at least one a touch panel and a key input unit for receiving operational commands from a user, a display unit (e.g., LCD) 619 displaying a message indicating the operation status of 5 the washer, a sound generating unit 620, and a main microprocessor 621 controlling the drive microprocessor 617 so as to operate various components of the washer including the motor 612 according to the operational commands received by the user interface unit 618. The main microprocessor unit 621 detects an abnormal output voltage of the rectifier 611 by communicating with the drive microprocessor 617 and generates control 10 signals to the display unit 619 and the sound generating unit 620 so as to display a warning message and a warning sound indicating the abnormal output voltage of the rectifier 611. Because the brake resistor Rb is detachably provided in the control system as shown in FIG. 6A and the voltmeter 616 measures the output voltage of the rectifier 611 using Rb, the output voltage of the voltmeter 616 will be OV if Rb is not provided at all or the connector 15 622 is inoperatively provided. Reference will now be made in detail to the operation of the control system shown in FIG. 6A. When a user inputs commands for a wash cycle through the user through interface unit 618, the main microprocessor 621 transmits control signals to the drive microprocessor 617 so as to drive various components of the washer based on a plurality of 20 operation parameters corresponding to a wash option selected by the user. The drive microprocessor 617 initially rotates the motor 612 while monitoring the speed of the motor 612 and performs the wash cycle by operating other components such as a water supply system and a water drain system. On the other hand, the main microprocessor 621 generates control signals to the display unit 619 for displaying a current operation status of - 18 the washer and to the sound generating unit 620 for generating a warning sound if necessary. During a wash cycle, the rotational direction of the motor 612 alternates between a clockwise direction and a counter-clockwise direction. For example, in order to switch the 5 direction of the motor 612 which was initially rotating in a clockwise direction in a first mode, the rotation of the motor 612 must be initially stopped. In addition, such brake or interruption of the motor operation is often necessary when a washer door is opened by a user during a spin (dehydration) cycle. Therefore, when the drive microprocessor 617 determines that any one of the conditions for braking the motor operation is met, it 10 operates the driving circuit 613 in a second operation mode, in which the driving circuit 613 applies phase-reversed input voltages to the motor 612 and the brake resistor Rb operates to dissipates the reverse voltage generated by the motor 611 so as to prevent any circuit damages. FIG. 6B is a flow chart illustrating a method of controlling a motor in a washer 15 according to the sixth embodiment of the present invention. Initially, the drive microprocessor 617 measures the output voltage of the rectifier 611 using the voltmeter 616 (S61). Next, if the drive microprocessor 617 determines that the measured output voltage is OV (S62), it transmits to the main microprocessor 621 a warning signal indicating that the brake resistor Rb is not connected at all or is improperly connected. 20 Because the voltmeter 611 measures the output voltage of the rectifier 611 passing through Rb using a pair of resistors Ri and R2 connected in series, the measured voltage of OV indicates that the power source voltage is being applied but Rb is improperly connected. Upon receiving the warning signal from the drive microprocessor 617, the main microprocessor 621 generate controls signals to the display unit 619 and the sound 25 generating unit 620 for displaying a warning message indicating Rb is improperly - 19 connected and for generating a warning sound (S63). If it is determined in step S62 that the output voltage is not OV, step S63 is skipped. Next, if the main microprocessor 621 determines that operational commands for a wash cycle are inputted by a user through the user interface unit 618 (S64), it further measures the output voltage of the rectifier 611 5 using the voltmeter 616 and determines whether the measured output voltage is OV (S65). If it is, the main microprocessor does not initiate the wash cycle but repeats step S65 afier being in a standby mode for a predetermined period of time. This step is essentially important for preventing any chance of damaging the control system shown in FIG. 6A. On the other hand, if it is determined in step S65 that the measured output voltage 10 is not OV (meaning that Rb is now properly connected), the main microprocessor 621 initiates the wash cycle by generating control signals to the drive microprocessor 617 so as to operate various components of the washer including the motor 621 according to the operational commands received from the user (S26). 15 Embodiment (7) FIG. 7A illustrates a control system controlling a motor in a washer according to a seventh embodiment of the present invention. Referring to FIG. 7A, the control system includes a motor 71 rotating a tub or an agitator of the washer, a transformer 72 generating a DC power voltage, and a motor driving unit 73 driving the motor 71 by applying the DC 20 power voltage to the motor 71. The control system shown in FIG. 7A further includes a timer 74 counting a predetermined deceleration period, a voltmeter 75 measuring the reverse voltages generated due to reverse currents generated by the motor 71 when interrupted, and a microprocessor 76 that generates a control signal to the driving unit 71 to decrease the motor speed if the measured reverse voltages are less than a predetermined 25 voltage value.

- 20 The microprocessor 76 initially accelerates the motor speed and controls the timer 74 to repeatedly count a predetermined deceleration period so as to reduce the initially accelerated motor speed for each deceleration period. In addition, the microprocessor 76 measures the DC input voltage of the motor driving unit 71 for each deceleration period 5 and maintains a standby status to reduce the input voltage of the driving circuit 71 if the measured input voltage is higher than a predetermined voltage level. The voltmeter 75 is connected to the DC link in parallel and includes three resistors which are connected in sees. Therefore, the output of the voltmeter 75 is a voltage subdivided by the resistors of the voltmeter 75. 10 On the other hand, if the measured DC voltage of the driving unit 71 is less than the predetermined voltage level, the microprocessor 76 measures the current leading phase angle 4) and reduces the motor speed by reducing the leading phase angel by a predetermined rate for each deceleration period. If the leading phase angle q) becomes zero, the microprocessor 76 obtains the current pulse width modulation (PWM) duty and 15 reduces the motor speed by reducing the PWM duty by a predetermined rate for each deceleration period. Reference will now be made in detail to a method of controlling a motor in a washer according to the seventh embodiment of the present invention, which is illustrated in FIG. 7B. When the algorithm shown in FIG. 7B starts, the microprocessor 76 sends to a 20 control signal to the timer 74 to start measure a time T and determines whether a predetermined deceleration period Te is elapsed by checking whether T is greater than Te (S70 1). If Te is elapsed, the microprocessor 76 initializes the timer 74 by setting T to zero (S702) and determines whether the current DC voltage V of the driving unit 71 is less than or equal to a predetermined voltage level Vc (S703). If it is deter-mined in step S703 that V 25 Vc, then the microprocessor 76 measures the current leading phase angle <D of the DC - 21 voltage V of the driving unit 71 (S704). If the measured leading phase angle 1 is greater than zero (S705), the microprocessor 76 reduces the leading phase angle 0 by a predetermined level c (S706). Thereafter, if the microprocessor 76 determines that the motor 71 is not stopped (S71 1), step S701 and all the following steps are repeated again as 5 shown in FIG. 7B. On the other hand, if it is determined in step S705 that the measured leading phase angle $ is not greater than zero, the microprocessor 76 further determines whether the measured leading phase angle (1) is equal to zero (S707). If it is equal to zero, the microprocessor 76 obtains the current PWM duty (S708). If the current PWM duty is 10 greater than zero (S709), it reduces the P\W'M duty by a predetermined level P. Next, if it determines that the motor is not stopped (S71 1), all the previous steps are repeated again. In addition, if it is determined in step S704 that the measured DC voltage V is greater than V,, steps S704 to S719 are skipped and step S7 II is performed. 15 Embodiment (8) FIG. 8A illustrates an apparatus of controlling operation of a motor in a washer according to an eighth embodiment of the present invention. Referring to FIG. 8A, the apparatus includes a key input unit 810 receiving commands from a user for a wash cycle, a motor 830 rotating a tub and/or an agitator of the washer, and a controller 820 generating 20 control signals to perform the wash cycle according to a wash option selected by the user and to lock a wash door (not illustrated) if the speed of the motor 830 is equal to a predetermined speed. The apparatus shown in FIG. 8A further includes a washer door locking unit 850 that locks or unlocks the washer door of the washer, a speed measuring unit (e.g., a speedometer) 840 measuring the rotating speed of the motor 830 and providing 25 the measured speed to the controller 820, and a display unit 860 that displays a message -- 22 indicating the locking status of the washer door upon receiving a control signal from the controller 820. When a user inputs commands for a wash cycle through the key input unit 810, the controller 820 generate control signals to perform a wash cycle, a rinse cycle, and a spin 5 (dehydration cycle). After the spin cycle is initiated, the controller 820 generates a control signal to the wash door locking unit 850 to lock the washer door when the speed of the motor 830 reaches a first predetermined motor speed. When the speed of the motor further reaches a second predetermined motor speed, the controller 820 maintains the speed of the motor 830 until the spin cycle is finished. 10 Reference will now be made in detail to a method of controlling operation of a motor in a washer according to the eighth embodiment of the present invention. Referring to FIG. 8B, if the controller 820 determines that a spin cycle (dehydration cycle) is ordered (S801), it increases the speed W of the motor 830 (S802). Next, if the cont-roller 820 determines that W is equal to a first predetermined motor speed Wi, e.g., 700 RPM (S803), 15 it sends a control signal to the washer door locking unit 850 to lock the washer door of the washer (S804). If W is determined to be less than Wi in step S803, the controller 820 repeats step S802 until W becomes Wi. After the washer door is locked in step S804, the controller 820 further increases the motor speed W (S805). If it is determined that W has reached a second predetermined motor speed W2, e.g., 1000 RPM, which is greater than 20 Wi (S806), the controller 820 maintains the motor speed W until the spin cycle is finished (S807 and S808). As described above, the controller 820 does not lock the washer door until the speed of the motor 830 reaches to the first predetermined motor speed Wi so that the power consumption and durability of the door lock are greatly improved. 25 Embodiment (9) - 23 FIG. 9A illustrates a control system that drives a motor provided in a washer according to a ninth embodiment of the present invention. The motor control system shown in FIG. 9A illustrates a rectifier 911 rectifying the AC power, a motor 912 rotating a tub or an agitator of the washer, and a driving circuit 913 comprising a plurality of 5 insulating gate bipolar transistors (IGBT). The driving circuit 913 applies input voltages U, V, and W having three different phases, respectively, to the motor 912 in a first mode and applies phase-reversed voltages to the motor 912 in a second mode so that the reverse voltages generated by the motor 912 due to its rotation are applied to the driving circuit 913. 10 The control system shown in FIG. 9A further includes a switching mode power supply (SMPS) unit 914 transforming the output of the rectifier 911 into a voltage having a predetermined level (e.g., 5V), a speedometer 915 measuring the rotational speed of the motor 912, a braking resistor Rb dissipating the reverse voltages generated by the motor 912 into heat so as to prevent possible circuit damages, and a transistor Ti driving the 15 braking resistor Rb. The control system further includes a voltmeter 916 measuring the output voltage of the rectifier 911 after the reverse voltages of the motor 912 are dissipated in Rb, a microprocessor 917 controlling operations of the driving circuit 913 and the transistor Ti on the basis of the output voltage measured by the voltmeter 916, and a door opening sensor (not illustrated) detecting opening of a washer door and sending a 20 corresponding to the microprocessor 917. Reference will now be made in detail to a method of controlling a motor in a washer according to the ninth embodiment of the present invention, which is illustrated in FIG. 9B. Referring to FIG. 9B, when a user inputs commands for washing a load of clothes to be washed, the microprocessor 917 operates the driving circuit 913 so as to rotate the 25 motor 912 based on a wash algorithm or program that correspond to the user input -- 24 commands so that a tub and an agitator of the washer are rotated for performing wash and rinse cycles. Thereafter, the microprocessor 917 initiates a spin (dehydration) cycle by increasing the speed of the motor 912 (S931). The speed of the motor 912 in a spin cycle should be determined based on a total weight of the load of clothes to be dehydrated or 5 weight distribution of the load, but is typically greater than 100 rpm. After a spin cycle is initiated in step S931, the microprocessor 917 determines whether a motor brake is necessary by determining any one of the conditions for braking motor operation is met (S932). For example, if a motor interruption command inputted by a user or a signal indicating opening of a washer door is received, or if the speed of the 10 motor 912 measured by the speedometer 915 is determined to be abnormal, the microprocessor 917 determines that interruption (brake) of the motor operation is necessary. If any one of such conditions is met, the microprocessor 917 determines whether the current speed W of the motor 912 is greater than a first critical speed Wi (S933). Wi (typically set to 1000 rpm) represents the minimum speed of the motor 912 that 15 can mechanically damage the motor 912 or any other components that associate with the motor 912 (e.g., a clutch) when a rapid brake of the motor operation is performed. If it is determined in step S933 that W is greater than Wi, the microprocessor 917 controls the driving circuit 913 to short power input terminals of the motor 912 for a predetermined period of time in order to brake the motor operation (S934). By doing so, rather a slow 20 motor brake is achieved so that any mechanical damage due to a rapid motor brake can be prevented. Next, the microprocessor 917 further determines whether the current speed W of the motor 912 is less than Wi and is greater than a second critical speed W2 (S935). W2 (typically set to 100 rpm) represents the allowable speed of the motor 912 that does not 25 create any mechanical damage even if a rapid brake of the motor operation is performed. If - 25 it is determined in step S935 that W is less than Wi and is greater than W2, then microprocessor 917 performs a rapid motor brake by operating the driving circuit 913 to apply phase-reversed voltages to the motor 912 for a predetermined period of time and by operating the brake resistor Rb so as to dissipate the reverse voltages generated by the 5 motor 912 during the rapid motor brake (S936). In the method shown in FIG. 9B, a same rapid brake is performed when W is in a signal speed range of Wi to W2. However, different rapid brakes can be performed for a plurality of subdivided ranges of the motor speed by using different duty rations when applying the phase-reversed voltages to the motor 912. 10 Furthermore, the microprocessor 917 further determines whether the current speed W of the motor 912 is less than W2 (S937). If it is, the microprocessor 917 controls the driving circuit 913 to short the power input terminals of the motor 912 in order to brake the motor operation (S938). Since W is less than 100 rpm, the motor operation can be easily. Thereafter, if the microprocessor 917 determines that the motor operation is terminated 15 (S939), then it ends the motor control algorithm. Otherwise, steps S933 to S939 are repeated. Referring back to step S932, if none of the conditions for braking motor operation are met and if the spin cycle is determined to be terminated in step S940, the microprocessor 917 ends the motor control algorithm. 20 Embodiment (10) FIG. 10 illustrates a circuitry for limiting a motor current in an electrical appliance according to a tenth embodiment of the present invention. Referring to FIG. 10, the current limiting circuitry includes a microprocessor 999, a power source Vcc supplying a source 25 voltage of 5V, a first resistor Ri having a resistance of 33 k and a dip switch 997 - 26 connected between the power source Vcc and a ground in series, a capacitor Ci connected to the dip switch 997 in parallel, an op amp 998 having an inverting input connected to a node between RI and the dip switch 997 and an output connected to the microprocessor 999, and a third resistor R3 having a resistance of 0.027 k , which is connected between 5 the noninverting input of the op amp 998 and a ground. Reference will now be made in detail to the operation of the current limiting circuitry shown in FIG. 10. The dip switch 997 comprises a plurality of resistors having different resistances (e.g., 1.3 k , 1.5 k , 1.8 k , 2.0 k , and so on). Therefore, an appropriate one of the plurality of resistors can be conveniently selected for selecting a 10 limited current value. For example, if a resistor having a resistance of 1.3 k is selected by the dip switch 997, then the limited current that flows through R3 is 1= {(5*1.3)/(33+1.3)}/0.027 = 7 A. Alternatively, if a resistor having a resistance of 1.8 k is selected by the dip switch 997, the limited current that flows through R3 is 15 I={(5* 1 8)/(33+1.8)}/0.027 = 9A. As shown in the examples shown above, the value of the limited current that flows through R3 is varied based on the switching of the dip switch 997. When more than one resistors are selected by the dip switch 997, the value of the current that flows through R3 can be even lower since the selected resistors are in parallel. Instead of using the dip switch 20 997, a resistance-variable resistor can be used. However, it has a disadvantage that it is difficult to set a precise resistance value of the resistance-variable resistor. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications Q \OPER\GCP\2M6212342c doc-20/04/2m9 - 27 and variations of this invention provided they come within the scope of the appended claims and their equivalents. The reference in this specification to any prior publication (or information derived from it), 5 or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. 10 Throughout this specification and claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. 15

Claims (12)

1. A method of controlling a motor-driven washing machine, the method comprising the steps of: 5 initiating a wash cycle by operating a motor provided in the washing machine according to a washing option selected by a user; generating a motor-brake signal to brake the operation of the motor when a motor interruption command is generated and measuring a brake period which represents a total length of time it takes to completely stop the operation of the motor; 10 determining malfunction of the motor based on whether the measured brake period exceeds a predetermined period of time; and displaying a warning message on a display unit, the message indicating the determined malfunction of the motor. 15

2. The method of claim 1, wherein the determining step comprises the steps of: storing the measured brake period in a memory if the measured brake period exceeds the predetermined period of time; determining whether a total number of brake periods stored in the memory until the present time is greater than a threshold frequency value; 20 determining the malfunction of the motor if the total number of the stored brake periods is greater than the threshold frequency value.

3. The method of claim 1, wherein the motor-interruption command is generated when the user manually touches a key control panel or opens a washer door of the washing 25 machine during the wash cycle.

4. The method of claim 1, further comprising the step of continuing the wash cycle according to the washing option selected by the user if the measured brake period is less than the predetermined period of time. 30 P:\opercp\2001230345dw I spdo.c-3f5O6 - 29 5. The method of claim 1, wherein the initiating step includes the step of rotating the motor so as to rotate a washing tub or an agitator provided in the washing machine according to the washing option selected by the user.

5

6. A control system for a washing machine, the control system comprising: a motor rotating a washing tub or an agitator provided in the washing machine according to a washing option selected by a user; a microprocessor operatively coupled to the motor for braking operation of the motor when a motor-interruption command is generated and measuring a brake period 10 which represents a total length of time it takes to completely stop the operation of the motor, the microprocessor determining malfunction of the motor based on whether the measured brake period exceeds a predetermined period of time; and a display unit displaying a warning message indicating the determined malfunction of the motor upon receiving a control signal from the microprocessor. 15

7. The control system of claim 6, further comprising a memory storing the measured brake period if the measured brake period exceeds the predetermined period of time.

8. The control system of claim 7, wherein the microprocessor determines the 20 malfunction of the motor if a total number of brake periods that are stored in the memory until the present time is greater than a threshold frequency value.

9. The control system of claim 7, wherein the memory is an EEPROM and the display unit is an LCD. 25 Q:\OPER\GCP\2(X6202342c doc-20A)4/2X09 -30

10. The control system of claim 6, further comprising a timer that measures the total length of time it takes to completely stop the operation of the motor.

11. A method of controlling a motor-driven washing machine, substantially as 5 hereinbefore described with reference to the accompanying drawings.

12. A control system for a washing machine, substantially as hereinbefore described with reference to the accompanying drawings. 10