JP2000014968A - Inverter-driven fully automated washing machine and method for controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter-driven fully automated washing machine capable of obtaining high starting torque while suppressing a starting current. SOLUTION: An operating area from the start of a three-phase induction motor to its operating rotational number is divided into several zones using rotational numbers as parameters in accordance with the relationship between a preset operating rotational number and acceleration time calculated from a current input characteristic during loaded operation, and an operating voltage and frequency are set for each of the zones. In that case, the voltage and frequency are set so that torque characteristic at a maximum frequency is maintained and that an input voltage is held at or below a preset value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fully automatic washing machine driven by an inverter, and more particularly to a fully automatic washing machine driven by an inverter capable of outputting a high starting torque while keeping a starting current value of an electric motor low. And its control method.

[0002]

2. Description of the Related Art FIG. 7 shows the characteristics of a conventional washing machine motor (three-phase induction motor) when current limiter control is not performed and when current limiter control is performed. In this characteristic diagram, the horizontal axis represents the rotation speed (rpm), and the vertical axis represents the current value (A) and the torque (N · cm). When the current limiter control is not performed, the current value is not regulated by the current limiter as can be seen from FIG.
Gradually lower until it rises. In this characteristic, the starting torque is slightly higher than 260 [N · cm], and gradually decreases as the rotation increases to about 1300 [rpm].

On the other hand, in the case of general current limiter control of a home washing machine in which the current limiter is operated at 7 [A], the starting torque is about 160 [N · cm] and 1000 [N · cm].
As the rotation increases to about [rpm], the torque becomes 26
It gradually increases to a little over 0 [N · cm] and 1300 [r
pm], the characteristics gradually decrease when the rotation increases. That is, both characteristics are 1000 [r
pm] and thereafter, but 10 minutes from the start of rotation.
Up to 00 [rpm] is completely different, and when the starting current at which the current value becomes maximum in the former is suppressed as in the latter, it can be seen that the starting torque is significantly reduced in the latter control method.

[0004]

The reason why the current limiter control is performed in spite of the fact that the starting torque is remarkably reduced is that flicker is prevented from occurring during the operation of the washing machine. That is, in a fully automatic washing machine having an operation cycle in which the operation and the stop are repeated in a short cycle, and the normal rotation and the reverse rotation are alternately performed, when the operation is performed without performing the current limiter control as in the former, a large Is flowing, and the current is repeatedly turned on and off in a short cycle, which causes a voltage drop and causes flickering of the electric lamp. On the other hand, a large decrease in the torque means a decrease in the washing capacity of the washing machine.

The present invention has been made in view of such a background, and an object thereof is to provide an inverter-driven fully automatic washing machine capable of obtaining a high starting torque while suppressing a starting current, and a control method thereof. To provide.

[0006]

In order to achieve the above object, the present invention provides a characteristic that a rated torque can be obtained by supplying a frequency corresponding to a rotation speed, in other words, the lower the frequency, the lower the torque. Utilizing the characteristic of an inverter that can obtain a high starting torque with a voltage, the number of rotations when a three-phase induction motor is driven by an inverter and the three-phase induction motor is driven at a single frequency under a constant voltage-
The operation section derived from the torque characteristic (FIG. 7) is divided into a plurality of sections, and the frequency and the voltage are set according to the section, and control is performed so as to obtain a characteristic according to the rotation speed-torque characteristic. .

Specifically, in order to achieve the above object, the first means is to drive the three-phase induction motor by an inverter, repeat the operation and stop in a short time, and alternately perform the normal rotation and the reverse rotation. In the inverter-driven fully automatic washing machine having a cycle, from the relationship between the preset operation speed and the acceleration time obtained from the current input characteristic during load operation, the operation speed from the start of the three-phase induction motor. And a control means for controlling the three-phase induction motor by setting the operating voltage and frequency for each of the divided sections.

[0008] A second means is that, in the first means, the voltage and the frequency are set so as to maintain the torque characteristic at the highest frequency and to make the input power equal to or less than a preset value. Features.

The third means is characterized in that, in the first means, the distribution of the plurality of divided voltages and frequencies is set to an integral multiple of the cycle of each section.

The fourth means is to achieve the above object,
In the method for controlling an inverter-driven fully automatic washing machine using a three-phase induction motor, the three-phase induction motor is determined based on a relationship between a preset operation speed and an acceleration time obtained from a current input characteristic during load operation. The operation section from the start of the operation to the operation speed is divided into a plurality of sections, the torque characteristic at the highest frequency is maintained, and the voltage and frequency are set for each of the divided sections so that the input power is equal to or less than a preset value. Is set to control the three-phase induction motor.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a characteristic diagram showing a rotational speed-torque characteristic of an inverter-driven three-phase induction motor according to an embodiment of the present invention. FIG. 2 is a characteristic diagram showing a rotational speed-input characteristic during frequency and voltage control. FIG. 3 is a characteristic diagram showing a time-current characteristic of the three-phase induction motor during a washing load operation of the washing machine.

As shown in FIG. 1, in the present embodiment, a single frequency and a single voltage (here, the operation speed is 1700 rpm)
m, frequency 68 Hz, voltage 170 V)
The operating section of the torque characteristic is divided into five sections. In the division method, the acceleration time is obtained from the time-current characteristic during the washing load operation shown in FIG. 3, and this acceleration time is assigned to the operation speed of 1700 rpm. That is, here, the operation speed 170
The control is performed on the assumption that the time required to reach 0 rpm is equal to the acceleration time. The acceleration time is 300 ms in the characteristic of FIG. 3, but it goes without saying that this acceleration time actually changes according to the magnitude of the load. In addition, the frequency and voltage of each divided section are 800 W or less from the rotational speed-input characteristic shown by the dotted line in FIG. 2 and the average value of the torque is lower than the torque at the single frequency and single voltage shown by the dotted line in FIG. I tried not to be. In this way, from start to 600 rpm (37 Hz, 119 V) From 600 rpm to 900 rpm (45 Hz, 1
40V) From 900 rpm to 1100 rpm (48 Hz,
(155V) From 1100 rpm to 1340 rpm (60H
(z, 160 V) The range from 1340 rpm to the maximum rotation speed including the operation rotation speed of 1700 rpm is divided into five regions (68 Hz, 170 V), and the frequency and voltage are set in each region as described above.

The number of n at each frequency, that is, the period is 1
1700 [rpm] / 300 [ms] per millisecond ≒ 5.67 [rpm]
m]. When this is converted into the number of revolutions from 27 ms which is a cycle of (frequency of 37 Hz), 5.67 [rpm] × 27 [ms] ≒ 153 [rpm /
Cycle]. Since the section that satisfies the input and the torque is 600 rpm, dividing this by the number of rotations per cycle gives 600 [rpm] / 153 [rpm / cycle] = 3.
9 [cycles]. Therefore, if this 3.9 cycle is approximated to an integer, it becomes 4 cycles, which is represented by n = 4.

Similarly, when the period is calculated from the above frequencies for the other four regions, n = 3 for n = 3 and n = 3 for n = 2. This is 3 cycles in the area of 4 cycles in the area, 3 cycles in the area, 2 cycles in the area.
This shows that during the cycle, the three-phase induction motor may be driven at the frequency and the voltage.

By setting the frequency and the voltage in such a manner as described above, the rotation speed-torque characteristic of the three-phase induction motor is equal to that of the single frequency and single voltage as shown in FIG. 2, and the input is a single frequency indicated by a dotted line as indicated by a solid line in FIG.
It can be seen that the voltage can be significantly reduced as compared with the case of a single voltage.

FIG. 4 is a schematic sectional view showing the structure of a fully automatic washing machine to which such an inverter driving system is applied, FIG. 5 is a circuit diagram showing a schematic configuration of an inverter circuit, and FIG. It is a circuit diagram showing an electric motor.

In FIG. 4, the fully automatic washing machine 100 has a drive mechanism at a lower part and a control mechanism at an upper part. A control circuit (control means) including an inverter circuit 1 as a control mechanism is provided on an upper surface of the main body of the fully automatic washing machine, and controls a three-phase induction motor 2 having a lower drive function. A motor pulley 3 is connected to a shaft of the three-phase induction machine 2 via a V-belt with a clutch pulley 5 so that power can be transmitted to the clutch 6 side. The clutch 6 is provided with a function of switching the operating state between a state in which the power of the three-phase induction motor 2 is rotated by rotating the rotor 7 and a state in which the washing is performed by rotating the spinning tub 8 in accordance with an instruction from the control circuit. ing.

As shown in FIG.
A diode bridge 10 in which two diodes are bridge-connected, an electrolytic capacitor 11 connected in parallel to two output terminals of the diode bridge 10, and two connected in series to output to each phase of the three-phase induction motor 2 Done I
A GBT (insulated gate bipolar transistor) 12 is connected in parallel to the output terminal for each phase, and a drive current is output for each of U, V, and W phases from a connection point of the two IGBTs 12 connected in series. Is done. A commercial power supply (AC 100 V) 9 is connected to an input terminal of the diode bridge 10. A current supplied from the power supply is rectified by the diode bridge 10 to produce a DC power supply, and further smoothed by an electrolytic capacitor 11 to be a DC power supply. , And six IGBTs 12 form a three-phase power supply. The three-phase induction motor 2 includes three windings 13 of U, V, and W. The driving current output from each connection point of the IGBT 12 described above is applied to each of the windings 13 of U, V, and W of the three-phase induction motor 2. Supplied to In this embodiment, the V and W phase windings 1
3 is provided with a protection device 14 for preventing overload.

By performing predetermined control through the inverter circuit 2 at the cycle set as described above, a fully automatic washing machine can be operated with a high starting torque and a low starting current (low input). . This makes it possible to exhibit high washing performance in energy saving operation, and also to prevent flickering of the electric lamp due to a decrease in voltage.

[0021]

As is apparent from the above description, according to the present invention, the three-phase induction is obtained from the relationship between the preset operation speed and the acceleration time obtained from the current input characteristic during load operation. The operating section from the start of the motor to the operating speed is divided into a plurality of sections, and control means for controlling the three-phase induction motor by setting the operating voltage and frequency for each of the divided sections is provided. It is possible to perform an operation that obtains a high starting torque while suppressing it.

Further, since a high starting torque can be obtained while suppressing the starting current, the starting current does not increase, thereby preventing flickering due to a decrease in voltage.

Furthermore, according to the present invention, the operation from the start of the three-phase induction motor to the operation speed is determined from the relationship between the preset operation speed and the acceleration time obtained from the current input characteristic during load operation. Dividing the section into a plurality of sections, maintaining the torque characteristics at the highest frequency, and controlling the three-phase induction motor by setting the voltage and frequency for each of the divided sections so that the input power is equal to or less than a preset value. Therefore, a high starting torque can be obtained while suppressing the starting current, thereby enabling energy saving operation.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a rotation speed-torque characteristic of an inverter-driven fully automatic washing machine according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an embodiment of the present invention, a frequency at a single frequency and a single voltage, and a rotation speed-input characteristic at the time of voltage control.

FIG. 3 is a diagram showing a time-current characteristic of a motor during a washing load operation.

FIG. 4 is a schematic sectional view showing a configuration of an inverter-driven fully automatic washing machine according to an embodiment of the present invention.

FIG. 5 is a circuit diagram schematically illustrating an inverter circuit according to an embodiment of the present invention.

FIG. 6 is a circuit diagram of the three-phase induction motor according to the embodiment of the present invention.

FIG. 7 is a characteristic diagram for explaining a rotation speed-torque characteristic of a current limiter control conventionally performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter circuit 2 Three-phase induction motor 9 Commercial power supply 10 Diode bridge 11 Electrolytic capacitor 12 IGBT 13 Winding 100 Fully automatic washing machine

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Shoichi Ito 1-1-1 Higashitaga-cho, Hitachi City, Ibaraki Prefecture F-term in Tachitaga Technology Co., Ltd. (Reference) 3B155 AA10 BA11 EA12 HB10 HB19 HB26 HC05 KA34 KB08 LB16 LB17 LC02 LC04 LC13 LC15 LC33 MA07 5H576 AA12 BB02 BB05 BB10 DD02 DD04 EE10 EE17 HA04 HB01 MM04 PP01

Claims (4)

[Claims] 1. A preset operation in an inverter-driven fully automatic washing machine having an operation cycle in which a three-phase induction motor is driven by an inverter, repeats operation and stop in a short time, and alternately performs forward rotation and reverse rotation. Based on the relationship between the rotation speed and the acceleration time obtained from the current input characteristic during load operation, the operation section from the start of the three-phase induction motor to the operation rotation number is divided into a plurality of sections, and the operation is performed for each of the divided sections. And a control means for controlling the three-phase induction motor by setting a voltage and a frequency to be driven. 2. The inverter drive according to claim 1, wherein the voltage and the frequency are set so that the torque characteristics at the highest frequency are maintained and the input power is equal to or less than a preset value. Fully automatic washing machine. 3. The inverter-driven fully automatic washing machine according to claim 1, wherein the distribution of the divided voltage and frequency is set to an integral multiple of the cycle of each section. 4. A method of controlling an inverter-driven fully automatic washing machine using a three-phase induction motor, comprising: a step of determining a relationship between an operation speed set in advance and an acceleration time obtained from a current input characteristic during load operation; The operation section from the start of the three-phase induction motor to the operation speed is divided into a plurality of sections, the torque characteristic at the highest frequency is maintained, and the divided section is such that the input power is equal to or less than a preset value. Controlling the three-phase induction motor by setting a voltage and a frequency for each of the three-phase induction motors.