JP4238489B2 - Motor drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor drive device that drives a motor by an inverter circuit.
[0002]
[Prior art]
In recent years, there has been proposed a DC brushless motor that is driven by an inverter device to shorten time during braking and improve the reliability of the braking device.
[0003]
Conventionally, this type of braking device has been configured as shown in Japanese Patent Laid-Open No. 2001-46777. That is, a DC brushless motor that directly drives the dehydration tank is driven by generating a sinusoidal three-phase AC voltage waveform from the output signal of the rotor position detection means comprising the Hall IC by the inverter circuit, and during dehydration operation braking, The DC power supply voltage of the inverter circuit was lowered by the DC voltage variable power supply, and a voltage vector having a phase opposite to the induced voltage phase was generated to perform a braking operation.
[0004]
[Problems to be solved by the invention]
However, in such a conventional configuration, voltage regeneration to the DC power supply of the inverter circuit due to the motor-induced voltage occurs, so it is necessary to reduce the DC power supply voltage of the inverter circuit, and thus a variable DC power supply circuit is necessary and expensive. Further, there is a drawback that the motor current during braking operation increases and the power semiconductor of the motor or the inverter device rises in temperature.
[0005]
The present invention solves the above-described conventional problems, and the inverter output voltage phase is adjusted during braking. Around 90 degrees Advance Further, the inverter circuit output voltage phase is advanced to around 180 degrees. The purpose of this is to perform a highly efficient braking operation in which the generated energy is consumed by the motor resistance by preventing the increase of the regenerative voltage due to the motor induced voltage and the motor current is reduced.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention drives a motor by converting DC power of a rectifier circuit connected to an AC power source into AC power by an inverter circuit, Made of permanent magnets Rotor of The inverter circuit is controlled by the rotor position detecting means for detecting the position and the control means to drive the motor in a sine wave. During braking, the control means changes the inverter circuit output voltage phase from the induced voltage phase of the motor. Around 90 degrees After advancing and lowering the torque, the motor applied voltage phase is further advanced to around 180 degrees to generate braking torque.
[0007]
As a result, the energy generated by the motor braking operation during high-speed rotation is consumed by the resistance of the motor, and the braking operation can be performed without increasing the DC voltage of the inverter circuit. Since it is applied, the motor current at the time of braking can be reduced, the temperature rise of the motor and the power semiconductor at the time of braking is reduced, and a highly reliable braking operation is possible.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The invention according to claim 1 of the present invention is driven by an AC power source, a rectifier circuit connected to the AC power source, an inverter circuit that converts DC power of the rectifier circuit into AC power, and the inverter circuit. A motor and the motor Made of permanent magnets Rotor of Rotor position detecting means for detecting the position, and control means for controlling the inverter circuit, wherein the control means is configured to set the inverter circuit output voltage phase to be higher than the induced voltage phase of the motor. Around 90 degrees Advance Further, the inverter circuit output voltage phase is advanced to around 180 degrees. The braking torque is generated by the motor, and the braking torque can be generated in the motor with a small current without causing the induced voltage of the motor to be regenerated to the DC power source side. The voltage rise of the power semiconductor can be prevented.
[0009]
Claim 2 In the invention described in claim 1, in the invention described in claim 1, the control means brakes the inverter circuit so that the inverter circuit output voltage is larger than the motor induced voltage during low-speed rotation of the motor. At the time of rotation, the motor current is mainly caused to flow by the inverter circuit voltage to generate the braking torque, so that it is possible to prevent the braking torque from being lowered during the low-speed rotation.
[0010]
Claim 3 In the invention described in claim 1, in the invention described in claim 1, the control means continuously advances the inverter circuit output voltage phase from the initial phase to near 180 degrees to maintain the phase. Yes, it is possible to prevent an excessive voltage increase in the inverter circuit and abnormal motor noise when the phase is changed instantaneously during motor rotation.
[0011]
【Example】
Hereinafter, embodiments of the washing machine according to the present invention will be described with reference to the drawings.
[0012]
Example 1
As shown in FIG. 1, the AC power supply 1 applies AC power to the rectifier circuit 3 via the line filter 2 and converts the AC power into DC power by the rectifier circuit 3. The rectifier circuit 3 constitutes a voltage doubler rectifier circuit. When the AC power supply 1 is a positive voltage, the capacitor 31a is charged by the full-wave rectifier diode 30, and when the AC power supply 1 is a negative voltage, the capacitor 31b is charged and connected in series. A double voltage DC voltage is generated at both ends of the capacitors 31a and 31b, and the double voltage DC voltage is applied to the inverter circuit 4.
[0013]
The inverter circuit 4 is constituted by a three-phase full-bridge inverter circuit composed of six power switching semiconductors and an antiparallel diode, and normally includes an insulated gate power transistor (IGBT), an antiparallel diode, its driving circuit, and a protection circuit. It consists of an intelligent power module (hereinafter referred to as IPM). A motor 5 is connected to the output terminal of the inverter circuit 4 to drive a stirring blade (not shown) or a washing and dewatering tub (not shown).
[0014]
The motor 5 is constituted by a direct current brushless motor, and the relative position (rotor position) between the permanent magnet and the stator constituting the rotor is detected by the rotor position detecting means 5a. The rotor position detecting means 5a is usually composed of three Hall ICs. A current detection means 6, a so-called shunt resistor, is connected between the negative voltage terminal of the inverter circuit 4 and the negative voltage terminal of the rectifier circuit 3.
[0015]
Between the output AC voltage terminals of the line filter 2, a water supply valve 7, a drain valve 8, and a clutch 9 are connected and controlled by the switching means 10. The water supply valve 7 supplies tap water to the washing / dehydrating tub and is constituted by an electromagnetic valve, and the drain valve 8 controls the drainage of the water in the washing / dehydrating tub. The clutch 9 controls whether the rotational drive shaft of the motor 5 is coupled to the stirring blade or the washing and dewatering tub. The switching means 10 is configured by a solid state relay such as a bidirectional thyristor or a mechanical relay.
[0016]
The control circuit 11 controls the inverter circuit 4 and the switching means 10, and controls the IPM of the inverter circuit 4 by the control means 12 constituted by a microcomputer and the output signal of the control means 12 to drive the motor 5 to rotate. An inverter driving circuit 13 for controlling, a switching means driving circuit 14 for controlling the switching means 10, and a current for detecting the current of the inverter circuit 4 from the output signal of the current detecting means 6 and applying a signal corresponding to the motor current to the control means 12 It comprises a detection circuit 15. In addition to the A / D conversion circuit of the control means 12, the microcomputer controls the output current of the inverter circuit 4 by a signal corresponding to the A / D converted motor current.
[0017]
The control means 12 includes a carrier signal generation circuit and a comparison circuit, a PWM control means 12a for controlling the IPM of the inverter circuit 4, a waveform storage means 12b for outputting the output voltage of the inverter circuit 4 to a desired waveform, a rotor The electrical angle control means 12c for calculating the electrical angle from the output signal of the position detection means 5a and the output signal of the carrier signal generation circuit, and the waveform storage means 12b from the electrical angle control means 12c in synchronization with the output signal of the carrier signal generation circuit. An inverter circuit 4 based on the output level conversion circuit 12d that calls the signal and outputs the signal to the PWM control means 12a, the current signal corresponding to the motor current detected by the current detection circuit 15, and the rotation speed signal detected by the rotor position detection means 5a. Current control means 12e for controlling the output current and motor applied voltage phase, and the motor current during braking Is constituted by a brake setting means 12f for controlling the voltage applied to the motor phase.
[0018]
The control means 12 is configured as shown in FIG. 2, and the PWM control means 12a is
A sawtooth wave is generated by the rear signal generation circuit 120a, the signal vc is applied to the input terminal of the comparison circuit 121a, and the signal vu of the voltage setting means 122a is applied to the other input terminal of the comparison circuit 121a. The carrier signal generation circuit 120a has a period of 64 μs when the carrier frequency is set to 15.6 kHz, and generates a sawtooth wave whose signal level changes in proportion to time. The sawtooth wave has a higher PWM resolution and is superior to the triangular wave. In the case of a sawtooth wave, there is a drawback that the Nth harmonic of the carrier frequency increases as compared with the triangular wave. However, if the carrier frequency is set to an ultrasonic frequency, the Nth harmonic of the carrier frequency is reduced to noise. This problem disappears because it has no effect.
[0019]
The comparison circuit 121a is a digital comparator in the microcomputer, and generates a PWM waveform by comparing the data of the voltage setting means 122a constituted by a double buffer with a sawtooth carrier signal. The PWM control means 12a shown in FIG. 2 has one phase for three-phase output, and has three similar circuits in the case of three-phase output. However, one carrier signal generation circuit 120a can be shared.
[0020]
The waveform storage means 12b stores a desired voltage signal (sine wave data) corresponding to the electrical angle, and is an array of 256 (8 bits) to 512 (9 bits) numerical data. Numerical data corresponding to the voltage amplitude is 9-bit data, and usually sine wave data corresponding to an electrical angle from −256 to +256 is stored. This numerical data is so-called normalized data, and the way to hold the data is not particularly determined. Therefore, a numerical array in which the execution speed of the program is as fast as possible is desirable.
[0021]
The electrical angle detection unit 12c sets the phase angle φ from the rotation period detection unit 120c that detects the output signal of the rotor position detection unit 5a and detects the rotation period, and the output signal H1 of the reference rotor position detection unit 5a. The number k of output pulses of the carrier signal generation circuit 120a is counted within a period corresponding to the electrical angle of 60 degrees detected by the phase setting means 121c and the rotation cycle detection means 120c, and the electrical angle Δθ of one cycle of the carrier signal is calculated. The electric angle calculating means 122c for calculating the electric angle corresponding to the rotor position, the rotor electric angle calculated by the electric angle calculating means 122c, and the electric angle setting means 123c for setting the applied voltage electric angle by the phase setting means 121c. .
[0022]
The output level conversion circuit 12d is a calling unit 120d for calling the amplitude signal A corresponding to the electrical angle from the waveform storage unit 12b, and a voltage to be output to the PWM control unit 12a by calculating the modulation degree G from the output signal A of the calling unit 120d. It is comprised with the calculating means 121d. Normally, the data in the waveform storage means 12b is a numerical value corresponding to the maximum output level of the inverter circuit 4, so that the voltage calculating means 121d is an operation that reduces the inverter output voltage level, and the modulation degree G is a numerical value smaller than 1. . Usually, the modulation degree G in the sine wave PWM control is called a percentage (%).
[0023]
The phase angle φ and the modulation degree G are output from the current control unit 12e. The current control unit 12e includes an A / D conversion circuit 120e that performs A / D conversion on the output signal of the current detection circuit 15, and an A / D conversion circuit 120e. The current comparison circuit 122e that compares the output signal with the output signal of the current setting means 121e, the modulation degree control means 123e that controls the modulation degree according to the compared error signal, and the modulation degree by the output signal of the modulation degree control means 123e G or phase / current control means 124e for controlling the phase φ.
[0024]
Furthermore, a rotation speed detection means 125e for detecting the rotation speed by detecting the reference signal H1 of the rotor position detection means 5a and a modulation degree change means 126e for changing the modulation degree by the rotation speed signal are provided, and the output of the modulation degree change means 126e. A signal is added to the modulation degree control means 123e so that the modulation degree can be controlled according to the number of rotations.
[0025]
The braking setting means 12f controls the setting of the inverter circuit output voltage and its phase during braking. The braking setting means 12f advances the inverter circuit output voltage phase from an advance angle of 90 degrees to an advance angle of 180 degrees from the motor induced voltage phase according to the braking command. A reverse torque, that is, a braking torque is generated by adding a reverse phase of the voltage.
[0026]
In the above configuration, the waveform relationship of each part corresponding to the electrical angle is as shown in FIGS.
[0027]
FIG. 3 shows the waveform relationship of each part during motor rotation driving before braking. In FIG. 3, Ec is a motor induced voltage waveform, and rotor position signals H1, H2, and H3 of the rotor position detecting means 5a are electrical angles. If the signal changes every 60 degrees and the timing at which the reference signal H1 changes from low to high is 0 degrees, the motor induced voltage Ec has a phase delayed by 30 electrical degrees. The state data of the rotor position signals H1, H2, and H3 are read in synchronization with changes in the rotor position signals H1, H2, and H3, and the rotor electrical angle can be detected every 60 degrees from the state data.
[0028]
The signal vc is a sawtooth wave output signal of the carrier signal generation circuit 120a, and is a timer value of the timer counter that changes from 0 to 512. When the timer value reaches 512, the timer counter overflows and returns to 0 to generate the carrier interrupt signal c.
[0029]
The signal vu is one input signal of the comparison circuit 121a and is basically the same as the output signal of the output level conversion circuit 12d. In this case, the phase angle φ is 0 degree and the modulation degree G is 100%. Indicates. This signal vu is obtained by multiplying the amplitude signal A (−256 to +256) of the sine wave data stored in the waveform storage means 12b by the modulation degree G and adding 256, and is calculated from vu = A × G + 256. It changes in a sinusoidal form from 0 to 512 with 256 as the center value.
[0030]
The signal u indicates a PWM waveform that is compared in magnitude with the signal vu and the output data vc of the carrier signal generation circuit 120a. By driving the inverter circuit 4 via the inverter drive circuit 13 by this signal u and applying a voltage to the motor 5, the motor 5 can be driven with a substantially sinusoidal current, and the noise generated from the motor 5; Vibration can be reduced.
[0031]
The signal u is a drive signal for the U-phase upper arm transistor, and the drive signal for the lower arm transistor is an inverted signal of the signal u. The signal actually applied to the transistor is further subjected to dead time control considering the turn-off time, and has a period for prohibiting simultaneous conduction of the upper and lower arm transistors.
[0032]
As a result, the rotor position electrical angle can be detected by calculation in synchronization with the carrier signal, and the sine wave data stored in the waveform storage means 12b can be read out. The motor current can be increased substantially, and a substantially sinusoidal motor current can be flown, the rotational speed control performance of the motor 5 can be improved, and motor noise can be reduced.
[0033]
FIG. 4 shows a waveform relationship of each part during braking operation, and shows a waveform obtained by advancing the inverter output voltage phase by approximately 180 degrees from the induced voltage phase. Here, the inverter output voltage Vu phase is opposite to the U-phase motor induced voltage waveform Ec. The U-phase current Iu waveform is a waveform advanced by 120 degrees with respect to the induced voltage waveform Ec.
[0034]
At this time, the control phase angle φ is approximately 150 degrees advance, the modulation degree G is a waveform of 40%, and one input signal vu of the comparison circuit 121a is sine wave data A × 0.4, which is from −102 to +102. It changes like a sine wave. When the control phase angle φ is advanced by nearly 60 degrees from the motor induced voltage phase
The inverter circuit output voltage phase is advanced by approximately 90 degrees, and the motor torque decreases. In normal motor drive, when the control phase angle φ is advanced from the motor induced voltage phase, so-called field weakening control is performed, the motor current increases and the torque increases. However, when the control phase φ is rapidly advanced to 90 degrees, the motor current is The torque becomes almost zero without increasing.
[0035]
The motor output P is generally P = Ec × I × cos α, where Ec is the induced voltage, I is the motor phase current, and α is the phase of the induced voltage Ec and the phase current, and the motor angle P is 90 degrees. The output P and the motor torque are zero.
[0036]
Further, when the phase φ is advanced to 150 degrees, the motor applied voltage phase is approximately 180 degrees advanced from the motor induced voltage phase, the phase α is 120 degrees, cos α = −0.5, and negative power, that is, It becomes a power generation brake.
[0037]
Next, FIG. 5 is a flowchart of the brake control program in the braking operation, and the operation in the brake stroke will be described with reference to FIG.
[0038]
Brake control is started from step 200 in FIG. 5. In step 201, the presence / absence of the carrier signal interrupt c is determined. When the carrier signal interrupt c is generated, the process proceeds to step 202 to execute the carrier signal interrupt subroutine. The priority of the carrier signal interrupt is the highest priority except for the abnormal interrupt.
[0039]
The details of the carrier signal interrupt subroutine will be described with reference to FIG. 7. In brief, the rotor position electrical angle is detected by counting the carrier signal, and the sine wave data is received from the waveform storage means 12b according to the electrical angle. Call and set PWM control data. Execution and return of this subroutine requires processing within a few μsec to a few ten μsec.
[0040]
Next, the process proceeds to step 203, where the drive control of the IGBT constituting the inverter circuit 4 is performed. The voltage setting means 122a of the PWM control circuit 12a has a double buffer structure, and the signal actually output after the PWM value is changed is the timing of the next carrier signal.
[0041]
Step 204 detects a change in the rotor position signal. The edge signal of the rotor position signals H1, H2, and H3 is detected to detect whether an interrupt signal has been generated. When an interrupt signal is generated, the process proceeds to step 205. The position signal interrupt subroutine is executed. The priority of the position signal interrupt is set next to the carrier signal interrupt.
[0042]
The details of the position signal interrupt subroutine 205 will be described with reference to FIG. 6. Briefly, detection of the rotor rotation period and the number of rotations, setting of electrical angles every 60 degrees such as 0 degrees, 60 degrees, 120 degrees, Processing such as calculation of the electrical angle of one cycle of the carrier signal is executed.
[0043]
The position signal interrupt subroutine 205 needs to be processed at high speed as in the case of the carrier signal interrupt subroutine, and needs to be processed within a few μsec to a few ten μsec. This is because even if two interrupts overlap at the same time, if the processing is not performed within 50% of one carrier signal period (64 μs), the main routine cannot be executed, and the execution of the program may be hindered.
[0044]
Next, in step 206, the advance angle phase φ from the rotor position reference signal H1 is incremented by Δφ. Normally, in the dehydration operation, the initial phase φ0 is set to 0 degree, and the phase from the induced voltage Ec is advanced by 30 degrees. Δφ may be about 5 degrees or 10 degrees. Δφ is large
If the phase is changed rapidly, the inverter DC voltage rises excessively, and noise is generated in the motor due to a sudden current change. However, if the value is too small, the time for advancing the phase to 90 degrees or longer becomes longer, and the current increases on the way to increase the motor torque. Therefore, it is desirable to change the time in about 0.5 to 1 second. .
[0045]
Next, the routine proceeds to step 207, where it is determined whether or not the phase φ has advanced 60 degrees. When the phase φ is 60 degrees, the motor torque is almost zero because the lead angle is advanced 90 degrees with respect to the induced voltage. Set the value according to the induced voltage. For example, a table showing the relationship between the rotational speed N and the modulation degree as shown in FIG. 9 is stored in the ROM of the microcomputer, and the modulation degree G is set by a lookup table. Since the process of step 208 is only once, when the process is completed, a flag is set so that it will not be executed next time.
[0046]
When the braking operation is performed from the dehydrating high-speed rotation, the motor voltage is set so that approximately half of the induced voltage is applied to each phase, and the modulation degree is set to about 50%, for example. These values are previously obtained from experimental values and stored in a lookup table. If the degree of modulation is reduced, the inverter circuit DC voltage rises due to voltage regeneration, so setting it to about half of the induced voltage is advantageous because there is no voltage regeneration and the braking torque increases.
[0047]
When braking from dehydrating low speed rotation, there is almost no voltage regeneration, so the voltage applied to the inverter circuit can be higher than the motor induced voltage. However, as will be described in detail later, the motor current increases, so the degree of modulation G is several. It is good to set to 10%.
[0048]
Next, the process proceeds to step 209 to determine whether or not the phase φ has advanced to 150 degrees. If it is determined that the phase voltage has advanced 180 degrees from the induced voltage, the process proceeds to step 210 and the phase φ is fixed at 150 degrees and 180 degrees from the induced voltage phase. Holds the advanced voltage phase. Also at this time, voltage regeneration may occur if the phase change is fast, so the control time from the advance angle of 90 degrees to the advance angle of 180 degrees may be set to about 1 second.
[0049]
Next, the process proceeds to step 211 where the current I corresponding to the motor current is detected, and then the process proceeds to step 212 to determine the magnitude of the current I. If the current I is larger than the set current Is, the routine proceeds to step 213, where the modulation degree G is decreased by ΔG. Conversely, if the current I is smaller than the set current Is, the routine proceeds to step 214, where the modulation degree G is increased by ΔG. Next, the routine proceeds to step 215, where it is determined whether the rotational speed N has become zero. When the rotation has stopped, the routine proceeds to step 216, where the IGBT is turned off and the brake control program ends, and the rotation does not stop. Will return to the beginning.
[0050]
Next, an output signal of the rotor position detecting means 5a, that is, a position signal interruption operation when the edges of the rotor position signals H1, H2, and H3 are detected will be described with reference to FIG.
[0051]
In step 300, an external interrupt is generated by an edge signal, and a position signal interrupt subroutine is started. In step 301, status data of rotor position signals H1, H2, and H3 is input, and the rotor position is detected. In step 302, the rotor electrical angle θc is set from the rotor position signal. If the U phase has an electrical angle of 0 degrees, the V phase is set to 120 degrees and the W phase is set to 240 degrees.
[0052]
Next, the process proceeds to step 303, where the count value k of the number of pulses of the carrier interrupt signal c of the carrier signal generation circuit 120a is stored in the carrier counter memory kc, and the process proceeds to step 304 where the count value k is cleared and the process proceeds to step 305. Then, the electrical angle Δθ of one cycle of the output signal of the carrier signal generation circuit 120a is calculated. Since the position signal interruption cycle corresponds to an electrical angle of 60 degrees, Δθ = 60 / kc. 360 degrees is the resolution of 8 bits (256)
Then, it is expressed as Δθ = 42 / kc. Usually, the control performance improves as the resolution is increased, so the value is set to about 360.
[0053]
Here, by calculating the electrical angle per cycle of the carrier signal generation circuit 120a, the electrical angle can be calculated and detected even if the rotation cycle changes, and the rotor position detection accuracy can be improved. A desired voltage waveform corresponding to the electrical angle of the rotor can be applied.
[0054]
Since the frequency of the carrier signal is set to an ultrasonic frequency of 15 kHz or more, the count value kc can secure a resolution of at least 10 or more even at the motor rotation speed during the dehydration operation, and can secure a resolution of 60 or more for one electrical angle. If the instruction execution speed of the microcomputer is sufficient, when the carrier frequency is set to 15.6 kHz and the 8-pole motor is driven at 900 r / min, a resolution of 245 can be ensured, and the voltage waveform is almost sinusoidal even during dehydration rotation. It can be driven with.
[0055]
Next, the routine proceeds to step 306, where it is determined whether or not the reference electrical angle is 0 degree, that is, whether or not the rotor position signal H1 has changed from low to high. If Y, the routine proceeds to step 307 and the period measurement timer counter T is measured. The value is stored in the period measurement memory To, and the routine proceeds to step 308 where the timer counter T is cleared. Thereafter, the routine proceeds to step 309, where the rotor rotational speed N is obtained from the cycle To.
[0056]
The period measurement timer counter increases the clock frequency to 1 to 10 μs in order to improve the measurement accuracy, and counts a signal obtained by dividing the reference clock of the microcomputer with a hard timer.
[0057]
Next, the process proceeds to step 310 to start the count of the timer counter that measures the period To, and the process proceeds to step 311 to return the subroutine.
[0058]
Next, the carrier signal interrupt operation will be described with reference to FIG. FIG. 7 is a flowchart of the carrier signal interrupt subroutine, in which the electrical angle corresponding to the rotor position is obtained in synchronization with the carrier signal, the signal of the waveform storage means 12b is read and PWM output is performed. When the timer counter of the carrier signal generation circuit 120a overflows, an interrupt signal is generated, and a carrier signal interrupt subroutine starting from step 400 is executed.
[0059]
In step 401, the count value k of the carrier counter is incremented, and then, in step 402, the inverter circuit output electrical angle θ is calculated.
[0060]
The electrical angle θ is obtained from the product of the electrical angle Δθ of one carrier signal cycle and the count value k of the carrier counter, and the sum of the phase φ and the electrical angle θc detected by the position signal interruption subroutine. The calculated value of Δθ × k + θc means the rotor position electrical angle, and the phase φ indicates the voltage phase applied to the motor. The electrical angle θ is obtained for each of the U, V, and W phases.
[0061]
In step 403, waveform data corresponding to the electrical angle θ is called from the waveform storage unit 12b. If it is sine wave data, the called data is sin θ. However, the amplitude data is a value of −256 to +256. Since the electrical angle maximum value is 360 degrees, when θ reaches 360 degrees or more, the value returns to 0 and data is read.
[0062]
Next, the process proceeds to step 404, the signal vu is calculated from the modulation degree G obtained in the position signal interrupt subroutine, and the process proceeds to step 405, where the output setting buffer of the comparison circuit 121a for applying the signal to the PWM control circuit 12a, ie, output setting means. The data is transferred to 122, and the process proceeds to step 406 where the subroutine returns. The V-phase and W-phase are processed in the same manner as the U-phase from step 402 to step 405.
[0063]
The processing in the carrier signal interrupt subroutine needs to be completed within one carrier signal cycle. If the carrier frequency is 15.6 kHz, it is necessary to finish the process within 30 μs at the latest. In the case of a program step in which the process does not finish within 30 μs, the program is divided, and the carrier interrupt is first in the U phase and second. You may make it perform the process of W phase in V phase and the 3rd time.
[0064]
FIG. 8 shows a vector diagram of one phase of the inverter circuit output voltage (motor applied voltage) Va, motor induced voltage Ec, and motor current I as viewed from the motor neutral point during braking operation. In the case of a sine wave, the inverter output voltage Va is equal to the sum of the voltage drop of the motor coil resistance R and the inductance L and the motor induced voltage Ec, and is expressed by Va = Ec + I × (R + jωL). Here, ω is 2πf, and the inverter output frequency f is expressed by f = p × N ÷ 120. Here, p is the number of poles, and N is the number of rotations [r / min].
[0065]
Since the phase φ at the initial stage of the brake is set to an advance angle of 60 degrees and the modulation degree G is set to 50% in the case of the high speed rotation speed, the vector diagram of FIG. Since the phase of the motor induced voltage Ec is delayed by 30 degrees from the reference phase of the rotor position signal H1, the phase of the motor applied voltage Va is approximately 90 degrees advanced from the induced voltage Ec. As shown in this figure, since the phase of the motor current I is approximately 90 degrees ahead of the induced voltage phase, the motor output is almost zero and almost no motor torque is generated.
[0066]
FIG. 8B is a vector diagram when the motor rotation speed is high-speed rotation, and a vector diagram in which the phase of the inverter circuit output voltage Va is further advanced by 90 degrees and the phase of the induced voltage Ec is advanced by 180 degrees. Show. At this time, since the rotation speed is high and the frequency f is high, the voltage drop (I × jωL) corresponding to the motor inductance is large, and the voltage drop corresponding to the resistance is small.
[0067]
The motor output P is proportional to a value obtained by multiplying the product of the induced voltage Ec and the motor current I by cos α, and the current phase α is advanced by about 120 degrees, so that a negative motor output, that is, power generation energy is generated. This generated energy is consumed by the motor coil resistance and is not regenerated to the inverter DC power supply side. From this vector diagram, the power consumed by the motor coil (I × I × R) is the motor power generation energy (Ec × I × cos α) and the energy supplied from the inverter circuit side (Va × I × cos (180−α)). Since it becomes a sum, it can be seen that the generated energy is consumed by resistance.
[0068]
The induced voltage Ec during high-speed rotation is considerably higher than the motor applied voltage Va. At this time, sufficient braking torque is generated even if the inverter output voltage Va is set to about half of the motor induced voltage Ec and the motor current is reduced. To do.
[0069]
FIG. 8C is a vector diagram when the motor rotation speed is low. When the rotation speed decreases, the motor induced voltage Ec decreases and the voltage drop (I × jωL) due to the coil inductance also decreases. Since the voltage drop corresponding to the resistance increases, the current phase α further advances and approaches 180 degrees.
[0070]
Further, since the impedance (R + jωL) of the coil decreases, the motor current I increases, and the motor braking torque (negative torque) does not decrease so much. However, if the rotational speed further decreases, the reactance decreases and the current increases, so the modulation degree G is controlled according to the current value as shown in the flowchart of FIG.
[0071]
Contrary to FIG. 8 (a), when the initial phase is set at a retard angle of 60 degrees or a retard angle of 90 degrees, the inverter circuit DC voltage rises due to regenerative energy. If the phase is shifted by 180 degrees from the retarded direction, the current vector does not become as shown in FIG. 8, so the generated energy returns to the inverter side and the DC voltage rises. Therefore, the withstand voltage of the rectifier circuit capacitor and power semiconductor is increased. There is a need.
[0072]
(Example 2)
The control means 12 shown in FIG. 1 controls the inverter circuit output voltage in accordance with the rotational speed to control the motor current. Other configurations are the same as those of the first embodiment.
[0073]
The operation in the brake stroke in the above configuration will be described with reference to FIG. Note that the flowchart of FIG. 10 is a modification of the brake control subroutine shown in FIG. 5 of the first embodiment, and only the additional change portion will be described.
[0074]
The brake control program starts from step 500, and the processing from step 201 to step 210 is the same as in FIG. In step 210, the phase φ is fixed to 150 degrees, and then the process proceeds to step 208 ′. In step 208 ′, the modulation degree G is set according to the rotational speed N.
[0075]
As shown in FIG. 9, the relationship between the rotational speed N and the modulation degree G is such that when the rotational speed N decreases, the modulation degree G also decreases, and the motor current value becomes substantially constant or becomes a value that does not exceed the rated current of the IGBT. The relationship between the number N and the modulation degree G is obtained experimentally, stored in the memory of the microcomputer, and the modulation degree G is controlled by a lookup table. Such a look-up table method is characterized by a simple program and improved reliability.
[0076]
Steps other than step 208 ′ are the same as those in FIG.
[0077]
In addition to the relational expression between the rotational speed N and the modulation degree G as described above, or the lookup table method, a combination of the current feedback method and the lookup table method described in the first embodiment is also conceivable. That is, the normal control may be a method in which the modulation degree G is decreased only when the motor current increases from the set value by controlling with the look-up table of the rotation speed N and the modulation degree G.
[0078]
As described above, the feature of the present invention is that the motor power generation energy is consumed by the motor coil resistance by advancing the inverter circuit output voltage phase by approximately 90 degrees from the motor induced voltage phase to 180 degrees when braking is started. The inverter circuit DC voltage can be prevented from increasing, the voltage of the inverter circuit parts can be lowered, the reliability is improved, and no special parts are required, so that an inexpensive braking device can be realized.
[0079]
In addition, braking torque can be generated with a small motor current by applying a voltage that is approximately half of the induced voltage during high-speed rotation, and an increase in motor current can be prevented by reducing the inverter output voltage during low-speed rotation. Heat generation can be reduced and braking torque can be increased.
[0080]
Further, it is obvious that the present invention can be applied not only to dehydration braking of a washing machine but also to a washing pump of a vacuum cleaner or a dishwasher, a servo motor, or the like.
[0081]
【The invention's effect】
As described above, according to the first aspect of the present invention, an AC power source, a rectifier circuit connected to the AC power source, an inverter circuit that converts DC power of the rectifier circuit into AC power, and the A motor driven by an inverter circuit, and the motor Made of permanent magnets Rotor of Rotor position detecting means for detecting the position, and control means for controlling the inverter circuit, wherein the control means is configured to set the inverter circuit output voltage phase to be higher than the induced voltage phase of the motor. Around 90 degrees Advance Further, the inverter circuit output voltage phase is advanced to around 180 degrees. Therefore, the braking torque can be generated in the motor with a small amount of current without regenerating the induced voltage of the motor to the DC power supply side, the temperature rise of the motor and the power semiconductor, and the power semiconductor. Can prevent voltage rise.
[0082]
Claims 2 According to the invention described in the above, the control means brakes the inverter circuit so that the inverter circuit output voltage is larger than the motor induced voltage at the time of low-speed rotation of the motor. Since the braking torque is generated by flowing the braking force, it is possible to prevent the braking torque from being lowered during low-speed rotation.
[0083]
Claims 3 According to the invention described in the above, the control means continuously advances the inverter circuit output voltage phase from the initial phase to the vicinity of 180 degrees to maintain the phase. When the voltage is changed, an excessive voltage rise of the inverter circuit and abnormal motor noise can be prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram of a motor driving apparatus according to a first embodiment of the present invention.
FIG. 2 is a block diagram of control means of the motor drive device
FIG. 3 is a time chart for normal driving of the motor driving device.
FIG. 4 is a time chart during braking of the motor drive device.
FIG. 5 is a flowchart of a brake control program for the motor drive device.
FIG. 6 is a flowchart of a position signal interrupt subroutine of the motor drive device.
FIG. 7 is a flowchart of a carrier signal interrupt subroutine of the motor driving apparatus.
FIG. 8A is a vector diagram during braking operation of the motor drive device.
(B) Vector diagram at the time of high speed rotation of the motor drive device
(C) Vector diagram of the motor drive device during low speed rotation
FIG. 9 is a relationship diagram of motor rotation speed and sine wave PWM control modulation degree during braking operation of the washing machine.
FIG. 10 is a flowchart of a brake control program for a motor drive device according to a second embodiment of the present invention.
[Explanation of symbols]
1 AC power supply
3 Rectifier circuit
4 Inverter circuit
5 Motor
5a Rotor position detection means
12 Control means

Claims (3)

An AC power source, a rectifier circuit connected to the AC power source, an inverter circuit for converting DC power of the rectifier circuit into AC power, a motor driven by the inverter circuit, the rotor consisting of permanent magnets of the motor Rotor position detection means for detecting the position, and control means for controlling the inverter circuit, the control means advance the inverter circuit output voltage phase closer to 90 degrees than the induced voltage phase of the motor , Further, the motor drive apparatus is configured to generate a braking torque by advancing the inverter circuit output voltage phase to around 180 degrees .   2. The motor driving apparatus according to claim 1, wherein the control means brakes the inverter circuit so that the inverter circuit output voltage is higher than the motor induced voltage during low-speed rotation of the motor.   2. The motor driving apparatus according to claim 1, wherein the control means continuously advances the inverter circuit output voltage phase from the initial phase to around 180 degrees to maintain the phase.

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