JPH04156297A - Motor control means - Google Patents

Abstract

PURPOSE:To enhance the start voltage of a motor by providing a motor with a start control means that outputs a start signal to a frequency setting means so that the frequency setting means can output a setting signal for increasing a carrier frequency when starting the motor. CONSTITUTION:Switching elements Tr11-Tr32 of inverter 33 are turned on and off by an inverter control means 5 to carry out pulse width modulation of direct current, thereby supplying a motor 4 with a predetermined AC power. Further, the inverter control means 5, based on a setting signal from a frequency setting means 7, determines a carrier frequency for the pulse width modulation. Furthermore, when receiving a start signal from a start control means 6, the inverter control means 5 causes the frequency setting means 7 to output a setting signal to enhance the carrier frequency, and when a predetermined period of time passes, the frequency setting means outputs a setting signal for normal low carrier frequency. With this setting signal, the inverter 33 carries out pulse width modulation of direct current using a high carrier frequency for a predetermined period of time for starting the compressor, thereby causing the starting torque of the motor 4 to be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a motor control device that controls a compressor motor, etc., and particularly relates to starting control of an inverter.

(Prior Art) Conventionally, some control devices for compressor motors in air conditioners are equipped with an inverter, as disclosed in Japanese Patent Publication No. 60-54571. This motor control device consists of a forward converter, a chopper, an inverter, and a compressor motor connected in order to a power source.The forward converter converts the AC voltage from the power source into a DC voltage, and the chopper converts the AC voltage to DC voltage. , the AC voltage is converted to AC voltage by an inverter, and the AC voltage is applied to the motor.

Then, the DC voltage is controlled by a speed command signal based on the indoor temperature, etc., and the inverter control circuit controls each transistor of the inverter on/off based on the DC voltage to control the rotational speed of the motor.

(Problem to be Solved by the Invention) In the above-mentioned motor control device, the output voltage and output current of the chopper section are detected, and the output voltage and output frequency of the inverter are controlled so that the operating torque of the motor is equal to or less than a predetermined value. are doing.

On the other hand, in an air conditioner, if the motor is controlled by an inverter, the starting torque is not very large, so once the compressor is stopped, the compressor is put on standby until the differential pressure between the discharge side and the suction side is balanced. ing. Also,
In order to balance the differential pressure between high and low levels, a pressure equalization circuit is provided in the refrigerant circuit, and a pressure equalization valve is opened when the compressor stops.

However, this has the problem that it takes a long time (for example, several minutes) to restart the compressor, resulting in a lack of comfort. Further, it is necessary to provide a pressure equalization circuit, etc., which increases the number of parts and creates a complicated refrigerant circuit configuration.

The present invention has been made in view of the above, and aims to increase the starting torque of the motor and shorten the standby time of the compressor.

(Means for Solving the Problems) In order to achieve the above object, the means taken by the present invention are as follows:
The carrier frequency is increased only when the motor is started.

Specifically, as shown in FIG.
) and motor (4) are connected in order, and the power converter (
3) includes a plurality of switching elements (Trn) to (Tr
32) is assumed to be a motor control device equipped with an inverter (33).

Then, the switching elements (Trn) to (Tr32) of the inverter (33) are turned on and off to perform pulse width modulation of the DC, and the inverter (33) is provided. Furthermore, frequency setting means (7) is provided for outputting a carrier frequency setting signal to the inverter control means (5) so that the carrier frequency for pulse width modulation in the inverter (33) is increased or decreased. In addition, the above motor (4)
A starting signal is output to the frequency setting means (7) so that the frequency setting means (7) outputs a setting signal for increasing the carrier frequency of the inverter control means (5) within a predetermined time when starting the inverter. The configuration includes a control means (6).

Further, the means taken by the invention according to claim (2) is that in the invention according to claim (1), the motor (4) is constituted by a compressor motor provided in the compressor of the air conditioner, The control means (6) is configured to output a starting signal when starting the compressor.

(Function) With the above configuration, in the invention according to claim (1), the power supplied from the power source (2) is converted into control power by the power converter (3), and in particular, the power is controlled by the inverter (33). is converted into AC power, and the motor (4)
Specifically, in the invention according to claim (2), the air is supplied to the motor (4) of the compressor in the air conditioner, and the motor (4) is driven.

Then, the switching element (
Tr.sub.n) to (Tr.sub.32) are turned on and off by the inverter control means (5), and pulse width modulate the direct current to supply predetermined alternating current power to the motor (4). Furthermore, the inverter control means (5) includes frequency setting means (
The carrier frequency of pulse width modulation is determined based on the setting signal of 7), and this frequency setting means (7) is the starting signal of the starting control means (6), specifically, in the invention according to claim (2). , upon receiving a compressor starting signal, outputs a setting signal to increase the carrier frequency, and after a predetermined time elapses, outputs a normal setting signal for a low carrier frequency.

Based on this setting signal, the inverter (33) pulse-width modulates the DC with a high carrier frequency for a predetermined period of time only when the compressor is started, and the torque of the motor (4) at the time of starting is increased.

(Effect of the invention) Therefore, according to the invention according to claim (1), since the carrier frequency for the pulse width modulation can be increased, the starting torque when controlling the motor (4) by an inverter is reduced. Since it can be made larger, the motor (4)
The starting control range of the motor (4) can be expanded, and the range of use of the motor (4) can be expanded.

In addition, since the carrier frequency is increased only when the motor (4) is started, the switching elements (Trll) to (Tr
There is no need to consider the heat generated by the motor (4).
), there is no need to consider resonance, and the starting torque can be increased with a simple configuration.

Further, according to the invention according to claim '2J, since the compressor can be started in a state where the pressure difference between high and low levels is large, the waiting time for restarting the compressor can be shortened.
The comfort of air conditioning can be improved. Furthermore, since a pressure equalizing circuit for equalizing the pressure difference between high and low levels can be omitted, the number of parts can be reduced and the refrigerant circuit configuration can be simplified.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

As shown in FIG. 2, (1) is a motor control device, which connects a three-phase power source (2) to a power converter (3) and a motor (4).
are connected in sequence to drive and control the motor (4). Although this motor (4) is not shown, it is a motor for a compressor installed in an air conditioner, and the motor (4)
The third motor rotates to drive the compressor and compress the refrigerant.
As shown in the figure, it is composed of an induction motor having three windings (4a) to (4C).

The power converter (3) has a diode type rectifier circuit (3).
1), a smoothing capacitor (32), and a transistor-type inverter (33), the three-phase AC from the three-phase power supply (2) is converted into DC by a rectifier circuit (31), and the smoothing capacitor (32) ), then inverter (33)
converts direct current into alternating current and supplies controlled alternating current power to the motor (4).

As shown in FIG. 3, the inverter (33) includes six free-wheeling diodes (D1+) to (D32) and six switching elements, transistors (Tr n ) to (
Trx). And the above inverter (33
) is an inverter control circuit (
5) is connected, and the inverter control circuit (5) consists of a microcomputer (51) and a pace driver (52), and the microcomputer (51) controls each of the transistors (T
r++) to (Tr32) are turned on and off to perform pulse width modulation of the direct current so that the inverter (33) supplies predetermined alternating current power to the motor (4). An input device (53) for inputting compressor operating signals, capacity signals, etc. is connected to the microcomputer (51), and
An output device (54) indicating the operating status of the compressor is connected.

Therefore, the formation of a PWM (pulse width variation: A) control pattern by the microcomputer (51) will be explained.

To summarize, this PWM control pattern is formed by determining a PWM control pattern so that the locus of time integration of the output voltage approaches a circular locus.

To explain this in detail, first consider the potential of the output terminal of the inverter (33) (va, vt), vc, and the time integral λP of the motor (4).

7・-g・ (va+α2Ilvb tenαI+VC) However, α−exp　−j(2/3)π→　　　　→ λp=jVpdt Now, the three-phase winding (2) of the induction motor (1) has a stratum corneum. voltage vector VP and its time integral when λρ draws a circular locus on the complex plane.

On the other hand, in the voltage source inverter (33), one of the transistors (Trn) to (Tr32) in each phase arm is always in the on state, so for convenience, the on state on the + side is
1'', - side on state is represented by [O, C phase, b phase, C
If the phases are expressed as rlolJ, rollJ, etc. in order, there are eight states of the inverter (33). The voltage vector VP (P-'O~7) in each state is a large x b<-1
'i vd (Pl-~, moves at a speed of 7i7i V d (however, it stops in the case of zero vector).

From the above, the PWM control pattern of the voltage source inverter (33) is determined by appropriately selecting the time integral λP of the voltage vector. (The designated radius R is R-V, /ω, where Vl is the effective value of the line voltage of the fundamental voltage and ω is the angular frequency.

” 6 and a zero vector (for example ■○), stay at point PO for time τ0 (this state is indicated by symbol 0), then take V4 for time τ4 to reach point q1, and further V6 for time τ6. Consider the case where point P1 is reached by taking only In this case, in △pOq, pI, PoP, = V, -r
.

POQ+-mu/3 Vd・rs ql p, -A million Vd・τ6 V6. Time to take VO τ4. τ6. τ0 is obtained.

τ4 ノ To −ks −5in(π/3− φ
0 ) r6/ To -ks S4n φOro/
To =1-ks-8jn(φo+yr/3)...
...(3) where ks is the voltage control rate, k, 5--ITV+/Vd.

Equation (3) above is a relational expression in the range where the angle φ is 0≦φ≦π/3, but in other sections, since the inverter (3)) performs symmetrical three-phase operation, the following By replacing each symbol as shown in Table 1, a relational expression in the range of 0≦φ≦2π can be obtained.

Next, the on/off pattern (PWM control pattern) of each transistor (Trn) to (Tr32) is determined based on the time τ of the voltage vector in equation (3) above.

In this case, the relationship between the voltage vector time τ and the PWM control pattern changes depending on the order in which the voltage vectors are taken.

Now, by repeating the same pattern and adding the constraint that the transistor is switched 0N10FF only once in each period TQ, the PWM control pattern is as shown in Figure 6 (a).
The four patterns shown in (d) are representative (in the figure, τ indicates the on time of the transistor on the + side, and τ- indicates the on time of the transistor on the one side).

In this embodiment, the PWM control pattern shown in FIG. In the voltage source inverter (33), PWM
The control pattern is uniquely determined by knowing the name of the transistor that turns on at the beginning of the period To and the time at which it turns off, so with reference to the above equation (3) and FIG. 6 (a), The PWM control pattern is determined by the following formula when the angle φ is in the range O≦φ≦π/3.

ra, −/To −1−J2 ・(V+ /Vd)・
5in (φ0+π/3) r b −/To −1−J2 ・(V+ /Vd)
・Sinφ0re−/To−1 (always ON) ・・・・・・(4) The relational expression (4) of the PWM control pattern in the range of O≦φ≦π/3 is expressed by each symbol in the same way as above. 0 if you replace
The relational expression is within the range of ≦φ≦2π.

The microcomputer (51) then operates each transistor (Tr) based on the formula
n) to (Tr32) are calculated, and the motor (4)
is under control.

Further, as a feature of the present invention, a start control circuit (6) which is a compressor start control means is connected to the microcomputer (51) via a frequency setting circuit (7) which is a frequency setting means. The starting control circuit (6) outputs a starting signal when starting the compressor, and the frequency setting circuit (6) outputs a starting signal when starting the compressor.
7) outputs a carrier frequency setting signal to the microcomputer (51) so that the carrier frequency increases or decreases. The frequency setting circuit (7) includes a starting control circuit (6).
), when a starting signal is input from
The device is configured to output an increase setting signal so that the carrier frequency becomes high during a predetermined period of time (seconds), and output a decrease setting signal so that the carrier frequency decreases to a normal frequency after a predetermined period of time has elapsed.

Based on this setting signal, the microcomputer (51) increases the carrier frequency only when starting the compressor, for example, doubles the normal frequency, that is, divides the period To in the above equation (4),
It is configured to increase the number of times each transistor (Tru) to (Tr32) turns on.

In detail, Fig. 7 shows the normal carrier frequency ('-2K
Hz), the output voltage of each phase is shown, and the 8th
The figure shows the output current of the inverter (33), while Figure 9 shows the output voltage of each phase when the carrier frequency is doubled (4KHz), and Figure 10 shows the output of the inverter (33). Comparing Figure 8 and Figure 10, it shows that as the carrier frequency increases,
The output current becomes close to a sine wave.

Next, the relationship between the output current ■ of the inverter (33) and the torque T is T=f(3・P−fs)/(9,8・4・π・r2)lX(V/f)'・・
・■ fs: Slip frequency P: Number of motor poles ``2: Secondary copper loss V: Inverter output voltage f: Inverter output frequency Tcc I'' = 16), °, I (V/f).

Therefore, if the carrier frequency is doubled and the pulse width is made smaller as shown in FIG. 9, the peak value of the effective current value becomes lower as shown in FIG. ) to (Tr32), the higher the number of cuts in the output voltage, that is, the higher the carrier frequency, the larger the current can flow. As a result, the output torque T of the inverter (33) increases according to the above equation (6).

In addition, only the fundamental wave component of the current contributes to the drive torque of the motor (4), and the harmonic component only becomes torque pulsation, and the closer the current waveform is to a sine wave (see Figure 10)
, the torque T increases.

For the reasons mentioned above, the present invention is designed to increase the carrier frequency.

On the other hand, when the carrier frequency is increased, each transistor (Tr++) to (Tr32) turns on and off according to this carrier frequency, so switching loss (heat) occurs, and the transistors (Trll) to (Tr32)
It becomes necessary to significantly strengthen the cooling of the

In addition, the upper and lower arm transistors (Trn) to (Tr3
2) In order to prevent a short circuit, a put time is set in which the off operations of the transistors (Trn) to (Tr32) in the upper and lower arms overlap, and this dead time is the same even if the carrier frequency is increased, so this The accumulated dead time increases, the motor (4) tends to resonate, and stability decreases.

Therefore, in the present invention, the carrier frequency is increased only when the compressor is started, so as not to generate much heat, and since the motor (4) is accelerating,
The stability of 4) is maintained.

Next, the operation of this motor control device (1) will be explained.

First, the three-phase AC is converted into a rectifier circuit (31) from the three-phase current (2).
The rectifier circuit (31) converts the direct current into direct current, and this direct current is smoothed by the smoothing capacitor (32), and then is converted into a predetermined alternating current by the inverter (33), which is then supplied to the motor (4). The motor (4) rotates and drives the compressor.

On the other hand, each transistor (Tr
n) to (Tr 32) are turned on and off by a microcomputer (51), and the microcomputer (51) selects eight types of voltage vectors (Vo=V7) so that the vector locus follows the circumference. , PWM based on the above equation (4)
A control pattern is calculated to control on/off of each transistor (Trn) to (Trz) of the inverter (33).

The microcomputer (51) then carries out the carrier period (To
) for each transistor (Tr ++ ) ~ (Tr x)
The on-time of the carrier frequency (1,
/To).

Therefore, regarding this carrier frequency change control, the 11th
This will be explained based on the diagram.

First, after starting, in step STI, it is determined whether the compressor is being started. In other words, the starting control circuit (6
), the frequency setting circuit (7) outputs a carrier frequency increase setting signal for a predetermined period of time (5 seconds to 10 seconds). When the microcomputer (51) receives this increase setting signal, the microcomputer (51) moves from step STI to step Sr1, doubles the carrier frequency, that is, divides the carrier period To, and each transistor (Tr++ ) to (Tr32) are controlled twice, and the process returns. And this microcomputer (51)
Under the control of each transistor (
Tro) to (Tr32) are turned on and off, and as shown in FIG. 9, the DC is cut into twice the number of cuts with a small pulse width. As a result, the output current of the inverter (33) increases, the output torque T increases (see equation (6) above), and the starting torque of the motor (4) increases.

On the other hand, after a predetermined period of time has passed after the compressor is started, the frequency setting circuit (7) outputs a carrier frequency reduction setting signal, and the microcomputer (51) moves from step STI to step ST3 and changes the carrier frequency to the normal level. The frequency drops and returns.

As a result, each transistor (Tr
n) to (Tr32) perform normal on/off operations, and the motor (4) rotates.

Therefore, by making it possible to increase the carrier frequency for the pulse width modulation, the starting torque when controlling the motor (4) using an inverter can be increased, thereby expanding the starting control range of the motor (4). Therefore, the range of use of the motor (4) can be expanded.

In addition, since the carrier frequency is increased only when the motor (4) is started, the transistors (Trn) to (Tr32)
Furthermore, since the motor (4) is accelerating, there is no need to consider resonance, and the starting torque can be increased with a simple configuration.

Further, since the compressor can be started in a state where the pressure difference between the heights and the low points is large, the waiting time for restarting the compressor can be shortened, and the comfort of air conditioning can be improved. Furthermore, since a pressure equalizing circuit for equalizing the pressure difference between high and low levels can be omitted, the number of parts can be reduced and the refrigerant circuit configuration can be simplified.

In the above embodiment, the microcomputer (51) performs PWM control so that eight voltage vectors follow the circumference, but as shown in FIG. (33) may be subjected to PWM control, in which case the microcomputer (51) increases or decreases the carrier frequency, that is, the frequency of the triangular wave A.

Furthermore, although this embodiment has been described with respect to a motor of a compressor of an air conditioner, the invention of claim (1) is not limited to this motor.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention. 2 to 12 show embodiments of the present invention, FIG. 2 is a circuit block diagram of a motor control device, and FIG. 3 is an electric circuit diagram of an inverter. Fig. 4 is an explanatory diagram showing the state of the inverter using eight voltage vectors, Fig. 5 is an explanatory diagram of voltage vector control, and Fig. 6 is an explanatory diagram showing the type of PWM control pattern at each angle. Fig. 7 is an output voltage waveform diagram of the inverter at low carrier frequency, Fig. 8 is an output current waveform diagram of the inverter, and Fig. 9 is an output voltage waveform diagram of the inverter at high carrier frequency.
FIG. 10 is a diagram of the same output current waveform. FIG. 11 is a control flow diagram showing a change in carrier frequency. FIG. 12 is a control waveform diagram and an inverter output voltage waveform diagram showing another PWM control. (1) Motor control device (2) Power source (3) T1 horn converter (4) Motor (5) Inverter control circuit (6) Start control circuit (7) ... Frequency setting circuit (33) ... Inverter (Trn) - (Trs) ... One transistor (1) ... Motor control device (2), power supply (3) ... Power conversion device ( 4)...Motor (5)...Inverter control circuit (6)...Starting control circuit (7)...Frequency setting circuit (33)...Inverter (Tr++) ~ (Trri...Transistor Figure 2) (' Figure 3 Figure 12/ / Figure 5 Figure 8 Figure 10rI!J

Claims (2)

[Claims] (1) A power source (2), a power converter (3), and a motor (4) are connected in order, and the power converter (3) has a plurality of switching elements (
In a motor control device provided with an inverter (33) including Tr_1_1) to (Tr_3_2), each switching element (Tr_
an inverter control means (5) that controls the inverter (33) so that a predetermined AC power is supplied to the motor (4) by pulse width modulating the DC by turning on and off Tr_1_1) to (Tr_3_2); and a frequency setting means (7) for outputting a carrier frequency setting signal to the inverter control means (5) so that the carrier frequency for pulse width modulation in the inverter (33) is increased or decreased; The frequency setting means (7) sends a setting signal for increasing the carrier frequency of the inverter control means (5) within a predetermined time during startup.
1. A motor control device comprising: a starting control means (6) for outputting a starting signal to the frequency setting means (7) so that the frequency setting means (7) outputs a starting signal. (2) In the motor control device according to claim (1), the motor (4) is constituted by a compressor motor provided in a compressor of an air conditioner, while the start control means (6) A motor control device configured to output a starting signal.