JPS6332039B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pole conversion induction motor speed control system. As a conventional example, JP-A-49-
There is No. 59217 "Speed variable device for AC motor".
However, in the conventional example, speed control by an inverter and speed control by changing the number of poles are simply combined, and the speed control range by the inverter for one number of poles is different from the speed control range by the inverter for another number of poles. As if continuing,
The problem was that the control device for changing the number of poles and the inverter could not be linked to perform smooth switching control, and continuous and smooth operation could not be performed over a wide range from low speed to high speed.

In addition, Fig. 1 and Fig. 2 show examples of other conventional devices, and Fig. 1 shows a pole change induction motor (hereinafter abbreviated as pole change motor) driven by a commercial power source.
FIG. 2 is a block diagram showing the configuration of the control system, and FIG. 2 is a characteristic diagram showing the relationship between speed and time of the control system.

In Fig. 1, a commercial power supply 10 and a pole changing motor 1
A winding switching circuit 14 is provided in the middle of the circuit connecting the windings 2 and 2, and a command circuit 16 that outputs a signal for changing the number of poles is connected to the winding switching circuit 14. A load 20 is interlocked with the pole changing motor 12 via a power transmission mechanism 18 .

The winding switching circuit 14 receives a signal from the command circuit 16 and changes the windings of the pole changing motor 12 using relay contacts, semiconductor elements, etc. to create winding combinations with different numbers of poles. This winding switching circuit 14 has various types and is well known, so its internal configuration will be omitted.

In the configuration of the example in FIG. 1, at time _t1 in FIG. 2, the winding switching circuit 14 receives a signal from the command circuit 16.
is operated to cut off the power from the commercial power supply 10 and change the number of poles of the winding of the pole transformer motor 12 to P=
Change from P ₄ to P=P ₂ . This switching time is several ms
It is as short as ~several 10 ms, and considering the load GD ² ,
During this period, the load speed fluctuation due to the non-excitation state can be almost ignored.

Next, even when decelerating at time t ₂ , time t ₁
This can be achieved by changing the number of poles of the winding of the pole changing motor 12 from P=P ₂ to P=P ₄ in the same way as in the case of .

However, the speed control method shown in the example shown in Figure 1 above is intermittent, and when switching windings, sudden acceleration torque and braking torque are generated, which not only shocks the load, but also has the disadvantage that continuous speed control is not possible. There is.

Figures 3 and 4 show other conventional devices.
Figure 3 shows a general-purpose induction motor (1
FIG. 4 is a block diagram showing the configuration of a control system in the case of variable-speed driving of a motor (having two poles), and FIG. 4 is a characteristic diagram showing the relationship between torque and speed showing the usable rated range of this control system.

In FIG. 3, the same reference numerals as in FIG. 1 indicate the same or corresponding parts. An inverter device (variable voltage variable frequency inverter device) 24 that varies voltage and frequency is provided in a circuit connecting a commercial power source 10 and a general-purpose induction motor 22, and a speed command circuit 26 is connected to the inverter device 24. In the configuration shown in FIG. 3, a command signal is supplied from the speed command circuit 26 to the inverter device 24 to drive the general-purpose induction motor 22 while maintaining the optimum excitation voltage and/or frequency ratio.

FIG. 4 shows the output characteristics (torque range in which the induction motor 22 can drive the load 20) of the example shown in FIG. 3 above. As an example, when driving an induction motor with P=P ₄ , n ₄₁ is the minimum speed, n ₄₄ is the maximum speed, and n ₄₂ is the inflection point speed where the cooling capacity decreases as the speed decreases and the reduced torque region begins. , n ₄₃ is a speed corresponding to around 60 Hz, which is the speed at which the output voltage of the inverter device 24 becomes maximum. At higher speeds than this point, the voltage becomes constant and the constant output characteristic becomes appropriate.

In this way, when driving an induction motor with one pole at variable speed using a voltage and frequency control device such as an inverter or cycloconverter, in the high-speed region, the torque may be reduced due to constant voltage, and the external fan of the induction motor may be There are problems such as the strength of the end ring against centrifugal force, the noise of the fan, an increase in temperature due to a decrease in the cooling effect of the external fan and end ring fan in the low speed range, vibration and torque ripple at low speed rotation, etc. However, the driving range with sufficiently large torque was extremely limited.
Generally it is between 15 or 20Hz to 60Hz.

As described above, the conventional device has problems such as discontinuous speed control when controlling the speed of the pole-changing motor 12 using the commercial power source 10 and shock on the load when changing the number of poles, as well as problems with the inverter device 24.
In the case of variable speed control of the general-purpose induction motor 22, there are problems with the mechanical strength and noise of the rotating parts in the high speed range, a decrease in output torque due to entering a constant output drive, and output torque due to a reduction in cooling effect in the low speed range. There were inconveniences such as a decrease in torque, vibration, torque ripple, and uneven rotation.

The present invention has been made in view of the above-mentioned conventional problem, and its purpose is to drive a pole variable motor with a variable voltage variable frequency inverter device, and to increase the motor speed by changing the first set frequency. Sometimes, the number of poles is changed to create a motor with a smaller number of poles and the command frequency is lowered by the pole number ratio.If the motor speed is to be lowered, the number of poles is changed at the second set frequency to create a motor with a larger number of poles. It is an object of the present invention to provide a speed control device for a pole-change induction motor that eliminates the disadvantages of the conventional device by using a control device that increases the command frequency of the motor by the pole number ratio.

In order to achieve the above object, the present invention provides a pole-changing induction motor, an inverter device that varies voltage and frequency, a winding switching circuit for the pole-changing induction motor, and a winding switching circuit for changing the voltage and/or frequency of the pole-changing induction motor. and a speed command circuit that gives a voltage command, a rise/fall command circuit that commands the speed increase or fall of the pole number changing induction motor, and a frequency signal generator that generates a frequency signal based on the signal from the rise/fall command circuit. a first frequency setting circuit for setting a first frequency, a second frequency setting circuit for setting a second frequency, a set frequency signal from the first frequency setting circuit, and a set frequency signal from the frequency signal generation circuit. a first comparator that compares the frequency signal with the frequency signal; a second comparator that compares the frequency signal from the second frequency setting circuit with the frequency signal from the frequency signal generation circuit; and a frequency signal from the frequency signal generation circuit. A frequency divider/multiplier that divides or doubles the frequency of the signal according to the pole number ratio of the pole number conversion induction motor and supplies a frequency signal to the speed command circuit, and a rise signal from the rise/fall command circuit. and a coincidence signal from the first comparator to operate the frequency divider/multiplier and the winding switching circuit; The present invention is characterized by comprising a second control circuit that operates upon receiving a coincidence signal from a second comparator and operates the frequency divider/multiplier and the winding switching circuit.

Hereinafter, preferred embodiments of the present invention will be described based on the drawings. FIG. 5 is a block diagram showing the configuration of an embodiment of the apparatus of the present invention, in which the same parts as in FIGS. 1 and 3 are given the same reference numerals. In FIG. 5, an inverter device 24 and a winding switching circuit 14 are provided in series in a circuit connecting the commercial power source 10 and the polar transformer motor 12, and a speed command circuit 26 is connected to the inverter device 24,
The speed command circuit 26 and the winding switching circuit 14
In this configuration, a sequence control circuit 28 is connected to.

The above sequence control circuit 28 is configured as follows. A rise/fall command circuit 30 that raises or lowers the command frequency supplies a rise signal A to the first control circuit 32 when the command frequency is rising, and a fall signal B to the second control circuit 34 when the command frequency is falling. When the frequency signal generating circuit 36 receives the signal from the raising/lowering command circuit 30, it generates an analog or digital signal corresponding to the drive frequency of the pole changing motor 12.
However, if the signal from the frequency signal generation circuit 36 is a voltage signal, it goes without saying that the speed command circuit 26 includes a V/F converter for voltage V/frequency F conversion. First comparator 38
compares the frequency signal from the frequency signal generation circuit 36 and the set frequency signal ₁ from the first frequency setting circuit 40, and operates when both signals match (= ₁ ), and controls the match signal C to the first control. Supplied to circuit 32. The second comparator 42 compares the frequency signal from the frequency signal generation circuit 36 and the set frequency signal ₂ from the second frequency setting circuit 44, and operates when both signals match (= ₂ ) to generate a match signal. D is supplied to the second control circuit 34. Frequency divider/multiplier 4
Reference numeral 6 denotes a frequency divider that lowers the frequency signal from the frequency signal generation circuit 36 by the pole number ratio of the pole change motor 12, and a frequency divider that increases the frequency signal from the frequency signal generation circuit 36 by the pole number ratio of the pole change motor 12. Including peripherals. The first control circuit 32 receives the rise signal A from the rise/fall command circuit 30 and the first comparator 3.
According to the AND logic condition with the match signal C from 8,
The frequency divider/multiplier 46 and the winding switching circuit 1
Operate 4. The second control circuit 34
The frequency divider/multiplier 46 and the winding switching circuit 14 are operated according to the AND logic condition of the falling signal B from the falling command circuit 30 and the coincidence signal D from the second comparator 42.

The embodiment of the present invention has the above configuration, and its operation will be explained next. FIG. 6 shows the output torque when a pole variable motor 12 that can be switched to 2 or 4 poles is used, and the pole variable motor of each number of poles is driven by a variable voltage variable frequency inverter 24. FIG. 6 is a characteristic diagram showing the relationship between speed (rated area), and in FIG. 6, a shows the case of 4 poles, and b shows the case of 2 poles.

Initially, assuming that the load 20 is being driven at low speed, the pole variable motor 12 is set to a motor with a large number of poles (four poles in this case), which is advantageous for low speed rotation. Therefore, in the rated region (allowable load) at this time, the speed between n ₄₁ and n ₄₃ falls within the range shown by characteristic a.

Next, a rise signal A is output from the rise/fall command circuit 30, and this causes the frequency signal generation circuit 36
As the frequency signal from the motor increases, the speed of the pole changing motor 12 also increases. Since the frequency ₁ set by the first frequency setting circuit 40 is associated with the speed of the pole transformer motor 12 _n43 , at this speed the first control circuit 32 outputs the above rising signal A and the first comparator 38.
The frequency divider/multiplier 46 is activated to lower the frequency signal to the speed command circuit 26 to 1/2 of the pole ratio, and the winding switching circuit 14 is activated. The number of poles of the above pole transformer motor 12 is 4.
Convert from polar to bipolar. At this moment, the windings of the pole transformer motor 12 are disconnected from the inverter device 24 and are in a momentary non-excited state, but the operating time of the winding switching circuit 14 is 10 ms when relay contacts are used, and the semiconductor element If you use
ms, which is sufficiently short compared to the mechanical time constant including the pole variable motor 12 and the load 20, and problems such as the pole variable motor 12 stalling during pole number change do not occur.

When changing the number of poles of the above-mentioned pole changing motor 12 (from 4 poles to 2 poles)
If the speed of (conversion to pole) is _n22 , the frequency of the speed command circuit 26 is 1/2 of that before switching the number of poles, so _n22 = _n43 holds, and almost the same speed is maintained. The number of poles of the pole changing motor 12 can be changed by .
Therefore, in a region where the speed is greater than n ₂₂ (n ₄₃ ), the load 20 is extended over a wide range in the constant torque region up to n ₂₃ and in the constant output region up to n ₂₄ along the rated output region of characteristic b in FIG. It can be driven over a period of time.

Next, for the case of deceleration opposite to the above,
The signal from the rise/fall command circuit 30 becomes a fall signal (low) and causes the frequency signal from the frequency signal generation circuit 36 to fall. When the speed reaches _n22 , the frequency signal from the frequency signal generation circuit 36 and the second set frequency ₂ from the second frequency setting circuit 44 match, and the second comparator 42 generates a match signal d. . The second control circuit 34 is activated upon receiving the above-mentioned falling signal (b) and coincidence signal (d), and operates the frequency divider/multiplier 46 to adjust the frequency signal to the speed command circuit 26 to the pole number ratio (double). At the same time, the winding switching circuit 14
to change the number of poles of the pole changing motor 12 from 2 to 4.
Convert to pole. Here, the pole transformer motor 12 changes its speed from n ₂₂ (=n ₄₃ ) to a low region, that is, the sixth
The motor transfers to the characteristic a shown in the figure and is smoothly driven.

In addition, when switching the number of poles above, the pole changing motor 1
Since the winding No. 2 is temporarily disconnected from the inverter device 24 and then reconnected, a large eddy current may flow if the power phase when the power is turned on again does not match the phase of the residual voltage of the pole changing motor 12. but,
The above transient current flow can be prevented by providing a current limiting reactor (not shown) between the polar transformer motor 12 and the winding switching circuit 14 or by adding a phase matching circuit (not shown) in the inverter device 24. can do.

As described above, the speed control device of the present invention synchronizes the variable voltage variable frequency inverter device, the winding switching circuit for changing the number of poles, and the speed command circuit, and adjusts the number of poles of the motor to By determining the second set frequency and dividing and doubling the command frequency according to the pole number ratio, the number of poles of the pole variable motor is increased at low speeds and decreased at high speeds, and this pole number switching is performed. At the time, the structure was designed to ensure smooth switching so that the shock caused by speed fluctuations to the load was small, so when a conventional polar variable motor was driven by commercial power, intermittent shifting caused problems such as shock during switching, and conventional This eliminates the inconvenience of having a narrow rated range (drive range) when a general-purpose electric motor is driven by a variable voltage variable frequency inverter, and allows the speed to be continuously varied over an extremely wide variable speed range (use range). effective.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the speed control system of a conventional pole-change induction motor, Figure 2 is a characteristic diagram showing the relationship between speed and time of the control system, and Figure 3 is a diagram of a conventional general-purpose induction motor using an inverter. A block diagram of a speed control system in the case of variable speed drive, Fig. 4 is a characteristic diagram showing the relationship between torque and speed showing the usable rated range of the control system, and Fig. 5 is a diagram showing the relationship between pole number conversion induction motor of the present invention. A block diagram showing the configuration of one embodiment of the speed control device, and FIG. 6 is an output torque versus speed characteristic diagram showing the rated range of the drive system when the speed control device of FIG. 5 is used. The same parts in each figure are denoted by the same symbols, 10 is a commercial power supply, 12 is a pole conversion induction motor, 14 is a winding switching circuit, 16 is a command circuit, 18 is a power transmission mechanism, 20 is a load, and 22 is a general purpose Induction motor, 24 is an inverter device, 26 is a speed command circuit, 30 is a rise/fall command circuit, 32 is a first control circuit, 34 is a second control circuit, 36 is a frequency signal generation circuit, 38
is a first comparator, 40 is a first frequency setter, 42 is a second comparator, 44 is a second frequency setter, 46 is a frequency divider/multiplier, and 28 is constituted by the members 30 to 46 above. This is a sequence control circuit.

Claims (1)

[Claims] 1. A pole conversion induction motor, an inverter device that varies voltage and frequency, a winding switching circuit of the pole conversion induction motor, a speed command circuit that gives a frequency and/or voltage command to the inverter device, and a a rise/fall command circuit that commands an increase or fall in the speed of the number conversion induction motor; a frequency signal generation circuit that generates a frequency signal based on a signal from the rise/fall command circuit; and a first frequency signal generator that sets a first frequency. a frequency setting circuit, a second frequency setting circuit that sets a second frequency, a first comparator that compares a set frequency signal from the first frequency setting circuit and a frequency signal from the frequency signal generation circuit; a second comparator that compares the frequency signal from the second frequency setting circuit and the frequency signal from the frequency signal generation circuit; and a second comparator that compares the frequency signal from the second frequency setting circuit with the frequency signal from the frequency signal generation circuit; a frequency divider/multiplier that divides or multiplies the frequency according to the frequency and supplies the frequency signal to the speed command circuit; and a rise signal from the rise/fall command circuit and a coincidence signal from the first comparator. It operates in response to the above frequency division and
A first circuit that operates the frequency multiplier and the winding switching circuit.
a control circuit, and a second control circuit that operates upon receiving a falling signal from the rise/fall command circuit and a coincidence signal from the second comparator, and operates the frequency divider/multiplier and the winding switching circuit. A pole number conversion induction motor speed control device comprising: