JPS60141192A - Capacity variable type inverter - Google Patents

Abstract

PURPOSE:To save the energy, to simplify a heat sink unit and to increase the lifetime of a switching element by detecting the current of a motor and controlling the level of power in response to a load. CONSTITUTION:A plurality of types of sinusoidal patterns of different peak values are written in a ROM block 6. A detected current value and a reference current value are compared, and address signals Ax, Ay are applied. A ROM block 6 which receives an address signal selects a sinusoidal pattern having a high peak value if no signal of Ax is presented, a sinusoidal pattern having a low peak value is selected if a signal of Ax is presented but no signal of Ay is presented, and a sinusoidal pattern having a slightly high peak value is selected if a signal of Ay is presented. Thus, when a load varies at a starting time or at a constant speed rotating time, a motor supplying power is controlled in response thereto.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to an impark that controls an AC motor, and more specifically, it has a ROM in which a sine wave is written and controls the power supplied to the AC motor. The present invention relates to a PAM inverter or a PWM inverter.

(b) Conventional technology Originally, AC motors had an energy-saving function that automatically adjusted power consumption according to the load. Once started, the impedance decreases and increases as the load increases and the current also increases and decreases. We are prepared. Therefore, if we only look at this aspect, there is no need for the inverter that supplies power to the motor to have a particular energy-saving function. For example, when a centrifugal separator is driven by a hysteresis motor similar to a simple synchronous motor, after the motor is started, it operates at a constant speed with a light load, almost no load, but from a power source, such as a conventional inverter,
A small amount of power corresponding to this light load is supplied, and energy-saving operation is automatically maintained.

However, when starting the electric motor, a load is applied due to the moment of inertia, so the power supplied to the electric motor temporarily increases. Therefore, in order to speed up the rise of rotation, a mechanism is required to adjust the supplied power at startup. Therefore, conventionally, the power supply was limited by changing the power supply voltage, but using this method, the inverter was complicated and
Moreover, it became expensive.

(c) Purpose of the present invention In view of the problems of the prior art described above, the present invention detects the current of the motor with a simple mechanism without changing the power supply voltage, and utilizes this to detect the current of the motor when starting the motor. , it supplies an appropriately adjusted high level of power, and when it enters constant speed operation after startup, it automatically switches the internal circuit and controls to supply a low level of power commensurate with the operating load, thereby saving energy. energy.

An object of the present invention is to provide a sine wave inverter that can simplify the heat sink and extend the life of switching elements.

(d) Structure of the Invention The variable capacity inverter of the present invention is a pulse height modulation (PAM) inverter having a fixed memory (ROM) in which a sine wave pattern representing power supplied to an AC motor is written, or a pulse width modulation inverter. (PWM) in the inverter, a motor current detection means, a comparison means for comparing the detected current value with a plurality of preset reference current values, a logic processing means for logically processing the comparison result and transmitting a signal;
The ROM is equipped with a ROM in which sine wave patterns representing a plurality of different power values are written so as to receive the above signal and change the power value output from the inverter in accordance with the signal, and the magnitude of the detected motor current value is The present invention is characterized in that the electric power supplied to the electric motor can be controlled in accordance with the above.

(E) Embodiments Examples of the present invention will be described below based on the drawings. The embodiment shows a case in which the present invention is applied to a PWM inverter that controls a hysteresis motor having a two-phase AC stator winding that drives a centrifugal separator.

FIG. 1 is a block diagram showing the electric circuit of the inverter of the above embodiment. First, the configuration of the embodiment will be described based on this diagram.

Ll and L2 are two-phase stator windings of the motor. Transistor Tr1. Tr2. Tra, Tz.

The inverter 12 supplies two-phase AC power of a predetermined frequency and a predetermined voltage to the electric TA winding.

Vl and V2 are DC power supplies for the inverter.

The pulse conversion circuit 11 receives the output of sine wave height data from the ROM block 6, converts it into a pulse width,
A control pulse voltage is output to each transistor of the inverter 12. The ROM block 6 has data of various sine wave heights written in advance, and sequentially reads these data according to the input address signal and outputs them to the pulse conversion circuit 11. The frequency divider 10 determines the timing of conduction of each transistor by distributing the oscillation pulse of the oscillator 9 corresponding to each of the above-mentioned transistors.
An address signal for sequentially reading out the sine wave height data written in the OM block 6 is transmitted to the block 6. Resistor R1 detects the current value of the motor, converts it into a voltage value, and outputs it to each of comparators 1 and 2. Each of comparators 1 and 2 receives the signal of the motor current detection value output from this resistor R1, and transmits the signal to the resistor VR attached to each of the comparators 1 and 2.
It compares the first reference current value and the second reference current value set by I and VH2, and outputs the comparison result to the logic circuit 8. The above logic circuit 8 having the AND circuit 7 receives the outputs of the above comparators 1 and 2, processes them logically, and sends the sine of the peak value of the height corresponding to the motor current value to the ROM block 6. Sends an address signal to select and output wave write data.

Next, the action will be explained.

The transistors Tr1 and Tr2 in the first transistor column shown in FIG. If the current in the transistor row and the current in the second transistor row have a phase difference of 90 degrees, the two-phase stator winding of the motor, L2, has a two-phase alternating current. flows in, a rotating magnetic field is formed in the stator, and at the same time residual magnetic poles are formed in the rotor core due to hysteresis, and the motor starts rotating.

Now, Trl, Tr2. The signal applied to the bases of the transistors Tra and Tra is a pulse train obtained by converting a sine wave into a pulse width.
These were written in the four ROMs in block 6 as peak values of sine waves whose phases were shifted from each other, and these were sequentially read out by the address signal output from the frequency divider.
Further, these are converted into pulse widths by the pulse width conversion circuit 11.

Now, in this ROM block 6, for example, in FIG.
Alternatively, multiple types of sine wave patterns with different peak values as shown in FIG. 3 are written. Also, the motor current is detected by the resistor R1 and converted to a voltage signal Vx, and compared with the voltage set by the resistor VR (set as the first reference current value), it is determined that Vx is higher. Comparator 1 sends a signal when it is smaller, and comparator 2 also sends a signal when VxO is larger than the value set by resistor VR2.
Set it up. The output signals of these comparators 1.2 are processed by a logic circuit 8 and input to a ROM block 6.

That is, the output of the comparator 1 is used as the address signal Ax, and the output of the comparator 1.2 is processed by the AND circuit 7.
Let D be the address signal Ay, and these address signals R
Input to OM block 6. When the ROM block 6 receives these address signals, there is no Ax signal,
Select a sine wave pattern with a high peak value as shown in Figure 2,
If there is an Ax signal but no Ay signal, select a sine wave pattern with a low peak value as shown in Figure 3, and
If there is a y-fold signal, a sine wave pattern with a slightly higher peak value between those in FIGS. 2 and 3 is selected, and these selected patterns are output to the pulse width conversion circuit 11 at the next stage.

When a large load due to the moment of inertia is applied to the motor, such as when starting the motor, the output Ax signal of the comparator 1 disappears, and in this case, the ROM block 6 automatically outputs
Since data of a sine wave with a high peak value as shown in FIG. When the rotation starts, there is an Ax signal, but the Ay signal disappears, and the sine wave data with a low peak value is sent to the pulse conversion circuit 1.
1, the output power and supply to the motor decreases,
Unnecessary electric motor heat generation and power loss are reduced. Furthermore, when accelerating operation is started from constant speed rotation, the load on the electric motor also increases, so that output Ay from AN1 circuit 7 is generated. Therefore, data of a sine wave with a slightly high peak value is stored in the ROM.
The output from block 6 is to the circuit JO, with the result that the power supplied to the motor is increased.

As described above, if the inverter of the present invention is used, power that is appropriately adjusted in response to changes in the motor current value depending on the operating state of the motor is supplied to the motor, resulting in an energy-saving effect in power supply. Effects include a reduction in the load on the impark switching element, a simplification of the radiator due to the reduction in heat generated by the motor, and a favorable effect on centrifugal sedimentation particle size distribution measurement due to the reduction in heat generated on the driven equipment side.

In this embodiment, a comparator is used, and the RO
We have described the case where a sine wave pattern is selected and read from M block 6, but in this case, a comparator is added so that if an overcurrent flows in the motor circuit, a pattern with a peak value of zero is selected. In this way, a motor protection circuit can be formed that turns off the power when an overcurrent occurs. Additionally, by using arithmetic elements such as microcomputers in comparators and logic circuits, it becomes possible to create even more detailed correspondence between the detected motor current value and the selected sine wave pattern, allowing for precise power supply control. It can be performed.

In addition, in the example, the case of PWM was taken up, but PA
It is also possible to use M. Further, although the inverter circuit uses transistors in the above description, it is also possible to use a silicon conductor rectifier (SCR). Furthermore, in the embodiment, the case of a two-phase winding hysteresis motor has been described, but the case of a two-phase winding motor can also be easily accommodated by modifying the inverter circuit using known techniques. can. Furthermore, in the embodiment, a DC battery is used as the pie-break power source, but instead of this, a rectified three-phase AC or single-phase AC can also be used.

(f) Effects of the Invention When an AC motor drives a load, such as a centrifugal separator or a centrifugal sedimentation particle size distribution analyzer, using the inverter of the present invention allows the motor current to change in response to various operating conditions of the motor. Accordingly, the power supplied to the motor can be appropriately adjusted, and as a result, energy saving in power supply and simplification of the motor heat radiator can be achieved. In addition, when a device driven by an electric motor is sensitive to temperature changes, such as an electrically driven centrifugal sedimentation particle size distribution analyzer, the present inverter is very effective in reducing the heat generated by the electric motor. moreover,
According to the present invention, effects such as extending the life of switching elements of an inverter and utilizing the switching elements for overcurrent protection can be obtained.

Note that the inverter of the present invention can be constructed by adding a few simple devices to the inverter of the through hole, and produces the above-mentioned effects, so it is an extremely economical device.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings show an embodiment of the present invention, FIG. 1 is a block diagram showing its electric circuit, and FIG. 2 shows a high peak value output from the ROM block 6 to the pulse conversion circuit 11. FIG. 3 is a waveform diagram showing a sine wave pattern with a similarly low peak value. 1--Comparator 1 2--Comparator 2 6--ROM block 8-Logic circuit 9--Oscillator 10-Frequency divider 11--Pulse width conversion circuit 12--Inverter LI+L2'-- - Motor stator winding R1 - motor current detection resistors Trl, Tr2. Tr3. Tr4 ~ Inverter transistor Vl, V2 - Inverter DC power supply

Claims (1)

[Claims] Pulse altitude a having a fixed memory (ROM) in which a sine wave pattern representing the power supplied to the AC motor is written.
ll (PAM) inverter or pulse width change @
(PWM) in the inverter, a motor current detection means, a comparison means for comparing the detected current value with a plurality of preset reference current values, a logic processing means for logically processing the comparison result and receiving a signal; The ROM is equipped with a ROM in which a sine wave waveform expressing a plurality of different power values is written so as to receive the above signal and change the power value output from the inverter in response to the above signal, and to adjust the magnitude of the detected motor current value. A variable capacity inverter configured to control the power supplied to the motor accordingly.