JPS58159695A - Controller for motor - Google Patents

Abstract

PURPOSE:To automatically correct the torque of an induction motor when started with reverse rotation by altering the target value of a constant current control system when the motor is reversely rotated. CONSTITUTION:Voltage detectors 12A-12C and a current detector 13 respectively detect the voltage and current of the phases of an induction motor 9. A limiter 14 stores the pattern of determining the characteristic relatioship between the output fM of a tachometer generator 10 in normally rotating direction and the output voltage of an inverter, compares the output voltage of the inverter to the output fM of the actually measured tachometer generator 10 with the output voltage of the inverter in the pattern and produces an output when both output voltages do not coincide. An arithmetic circuit 15 decides the output current value of the inverter in response to the output of the limiter 14. When the motor 9 is reversely rotated, the constant current value supplied from the inverter 8 to the motor 9 is increased in response to the signal from the limiter 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor control device that automatically corrects the torque of an induction motor when the induction motor is started with rotation in the opposite direction.

Conventionally, there has been a device of this type as shown in FIG.

FIG. 1 shows a system in which an induction motor (hereinafter referred to as IM) is driven by a variable voltage/variable frequency (hereinafter referred to as VVVF) inverter.

In Figure 1, there is a cage, t is an overhead wire, and ko is a pantograph.

3 is a current interrupter, S is a high-speed flow reducer, and S is a flow reduction resistor.

6 is a thyristor (OVTH) that fires to protect the inverter when the inverter input becomes excessive; 7 is a filter that blocks surges and harmonics from the outside to the inverter or from inside to outside; g is a VVVF inverter; De is I
M, 10 is IM? The tacho generator that detects the IM speed change (rotation speed) // has a slip frequency pattern fs,
This is an adder that adds the output fm of the tacho generator 10.

In this configuration, the IM speed of the IM device is controlled by the VVVF inverter g, but since the operation of the inverter is not the purpose of this paper, a detailed explanation will be omitted.
The calculation method for speed control is to add the output fM of the tacho generator/θ and the slip frequency pattern fs, and calculate fIN
As V, determine the inverter frequency. That is, control is performed so that the linear equation becomes the basis of control.

fM+f3=rINv, , , (1) If this is shown in a diagram, it will be as shown in Figure 2.

The first figure shows the inverter frequency fIN shown by 5 curves no.
It shows the relationship between V and the motor speed (here as motor frequency) fM shown by a one-curve saw, with the horizontal axis representing the speed V and the vertical axis representing the frequency f. That is, (7)
2, the −C deviation frequency fs is added to fINv&ifM. Therefore, if the inverter is completely lost at the slip frequency fs when the speed is O, the motor will produce torque and gradually accelerate. , continuous acceleration is performed, and constant current control is also performed to keep the IM constant current constant.

If we consider the case of starting after calculating the speed like this, 1. Starting acceleration from a normal flat road is not a problem, but when starting on an uphill slope, it is preferable as described below. This will be explained based on FIG. 3. When starting a vehicle, there is a slight delay between when a start command is issued, a current interrupter, etc. is turned on, and normal torque is generated. As a result, the vehicle begins to move backward to some extent instead of moving forward. Since the tachogenerator that detects the IM speed detects only the absolute speed (frequency) of the IM and cannot clarify the direction in which the vehicle is traveling, it causes calculation difficulties as shown in FIG.

In FIG. 3, the actual fM is as shown by curve i,
As the speed increases in the opposite direction, fM decreases, but since the inverter operation only adds fs to the absolute value f'MK of fM shown in curve 1'3, the following (λ) Perform the operation shown in the formula.

f'M + fs - fINV ・ ・ ・ (J) In this calculation, the actual slip frequency f s (reaf) is expressed by fINV, which is expressed by 1 curve 1/, and 1 curve 1 relative to the actual speed.
Since there is a difference from fM shown by 3, the slip frequency fs
(reaffi) as the speed increases.

It will increase.

In this way, when starting on a slope, the slip frequency of the inverter may increase.

IM speed calculator: If the slip exceeds a predetermined value, the following problems will occur. FIG. 9 is a diagram showing torque characteristics due to slippage, and the horizontal axis shows the slippage S, and the vertical axis shows the torques T and [il]. In the figure, curve i,
is the slip-commercial characteristic curve Ls' of IM's slip-torque characteristic. now.

Suppose that the slip S/, the Sanisse flow, and the torque are I/ and T/, respectively. Next, if the slip increases to SJ -, the current and torque increase to Ia and Tr, respectively, but since constant current control is performed as mentioned earlier, only the slip S- increases and the @ current changes. Don't pay.

In the case of TM, the torque can be expressed by the following equation.

T=R (completed) J@fs However, 7, R is a number, and ■ is the inverter output voltage f!・Nol Frequency fs is the slip frequency.If slip is assumed here, then the composite-order resistance R of IM is.

rl Secondary resistance rko: The secondary resistance f3 becomes the slip frequency, and the secondary resistance becomes small. Therefore, if the inverter voltage is the same, the IM constant current will increase, but since the constant current control of the inverter is effective, the current will be suppressed and the torque will decrease. Therefore, as shown in Figure 3 above, when the vehicle moves backwards, the slip increases and the torque becomes
This causes the axle to recover by 2 and become unable to proceed in the normal direction.

This invention was made in order to solve this problem of the present invention, and the relationship between the frequency of the motor in the forward rotation direction and the inverter output voltage is stored in advance, and the actual measured value of the inverter output voltage is compared to the stored value. By comparison, an electric motor control device is provided which changes the target value of the constant current control system when the electric motor rotates in reverse.

Before explaining one embodiment of the present invention, the general operation of the present invention is schematically shown in FIG.

Figure 5 shows the current controlled to a constant value. This is a phenomenon when the slip is increased to a large value from the viewpoint of the inverter output voltage (INV) with respect to the speed V[.

Curve 1) 6 in the figure is the current 9 curve 1g of constant current control is the inverter output voltage when the current is running normally.

The song @Lj is the inverter output voltage when moving backwards. When running normally, the inverter output increases in response to the speed (frequency) trap, tends to overcome the back emf of the IM, and tries to keep the 1M current constant. However, in parallel mode, the IM impedance becomes small, so the voltage must be reduced so that the current does not increase. Therefore, as shown by the curve 1tVC, the inverter output voltage will decrease with speed.

FIG. 6 shows an embodiment of the present invention that utilizes the characteristics shown in FIG. Components indicated by the symbols l to // in the figure are the same as those shown in FIG. 1, and therefore their explanations will be omitted.

/2A~isc is voltage detection a, (ACPTU, V, W), /Jha IM'ft which detects the voltage between each phase of IM
tlf, detector (ACCT), /da is square: I, 1
The characteristic F ratio between fM and inverter output voltage during rotation is memorized, and the inverter output voltage corresponding to the actually measured fM is compared with the inverter output voltage in the button to determine the value of both inverter output voltages. A limiter circuit that outputs an output if they do not match, /3 is the output v of limiter circuit /4 (
This is an operational circuit (OPC) that is compatible with LMT K and determines the inverter output current value. 16 is a comparator that compares the target value IP of the constant current control system and the signal Im from the IM current detection 5/j during forward rotation.

In the above configuration, the basic calculation operation is the same as that observed in FIG. 18, that is, as slip frequency control.

fM+fs = flNV is calculated, and the 1M current is controlled as constant current control so as to reach the control target value IP. At this time, if the electric car goes backwards, the slip will be large, but the current is controlled at a constant current, so the IM voltage is the inverter voltage ■INv
is reduced. The LMT circuit/da compares the inverter voltage vrNVv which is set at the IMm wave number in the visual field with the standard bump, and deviates from the bump, so to speak, outputs the output V to the comparator/AK output PC and outputs it to the target value IP. As a result, busy schedule ii
Increase the target value of the flow control system. As a result, the inverter current IM increases, and the torque shortage can be solved for a long time.

[Brief explanation of the drawing]

The first layer is a block circuit diagram showing a conventional motor control device,
Figure 1 is a diagram for explaining the normal operation of Figure 1, and Figures 3 and 9 show the operating characteristics of Figure 1 when the vehicle is running backwards.
Figures 5 and 6 are diagrams for explaining the principle of operation of the present invention. FIG. 1 is a block circuit diagram showing a motor control device according to an embodiment of the present invention. In the figure, t is a variable voltage/variable frequency inverter, ?
is a conductive motor, lda is a limiter circuit, is is an arithmetic circuit,
fM is the frequency of the inductive t#Ih machine, vINV is the inverter output voltage, and IP is the constant current value. Figure -2 Figure 3 Giant Horse (Figure -6 Figure

Claims (1)

[Scope of Claims] A motor control device for driving and controlling an induction motor with a constant current using a variable voltage/variable frequency inverter, the frequency of the induction motor and the output of the inverter when the induction motor is rotating in the forward direction. Memorize patterns that represent relationships between voltages. and an IJ mitter circuit that compares an actual value of the inverter output voltage corresponding to the frequency of the induction motor with a value stored in the pattern, and when the induction motor rotates in reverse;
5. A motor control device comprising: an arithmetic circuit that operates to increase the constant current value in response to a signal from the limiter circuit.