JPH10291783A - Induction motor or inverter hoist - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the capacity of a resistor for discharging regenerative power and a V/F inverter by lowering output voltage by a previously prescribed slip quantity when a motor reaches a target speed command value as the highest speed, and maintaining the voltage fixed. SOLUTION: A cotating speed detector 8 detects rotating speed of an induction motor 4, a slip computing part 13 inputs it, the slip computing part 13 inputs simultaneously a frequency control signal 10a from a frequency signal control part 10, and the slip computing part 13 computes the slip of the induction motor 4. An output voltage reducing signal 13a is input to an output voltage control part 11 in the range of settling the slip in a prescribed value, and voltage impressed on the induction motor 4 is reduced. Hereat, in a state of acceleration, in addition to increase output voltage toward a target speed, output frequency is increased. In a fixed speed operation state, the output frequency is kept fixed, and the output voltage is reduced so as to continue the state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor with a rotation speed detector driven by a V / F control inverter, and more particularly to an induction motor suitable for driving an electric hoist or an inverter hoist using the induction motor. About.

[0002]

2. Description of the Related Art V / Fs conventionally used for hoist driving
As shown in FIG. 6, the output voltage of the control inverter is different from that of the inverter using the same V / F pattern in the hoisting operation and the hoisting operation as shown in FIG. In some cases, the / F pattern is selected and applied to an induction motor. In FIG. 7, the upper V / F pattern is used for winding, and the lower V / F pattern is used for winding. And
In any case, the output voltage uses a predetermined constant value.

[0003]

According to the above-mentioned prior art, the voltage applied to the induction motor is mainly focused on securing the torque during winding, and is assumed to have a value at which the rated torque can be secured at least. In the case of the lowering operation, even if the load is the same, the torque required for the hoisting operation is not necessary. or,
The excess positive power is discharged by a positive power discharge resistor to suppress heat generation due to a large current.However, it is necessary to use a large capacity positive power discharge resistor that can withstand high power. Have been forced. The higher the initial voltage at which the regenerative action starts, the higher the regenerative power is, so it is desirable that the initial voltage be low.

[0004] Further, since a high voltage must be constantly applied to the motor, a large-capacity inverter device is required, and the inverter device is large and heavy.

On the other hand, when driving a hoist or a similar load, it is possible to drive the load sufficiently at a constant speed after reaching the maximum speed even if the maximum speed is not reached.

Focusing on the above, the present invention provides a method of driving a load at a constant speed lower than the maximum speed during constant speed operation after reaching the maximum speed, suppressing generation of regenerative power, and regenerating regenerative power. And the size of the resistor for
An object of the present invention is to provide an induction motor or an inverter hoist in which the capacity of an F control inverter is reduced.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an AC power supply, a circuit for rectifying the power supply to DC, a power module connected to the circuit to apply a voltage to the motor, and a target speed which is the highest speed for the motor. An induction motor comprising: means for giving a command value; means for applying an output voltage to the motor along a V / F pattern to accelerate the motor so as to reach the target speed command value; and means for detecting the speed of the motor. Alternatively, in the inverter hoist, means for detecting whether the motor has reached a target speed command value that is the highest speed,
This is achieved by providing means for reducing the output voltage by a predetermined slip amount when the target speed command value is reached, and means for maintaining the output voltage constant after the output voltage drops.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an inverter-driven hoist.

In the figure, 1 is a diode module for rectifying a commercial 220 V three-phase AC, 2 is a DC unit, 2a is a smoothing capacitor, 3 is a power module for reconstructing a three-phase AC frequency-converted from DC by switching operation. Reference numeral 4 denotes an induction motor, reference numeral 5 denotes a resistor for positive power discharge, and reference numeral 6 denotes a resistor for positive power discharge when the voltage of the DC unit 2 is increased mainly by the positive power generated from the induction motor during the lowering operation. A regenerative controller for discharging power to the heater 5, a brake 7 for holding a load by frictional force when the induction motor is in a non-energized state, a rotation speed detector 8 for detecting a rotation speed of the induction motor, and a rotation speed 8a. A speed signal, 9 is an operation input detection unit for detecting the input of an operation command and a speed command, 10 is a frequency signal control unit, 10a is a frequency control signal, 11 is an output voltage control unit, and 11a is an output power control unit. Signal, 12 a frequency control signal 10
a and the output voltage signal 11a
, A slip calculation unit for calculating the slip of the induction motor 4 from the frequency control signal 10a from the frequency signal control unit 10 and the rotation speed signal 8a from the rotation speed detector 8, and 13a an output. A voltage reduction signal, 14 is a brake control unit that releases a brake according to an operation command, 15 is an operation switch that inputs an operation command to the operation input detection unit 9, 15a is a hoisting operation command button,
15b is a lowering operation command button, 16 is an operation input detector 9
This is a speed indicator for inputting a speed command to the speed indicator.

The inverter hoist to which the present invention is applied is constituted by the above components and circuits.

Next, the operation of the inverter hoist will be described with reference to FIG.

First, an arbitrary speed is set by the speed indicator 16. Next, the hoisting operation command button 15a or the hoisting operation command button 15b of the operation switch 15 is turned ON.

The operation input detector 9 detects a command from the speed indicator 16 and the operation switch 15 and sends the command signal to the frequency signal controller 10 and the output voltage controller 11.

Frequency signal controller 10 and output voltage controller 1
1 generates a frequency control signal 10a and an output voltage signal 11a in accordance with a preset V / F pattern, and provides them to a power module driver 12.

The power module driver 12 performs switching driving of the power module 3 according to a given signal.

The diode module 1 is connected to a three-phase AC power supply. The output of the diode module 1 is rectified by the DC section 2 and smoothed by the smoothing capacitor 2a before being applied to the power module 3.

The power module 3 is switching-controlled by the power module driver 12 described above, generates a three-phase alternating current again from the DC voltage, and drives the induction motor 4.

At the same time, the brake control unit 14 receiving the command from the operation input detection unit 9 releases the brake 7, and the induction motor 14 starts rotating. Thereafter, acceleration is started toward the set speed, and finally a constant speed operation is performed at the speed set by the speed indicator 16.

In a hoisting operation with a load suspended, a positive electric power is generated from the induction motor 4 and the voltage of the DC section 2 rises.

At this time, the regenerative controller 6 monitors the voltage value, and when the voltage value exceeds a specified value, the regenerative controller 6 discharges the voltage to the positive power discharging resistor 5 to suppress an increase in voltage.

The rotation speed detector 8 detects the rotation speed of the induction motor 4 and inputs the detected rotation speed to the slip calculator 13. The frequency control signal 10a from the frequency signal control unit 10 is input to the slip calculation unit 13 at the same time, whereby the slip of the induction motor 4 is calculated. The output voltage reduction signal 13a is input to the output voltage control unit 11 within a range where the slip falls within a specified value, and reduces the voltage applied to the induction motor 4.

The specified value of the slip is determined so that the moving speed of the load falls within about ± 20% of the set speed.

FIGS. 2 and 3 are time charts showing states of the output voltage and the output frequency from the operation input ON to OFF.

In the period from t1 to t2, the output voltage is increased from V0 to V1 and the output frequency is increased from f0 to f1 in accordance with the basic V / F pattern shown in FIG.

The section from t2 to t3 is a constant speed operation state.
The output voltage here is the basic V / V as shown by the dotted line.
Although fixed to V1 determined by the F pattern, the present invention keeps the output frequency constant at f1, reduces the output voltage to V2 according to the flowchart shown in FIG. 5, and continues that state.

Next, the flowchart of FIG. 5 will be described.

Step S1 is a step of accelerating to a preset target speed. Step S2 is shown in FIG.
This is a step of accelerating the motor by outputting in accordance with the basic acceleration pattern. Next, it is checked in step 3 whether the motor has reached the target speed.

If the target value has not been reached, step S2
Then, the acceleration operation is continued. When the rotation speed reaches the target value (the output voltage V1 in FIG. 2), the rotation speed is detected (Step S).
4) Slip from the target value is calculated (step S)
5).

In step S6, it is checked whether the slip (difference speed) from the target value is within a predetermined slip value, for example, 20% as described above. The process proceeds to control to reduce the output voltage, and returns to step 4. This operation is continued until the slip reaches a predetermined specified value, for example, 20%. When the slip reaches 20%, the voltage of 80% of the target value (FIG. 2)
The output voltage V2) is fixed and the low-speed operation is continued, and the winding is lowered (step S8). The slip amount can be increased as the load is smaller.
It can be set to 0%.

As described above, when the output speed is reduced to about 70 to 80% when the maximum speed is reached, the positive power (current) is greatly reduced as described above, and the inverter power is accordingly reduced. The load is reduced, and the capacity of the inverter can be reduced.

Further, since the regenerative power (current) is greatly reduced, the size and weight of the regenerative power discharge resistor can be reduced and the size and weight can be reduced. An electric motor and a hoist can be obtained.

During the period from t3 to t4, the output voltage is decreased from V2 to V0, and the output frequency is decreased from f1 to f0 in accordance with the decrease of the output voltage, contrary to the acceleration. I do.

FIG. 2 shows the case of high-speed operation, and FIG. 3 shows the case of low-speed operation.

In this embodiment, the slip of the induction motor is used as a determination value for fixing the output voltage. However, as another means, a value obtained by comparing a speed signal given from a speed indicator with a rotation speed is used as a determination value. It is the same as

As a configuration for realizing the function, there are a case where the function is realized by hardware using a semiconductor element and a case where the function is realized by software using a microcomputer.

[0037]

As described above, according to the present invention, during constant speed operation after reaching the maximum speed, the load is driven at a constant speed lower than the maximum speed. In addition, it is possible to provide an induction motor or an inverter hoist in which the capacity of the regenerative power discharge resistor is reduced and downsized, and the capacity of the V / F control inverter is reduced.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of an inverter drive hoist to which the present invention is applied.

FIG. 2 is a time chart at the time of high-speed operation of output voltage and output frequency.

FIG. 3 is a time chart at the time of low-speed operation of an output voltage and an output frequency.

FIG. 4 is a diagram showing a basic V / F pattern.

FIG. 5 is a flowchart of an output voltage reduction process.

FIG. 6 shows V / V when the conventional hoisting operation and the hoisting operation are the same.
The figure which shows F pattern.

FIG. 7 is a diagram showing a V / F pattern when a pattern is selected in a conventional hoisting operation and a hoisting operation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diode module, 2 ... DC part, 2a ... Smoothing capacitor, 3 ... Power module, 4 ... Induction motor, 5
... Resistor for positive power discharge, 6 ... Rotary controller, 7 ... Brake, 8 ... Rotation speed detector, 8a ... Rotation speed signal, 9 ... Operation input detector, 10 ... Frequency signal controller, 10a ... Frequency Control signal, 11: output voltage control unit, 11a: output voltage signal, 12: power module driver, 13: slip calculation unit, 13a: output voltage reduction signal, 14: brake control unit, 15: operation switch, 15a: winding Operation command button, 15b ... Unwind operation command button, 16 ... Speed indicator.

Claims (2)

[Claims] 1. An AC power supply, a circuit for rectifying the power supply to DC, a power module connected to the circuit for applying a voltage to a motor, a means for providing a target speed command value which is the highest speed to the motor, V to reach the target speed command value
In an induction motor including means for applying an output voltage to the motor according to the / F pattern to accelerate the motor and means for detecting the speed of the motor, whether the motor has reached the target speed command value that is the highest speed An induction motor comprising: means for detecting an output voltage; means for reducing the output voltage by a predetermined slip amount when a target speed command value is reached; and means for maintaining the output voltage constant after the output voltage drops. 2. An AC power supply, a circuit for converting the power supply into a rectified DC, a power module connected to the circuit for applying a voltage to an inverter motor for driving a hoist, and a power supply for positive power discharge also connected to the circuit. A resistor, a brake device that performs a braking operation when the hoist is OFF, a means for giving a target speed command value that is the highest speed to the motor, and output to the motor along the V / F pattern so as to reach the target speed command value. An inverter hoist comprising: means for applying a voltage to accelerate the motor; and means for detecting the speed of the motor. A means for detecting whether the motor has reached a target speed command value that is the highest speed, and a target speed command. Means for lowering the output voltage by a predetermined slip amount when the output voltage has reached a value, and means for maintaining the voltage constant after the output voltage drops. Inverter hoist.