JPH1045341A - Speed control device for elevator inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To absorb torque in a descending direction applied to an elevator cage, without increasing a torque boost voltage level. SOLUTION: In an open-loop control, wherein a slip frequency is determined by an operation part 9 from the D.C. current of an inverter 4 for driving an induction motor 5 adopted as the prime mover for a hoisting drum type elevator, this slip frequency is added or subtracted to/from a speed directive to operate the voltage and frequency of the inverter by an operation part 10 with the slip frequency as a speed directive; the induction motor can obtain a torque boost by a frequency, by absorbing a torque part constantly applied in the descending direction of an elevator cage, and adding or subtracting a frequency in accordance with the torque part to/from the output frequency of the inverter, in the operation part 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an open-loop speed control device for an induction motor using an inverter for an elevator, and more particularly to a speed control device for compensating for a downward torque constantly applied to a winding type elevator car.

[0002]

2. Description of the Related Art An elevator motor is an induction motor,
When this induction motor is driven by an inverter having a variable voltage / variable frequency (VVVF), the speed control of the induction motor generally employs open loop control using a voltage type inverter for a low-speed elevator.

The open-loop speed control system seeks to obtain acceleration, constant speed, and deceleration that match the speed pattern by controlling the output frequency and output voltage of the inverter according to the speed pattern.

This control method eliminates the need for a speed detector and reduces the cost, and eliminates the need for backup means for failure of the speed detection system. Since there is no system, the landing accuracy deteriorates due to load fluctuations (such as the number of occupants).

[0005] As a speed control method for solving this problem,
There is a method in which a slip frequency is obtained by detecting a direct current in a constant high-speed region of an elevator, and a motor speed correction and a torque correction are performed from the slip frequency to improve the accuracy of the landing position of the elevator car (for example, Japanese Patent Laid-Open No. -25
No. 2193).

Further, in order to determine a slip frequency which eliminates the influence of static friction torque in a mechanical system from an induction motor to an elevator car operation, for example, Japanese Patent Application Laid-Open No. Hei 4-3041
No. 96 discloses a method of obtaining a value proportional to a slip frequency from a difference between a DC current detection value during no-load excitation of an induction motor and a DC current detection value during constant speed operation.

On the other hand, in the acceleration operation of the elevator, the generated torque is insufficient due to the primary resistance of the induction motor.
To compensate for this torque, a so-called torque boost is often performed in which the ratio of the output voltage to the output frequency of the inverter is increased.

[0008] In the elevator to which the torque boost function is added, the followability to the speed command is improved during acceleration to improve the ride comfort. This mode is as shown in FIG. 5 (a) or (b). And a characteristic fV ₂ obtained by adding a torque boost amount indicated by oblique lines to a characteristic fV _{1 in} which the output voltage ratio to the output frequency of the inverter is constant.
To drive the motor.

[0009]

FIG. 6 shows a schematic configuration of a winding drum type elevator having no counterweight. A drum (winding drum) B is driven from an electric motor A via a gear, and is wound around the drum B. The elevator car D is directly raised / lowered by the rotating wire C. E is a sheave.

[0010] The open loop speed control in which the torque boost is applied to the winding drum type elevator has the following problems.

In the case of a roll-type elevator, an elevator car D
Always generates a load in a direction of decreasing, and when the brake is opened, a descending force acts on the elevator car D. For this reason, the elevator control circuit applies a current to the electric motor to generate a balancing torque by supplying a current to the electric motor before the brake opening command at the start of the lifting / lowering control, and the torque boost prevents the elevator car from lowering.

To adjust the balance, a DC current is supplied to the electric motor, and the voltage level of the torque boost is increased until the elevator car does not descend at the timing when the brake is opened.

However, in this case, the voltage and current of the motor increase due to the generation of the balancing torque, which causes overheating of the motor and overheating and breakage of the inverter main circuit element.

It is an object of the present invention to provide a speed control device that absorbs a downward torque applied to an elevator car without increasing a torque boost voltage level.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention obtains a slip frequency from a DC current of an inverter that drives an induction motor serving as a prime mover of a winding drum type elevator, and determines the slip frequency by a speed command. An open-loop control system that performs speed control by correcting the load change by adding and subtracting the load change, and an inverter for an elevator that performs a torque boost control at the time of acceleration. A frequency bias means for absorbing by control is provided.

The bias means adds an output frequency component proportional to the speed command in the direction of raising the elevator car to a frequency boost at which the speed command has a maximum value at zero, and a speed command in the direction of lowering the elevator car. The output frequency is obtained by subtracting the frequency boost that is the maximum value when the speed command is zero from the output frequency component proportional to the output frequency component.

Further, the bias means adds a constant frequency boost to an output frequency component proportional to the speed command in the direction of raising the elevator car, and adds an output frequency component proportional to the speed command in the direction of lowering the elevator car. The output frequency is obtained by subtracting a fixed frequency boost.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a configuration diagram of a speed control device of an induction motor for a winding drum type elevator according to an embodiment of the present invention.

The AC power of the AC power supply 1 is converted into DC power by the rectifier 2 and smoothed by the capacitor 3. The DC power is converted into AC power whose output frequency and voltage are controlled by the voltage-source inverter main circuit 4 and supplied to the induction motor 5 which becomes the prime mover of the winding type elevator.

The operation frequency and voltage of the inverter main circuit 4 are controlled by obtaining a gate pulse whose frequency and pulse width are controlled by the base drive circuit 7 in accordance with a voltage / frequency control signal from the control device 6. On / off control of the switch is performed.

The control device 6 has a microcomputer construction and includes a speed command calculating section 8, a current / slip conversion calculating section 9, and a voltage / frequency command calculating section 10, and corrects the speed command with the slip frequency f (s). This causes the motor speed to match the speed command.

The speed command calculation section 8 calculates and generates a speed pattern having an acceleration / deceleration determined for the elevator and having a constant speed time corresponding to the elevating distance (floor moving distance). The voltage / frequency command calculation unit 10 obtains an inverter operating frequency and a voltage from a value obtained by adding and subtracting a slip frequency f (s) to a speed command according to a speed pattern. In calculating the voltage for this frequency, a torque boost adjustment as shown in FIG. 5A or 5B is performed.

The current / slip conversion operation unit 9 directly obtains the slip frequency f (s) from the inverter DC current detection signal by the current detector 11 and the current detection circuit 12 without detecting the load torque. This operation is basically the following equation

[0024]

## EQU1 ## The slip frequency f (s) is obtained by calculating f (s) = (excitation current)-(current at constant speed operation) .times.slip correction coefficient k.

This calculation utilizes the characteristic that the inverter DC current is proportional to the generated torque of the motor when the motor operating speed is constant (constant speed). The DC current during no-load operation of the motor is obtained in advance. , Slip correction coefficient k
The slip frequency f (s) is obtained by taking in the current detection value at a constant speed by setting.

This calculation is performed a plurality of times in order to eliminate noise and variations in detection, and a more accurate slip frequency f (s) is obtained by providing a first-order lag with a filter in order to reduce the influence of noise. Can be.

In the configuration described above, in the present embodiment, the frequency control of the electric motor 5 is performed in order to absorb, as the generated torque of the electric motor, the downward load which is always generated in the winding-type elevator car.

As means for generating torque in the electric motor,
There is a way to control the frequency. Utilizing this method, a frequency corresponding to the balance torque is added to the frequency of the inverter applied to the motor for the winding drum type elevator, and the bias is added.

This bias addition is set by the voltage / frequency command calculator 10. The voltage / frequency command calculation unit 10 converts the slip frequency f into a speed command according to the speed pattern.
The inverter operating frequency and voltage are obtained from the value obtained by adding and subtracting (s), and the torque boost adjustment is performed to calculate the voltage with respect to the frequency.

Here, the voltage / frequency command calculation unit 10
After the operating frequency of the inverter is obtained, a frequency corresponding to the balanced torque is added to the frequency to obtain the operating frequency of the inverter.

FIG. 2 shows the output frequency characteristics of the bias addition to the speed command given to the voltage / frequency command calculation unit 10. FIG. 2 (a) shows a case where the elevator car is raised (UP) by rotating the motor forward. (B) shows a case where the elevator car is lowered (DOWN) by reversing the electric motor.

In the figure, a broken line ff ₁ indicates a speed command (calculation unit 8
An original output frequency characteristic which is proportional to) obtained by adding the slip amount of the computation unit 9 of a command, a solid line ff ₂ is the output frequency characteristic obtained by adding or subtracting to generate the balance torque to the speed command, The hatched portion corresponds to the torque boost amount depending on the frequency.

In the UP direction, an output frequency is obtained by adding a frequency component proportional to the speed command to a frequency boost amount which becomes a maximum value when the speed command is zero and becomes zero at the highest frequency.

In the DOWN direction, an output frequency is obtained by subtracting a frequency boost amount which becomes a maximum value when the speed command is zero and becomes zero at the highest frequency, to a frequency component proportional to the speed command.

By the torque boost by this frequency,
On the UP side, it is possible to effectively generate torque in a direction in which the elevator car does not descend, and on the DOWN side, it is possible to effectively generate torque in a direction in which the elevator car does not increase the descending speed.

FIG. 3 shows another embodiment of the present invention, and shows an output frequency characteristic of bias addition with respect to a speed command given to the voltage / frequency command calculation unit 10. Portions figure differs from FIG. 2 is that the output frequency ff ₂ plus or minus the torque boost frequency of constant value for the output frequency ff _1.

In the present embodiment, only the operation of adding or subtracting a constant value to or from the output frequency proportional to the speed command is required for the torque boost by frequency, and the operation is simplified.

FIG. 4 shows another embodiment of the present invention. The difference from FIG. 2 is that the amount of torque boost by frequency is added or subtracted below an arbitrary frequency in a region up to the highest frequency.

[0039]

As described above, according to the present invention, in a winding drum type elevator inverter, the amount of torque constantly applied in the descending direction of the elevator car is absorbed by the output frequency control of the inverter. Is increased only by the torque boost control at the time of acceleration, and the voltage and current of the electric motor are suppressed to generate the balancing torque in the winding drum type elevator, so that overheating and overheating and breakage of the inverter main circuit element can be prevented.

Further, since a boost component is added in a direction to stabilize the elevating operation of the elevator car, riding comfort can be improved.

[Brief description of the drawings]

FIG. 1 is an apparatus configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram (part 1) of a frequency control characteristic in the embodiment.

FIG. 3 is a frequency control characteristic diagram (part 2) according to the embodiment;

FIG. 4 is a frequency control characteristic diagram (part 3) according to the embodiment;

FIG. 5 is an explanatory diagram of torque boost adjustment by an output voltage.

FIG. 6 is a schematic configuration diagram of a winding drum type elevator.

[Explanation of symbols]

 4 inverter main circuit, 5 induction motor, 6 control device, 7 base drive circuit, 8 speed command calculation unit, 9 current / slip conversion calculation unit, 10 voltage / frequency command calculation unit, 11 current Detector, 12 ... Current detection circuit.

Claims (3)

[Claims] A slip frequency is obtained from a DC current of an inverter that drives an induction motor serving as a prime mover of a winding drum type elevator, and the slip frequency is added to or subtracted from a speed command to perform speed control in which a load change is corrected. An elevator inverter using a loop control method and performing torque boost control during acceleration, comprising: frequency bias means for absorbing a torque always applied in a descending direction of an elevator car by output frequency control of the inverter. Speed control device for inverter. 2. The method according to claim 1, wherein the bias means adds a frequency boost component at which the speed command becomes zero to a maximum value to an output frequency component proportional to the speed command in a direction in which the elevator car is raised. 2. The speed control device for an elevator inverter according to claim 1, wherein an output frequency is obtained by subtracting an output frequency component proportional to the speed command from a frequency boost at which the speed command has a maximum value at zero. 3. The bias means adds a constant frequency boost to an output frequency component proportional to the speed command in the direction of raising the elevator car, and adds an output frequency component proportional to the speed command in the direction of lowering the elevator car. The speed control device for an elevator inverter according to claim 1, wherein the output frequency is obtained by subtracting a fixed frequency boost.