JPH11240693A - V/f-control-inverter-driven hoist - Google Patents

Abstract

PROBLEM TO BE SOLVED: To move cargo at the same speed in hoisting it up and lowering it down and even upon a change in load. SOLUTION: The V/F-control-inverter-driven hoist comprises a fundamental frequency output part 13 for outputting a fundamental frequency 33 set in advance corresponding to a working speed the operator desires as a command value for the output frequency of power supplied to an induction motor 4 from an inverter circuit 7, an encoder 8 for detecting the actual rotational frequency of the induction motor 4, and a corrected frequency output part 14 for obtaining the deviation between the synchronous rotational frequency of the induction motor 4 that corresponds to the fundamental frequency and the actual rotational frequency the encoder 8 detects and outputting a corrected frequency that eliminates the deviation as an output frequency command 34 into the inverter circuit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a V / F control inverter drive including an induction motor for performing a hoisting and lowering operation, and an inverter circuit for supplying power of various output frequencies to the induction motor. It relates to a hoist.

[0002]

2. Description of the Related Art Conventionally, a V / F control inverter-driven hoist conventionally performs a slip operation of an induction motor when a heavy load is applied when the same frequency instruction is given for hoisting and lowering in a low-speed region where torque is hardly generated. In order to correct the difference in speed, separate speed parameters are provided for hoisting and lowering, and by specifying different frequencies for hoisting and lowering, the apparent operating speed is adjusted. ing.

[0003] Here, referring to FIG.
The F control inverter driven hoist will be described.

The hoist includes a load block 1 for hanging a load or the like, a wire 2 for suspending the load block 1, a drum 3 around which the wire 2 is wound, and an induction motor 4 for rotating the drum 3. A speed reducer 5 for reducing the rotation speed of the induction motor 4, a brake 6 for stopping the rotation of the induction motor 4, an inverter circuit 7 for driving the induction motor 4 at an arbitrary rotation speed, and a control circuit for controlling the inverter circuit 7 And an operation panel 20 operated by an operator. The operation panel 20 includes a hoist button 21 for instructing a hoist and a lower button 22 for instructing a hoist.
And an operation setting volume 23 are provided.

In this prior art, for example, it is assumed that the operation speed of the induction motor 4 is set to be equivalent to 6 Hz by the speed setting volume 23 of the operation panel 20, and at this time, the hoist button 21 of the operation panel 20 is pressed. Then, an operation command 30 whose operation direction is “up” and whose fundamental frequency is “6 Hz” is output from the operation panel 20 to the control circuit 10. The control circuit 10 selects a preset 7 Hz frequency command value in response to the operation command 30, and gives this to the inverter circuit 7 as an operation command 31. Note that the frequency of 7 Hz is an example, and when the rated load is hoisted, the induction motor 4 slips due to insufficient torque, and
It is a frequency that rotates at the frequency of Hz. Inverter circuit 7
Supplies the power of the output frequency of 7 Hz corresponding to the given operation command 31 to the induction motor 4 and simultaneously releases the brake 6. As a result, a rotating magnetic field equivalent to 7 Hz is formed in the stator of the induction motor 4, but the rotor rotates at about 6 Hz due to slip.

If the operator presses the lower button 22 on the operation panel 20, an operation command 30 indicating that the operation direction is "down" and the fundamental frequency is "6 Hz" is issued from the operation panel 20.
Is output to the control circuit 10. The control circuit 10 selects a preset frequency command value of 5 Hz in response to the operation command 30, and gives this to the inverter circuit 7 as an operation command 31. The frequency of 5 Hz is, for example, a frequency at which the induction motor 4 slips in the negative direction due to insufficient torque when the rated load is lowered, and rotates at about 6 Hz. The inverter circuit 7 supplies electric power of an output frequency of 5 Hz corresponding to the given operation command 31 to the induction motor 4 and simultaneously releases the brake 6. As a result, a rotating magnetic field corresponding to 5 Hz is formed in the stator of the induction motor 4, but the rotor rotates at 6 Hz due to slip in the negative direction.

[0007]

In the above prior art,
Since the slip of the induction motor with respect to the rated load is considered, there is little difference in speed between the time of hoisting and lowering.However, for light load, the slip of the induction motor is reduced, so when winding up and lowering Causes a large difference in speed. Further, even in the operation in the same direction, the slip of the induction motor changes due to the difference in the load, so that the speed changes according to the load. In this way, if the speed changes according to the load, for example, when two hoists are used and the hanging operation is performed, if the load is unbalanced, the speed difference between the two units will be different. This causes the suspended load to tilt.

That is, in the prior art, the difference in load
There is a problem that the hoisting or lowering speed is different. Furthermore, in the prior art, there is also a problem that adjustment for each device is required to determine each speed, which is very troublesome.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a V / F control inverter-driven hoist capable of operating at a fixed speed without any particular adjustment and without being affected by a load.

[0010]

A V / F control inverter-driven hoist for achieving the above object comprises an induction motor for performing hoisting and lowering operations, and electric power of various output frequencies to the induction motor. A V / F control inverter-driven hoist comprising:
A basic frequency output unit that outputs a basic frequency predetermined according to an operating speed of the hoisting or lowering desired by the operator to the inverter circuit as a command value of the output frequency, and the induction motor is activated. An operation stability grasping means for grasping an operation stable state in which the acceleration is completed and the operation speed is considered to be stable, a rotation speed detecting means for detecting an actual rotation speed of the induction motor, and the operation stability grasping means. When the operation stable state is grasped, a deviation between the synchronous rotational speed of the induction motor corresponding to the fundamental frequency and the actual rotational speed detected by the rotational speed detecting means is determined, and a correction frequency at which the deviation is eliminated And output to the inverter circuit as a command value of the output frequency.

In the above-mentioned V / F control inverter driven hoist, the operation stability grasping means includes an output frequency detecting means for detecting the output frequency from the inverter circuit, and an output frequency detecting means for detecting the output frequency. Output / fundamental frequency comparison means for determining that the operation becomes stable when the output frequency becomes the same as the fundamental frequency. In addition, the operation stability grasping means may be configured to enter the operation stable state when the amount of change per unit time of the actual rotation speed of the induction motor detected by the rotation speed detection device becomes equal to or less than a predetermined value. It may have actual rotation speed stability determination means. further,
The operation stability comprehension means may include a stabilization time measurement means for measuring a predetermined stabilization time from when the induction motor is started to when the operation stabilization state is assumed. Good.

In one of the above-described V / F control inverter driven hoisting machines, the correction frequency output means includes:
When the deviation between the synchronous rotational speed of the induction motor corresponding to the fundamental frequency and the actual rotational speed detected by the rotational speed detecting means exceeds a normal deviation range predetermined for the fundamental frequency, It may output a stop command of the induction motive to the inverter circuit.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a V / F control inverter driven hoist according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the V / F control inverter-driven hoist of this embodiment has a load block 1, wires 2, a drum 3, an induction motor 4, a speed reducer 5, and a brake 6, as in the prior art. , An inverter circuit 7, a control circuit 10a, and an operation panel 20. Furthermore, in the present embodiment, an encoder that detects the actual rotation speed of the induction motor 4
It has a (rotational speed detecting means) 8 and a frequency detector (output frequency detecting means) 9 for detecting an output frequency of electric power supplied from the inverter circuit 7 to the induction motor 7.

The control circuit 10a includes a fundamental frequency output unit 13 for outputting a fundamental frequency corresponding to the operation speed of the induction motor 4 included in the operation command 30 from the operation panel 20,
An output / basic frequency comparing unit 15 for comparing the output frequency from the inverter circuit 7 detected by the output frequency detector 9 with the basic frequency, and a correction frequency based on the actual rotation speed of the induction motor 4 detected by the encoder 8 And a peripheral control unit 1 for controlling brakes and the like.
2 and a main control unit 16 for controlling these. An operation command 31a from the control circuit 10a to the inverter circuit 7 includes a start-up signal output from the peripheral control unit 12.
It includes a stop command 32, a basic frequency command 33 output from the basic frequency output unit 13, a correction frequency command 34 output from the correction frequency output unit 14, a rotation direction of the induction motor 4, and the like.

When the winding button 21 or the winding button 22 is pressed, the operation panel 20 outputs an operation command 30 to the control circuit 10a. Turning on the hoist button 21 and the lower button 22 means starting at the operating speed of the induction motor 4 set by the speed setting volume 23, and turning off these buttons 21 and 22 means stopping. I have. Therefore, the operation command 30 includes start / stop, hoisting / lowering, operating speed of the induction motor 4, and the like.

Next, the processing operation of the control circuit 10a of the V / F control inverter driven hoist of this embodiment will be described with reference to FIG.
This will be described according to the flowchart of FIG.

The main controller 16 of the control circuit 10 determines whether or not the operation command 30 has been input (step 1). If the operation command 30 has not been input, it waits until it is input. Then, go to step 2. In step 2, the main control unit 16 determines whether the operation command 30 includes information of “start” or “stop”. If the operation command 30 includes “stop”, the process proceeds to step 3, where the peripheral control unit A stop command 32 is transmitted from 12 to the inverter circuit 7. The inverter circuit 7 cuts off power supply to the induction motor 4 and the brake 6, and the brake 6 applies a braking force to the induction motor 4. If it is determined in step 2 that the operation command 30 includes the information of “start”, the process proceeds to step 4 where the correction frequency output unit 14 outputs a correction frequency command 34 to the inverter circuit 7. It is determined whether or not the command has been transmitted. If the correction frequency command 34 has been transmitted, the process waits until the operation command 30 is input again. If the correction frequency command 34 has not been transmitted, the process proceeds to step 5.

In step 5, the fundamental frequency output unit 13 sends a fundamental frequency command 33 to the inverter circuit 7, and the peripheral control unit 12 sends a start command 32 to the inverter circuit 7.
Send When the inverter circuit 7 receives the start command 32 together with the basic frequency command 33, it supplies power to the brake 6 to open the induction motor 4 so as to be drivable and to generate power of the same frequency (output frequency) as the basic frequency. 4

Here, for simplification of the following description, the operating speed of the 4-pole induction motor 4 is set to 6 Hz equivalent by the speed setting volume 23 of the operation panel 20. It is assumed that the hoist button 21 of the operation panel 20 is pressed. Then, of the above processing, step 1,
Steps 2, 4, and 5 are executed. In step 5, a 6 Hz basic frequency command 33 and a start command 32 corresponding to the operation speed (equivalent to 6 Hz) included in the operation command 30 are transmitted to the inverter circuit 7,
As shown in FIG. 3A, the brake 6 releases the induction motor 4, and the induction motor 4 starts to be driven.

In step 6, the output / basic frequency comparing section 15 outputs the frequency detected by the frequency detector 9, that is,
It is determined whether or not the output frequency of the power supplied from the inverter circuit 7 to the induction motor 4 matches the basic frequency. If the output frequency has not reached the fundamental frequency,
Assuming that the induction motor 4 is still accelerating, the apparatus waits until the output frequency matches the fundamental frequency. When the output frequency matches the fundamental frequency, it is determined that the acceleration has ended and the operation has been stabilized, and the process proceeds to step 7. This stable operation state is shown in FIG.
In the A region of (a), the induction motor 4 is stable at 150 rpm.

In step 7, the correction frequency output unit 14
Calculates the deviation between the synchronous rotation speed with respect to the fundamental frequency and the actual rotation speed of the induction motor 4 detected by the encoder 8.

More specifically, the synchronous rotation speed for a fundamental frequency of 6 Hz is (120 × 6 Hz) / 4 poles = 180 rpm.

Since the actual rotation speed detected by the encoder 8 is 150 rpm, the deviation between the synchronous rotation speed and the actual rotation speed is 180 rpm-150 rpm = 30 rpm. The deviation between the synchronous rotational speed and the actual rotational speed occurs because the induction motor 4 is slipping.

When determining the deviation between the synchronous rotation speed and the actual rotation speed, the correction frequency output unit 14 determines in step 8 whether the deviation is within a normal range. This normal deviation range is determined for each fundamental frequency. For example, when the fundamental frequency is 6 Hz, the normal range is a synchronous rotation speed corresponding to +1 Hz to -6 Hz, that is, +30 rpm to -180 rpm. When the fundamental frequency is 12 Hz, +1
Hz to -12 Hz, that is, + 30r
pm to -360 rpm is a normal range. If the deviation is not within the normal range, the process proceeds to step 10, where the correction frequency output unit 14 transmits a stop command 32 to the inverter circuit 7 via the peripheral control unit 12, and stops the induction motor 4. In this example, the deviation when the fundamental frequency is 6 Hz is + 30r.
pm, the deviation is within the normal deviation range (+30 rpm to -180 rpm) determined with respect to this fundamental frequency.

In step 9, the correction frequency output section 14 obtains a correction frequency 34 such that the deviation becomes zero, and transmits this to the inverter circuit 7.

Specifically, first, the frequency corresponding to the deviation of 30 rpm is calculated backward as follows.

(4 poles × 30 rpm) / 120 = 1 Hz Then, a basic frequency of 6 Hz is added to the frequency of 1 Hz to obtain a correction frequency of 7 Hz as follows.

6 Hz + 1 Hz = 7 Hz The obtained correction frequency of 7 Hz is transmitted to the inverter circuit 7, and as shown in FIG. 3A, the induction transmitter 4 accelerates from the actual rotation speed of 150 rpm, and synchronizes with the fundamental frequency of 6 Hz. The rotation speed is 180 rpm (B region in FIG. 7A) which is the same as the rotation speed.

In this embodiment, as can be understood from the processing in step 4, once the correction frequency command 34 is transmitted, the correction frequency is not transmitted again until a new operation command 30 is input. .

Next, the operation speed of the 4-pole induction motor 4 is set to 6 Hz or equivalent by the speed setting volume 23 of the operation panel 20.
The case where the lower button 22 is pressed will be described. In this case, just as when the hoist button 21 is pressed, the control circuit 10 executes the processing of steps 1, 2, 4, and 5, and the induction motor 4 operates in exactly the same manner. However, in the case of unwinding, the slip of the induction motor 4 becomes negative. Therefore, when it is determined in step 6 that the fundamental frequency and the output frequency match, that is, the operation of the induction motor 4 is stabilized (FIG. 3B). The actual rotation speed at the time of (C region) becomes 210 rpm.

In step 7, the correction frequency output unit 14
Is the synchronous rotation speed 180 rpm for the fundamental frequency 6 Hz.
And the actual rotation speed 210 rpm detected by the encoder 8 is determined as follows.

180 rpm−210 rpm = −30 rpm Since this deviation −30 rpm is within the normal deviation range (+30 rpm to −180 rpm) for the basic rotation speed of 6 Hz, the process proceeds to step 9 via step 8.

In step 9, first, the deviation (-) 30 rp
The frequency corresponding to m is calculated backward as follows.

(4 poles × (−30 rpm)) / 120 = −1 Hz Then, a fundamental frequency of 6 Hz is added to this frequency (−) of 1 Hz to obtain a correction frequency of 5 Hz.

6 Hz + (−) 1 Hz = 5 Hz The obtained correction frequency of 5 Hz is transmitted to the inverter circuit 7, and as shown in FIG. 3 (b), the induction transmitter 4 decelerates from the actual rotation speed 210 rpm. The rotation speed is 180 rpm (D region in FIG. 4B), which is the same as the synchronous rotation speed for a frequency of 6 Hz.

As described above, in this embodiment, the induction motor 4 is controlled so that the synchronous rotation speed with respect to the fundamental frequency and the actual rotation speed coincide with each other. Even if the load changes, the motor will actually rotate at the synchronous rotation speed with respect to the fundamental frequency corresponding to the operation speed included in the operation command 30.

The correction processing of the fundamental frequency as described above is effective not only when the fundamental frequency is 6 Hz, but also for all the velocities in a low-speed region where the output torque is hardly generated. In addition, it is necessary for safety that a frequency at which a load can be held at least is provided as a lower limit value for the correction frequency.

In the above embodiment, the operation stability grasping means is constituted by including the frequency detector 9 and the output / basic frequency comparing section 15. However, this operation stability grasping means is, for example, shown in FIG. 5 may be adopted.

That is, as shown in FIG. 4, when the change per unit time of the actual rotation speed of the induction motor 4 detected by the encoder 8 becomes equal to or less than a predetermined value as shown in FIG. It may be configured by the actual rotation speed stability determination unit 16 that assumes that the state has been reached.

As shown in FIG. 5, the operation stability grasping means measures a predetermined stabilization time from when the induction motor 4 is started to when it is assumed that the operation becomes stable. A time measuring unit (timer) 17 may be used.

[0042]

According to the present invention, the induction motor is controlled so that the synchronous rotation speed with respect to the fundamental frequency and the actual rotation speed coincide with each other. Even if the load changes, the motor actually rotates at the synchronous speed with respect to the basic frequency corresponding to the operation speed specified as the operation command. Therefore, in the hanging operation by the two vehicles, the inclination of the suspended load due to the imbalance of the load can be prevented, and the safety can be improved. Further, it is not necessary to make a troublesome speed adjustment for each device.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a V / F control inverter-driven hoist according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a processing operation of a control circuit according to an embodiment of the present invention.

FIG. 3 is a time chart of a V / F control inverter driven hoist according to an embodiment of the present invention.

FIG. 4 is a functional block diagram of a control circuit according to another embodiment of the present invention.

FIG. 5 is a functional block diagram of a control circuit according to still another embodiment of the present invention.

FIG. 6 is a functional block diagram of a conventional V / F control inverter driven hoist.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Road block, 2 ... Wire, 3 ... Drum, 4 ... Induction motor, 5 ... Reduction gear, 6 ... Brake, 7 ... Inverter circuit, 8 ... Encoder, 9 ... Frequency detector, 10, 10
a, 10b, 10c: control circuit, 13: fundamental frequency output unit, 14: correction frequency output unit, 15: output / basic frequency comparison unit, 16: actual rotation speed stability determination unit, 17: stabilization time measurement unit, 20 ... operation panel, 21 ... hoist button, 22 ...
Lowering button, 23: operation setting volume, 30: operation command, 31, 31a: operation command, 32: start / stop command,
33: basic frequency command, 34: correction frequency command.

Claims (5)

[Claims] 1. A V / F control inverter-driven hoist comprising an induction motor for performing a hoisting and lowering operation and an inverter circuit for supplying electric power of various output frequencies to the induction motor. Basic frequency output means for outputting to the inverter circuit a basic frequency predetermined according to the operating speed of hoisting or lowering desired by the user as the command value of the output frequency, and after the induction motor is started. Operation stability grasping means for grasping an operation stable state in which the acceleration is completed and the operation speed is considered to be stable; rotation speed detecting means for detecting an actual rotation speed of the induction motor; When the operation stable state is grasped, the deviation between the synchronous rotation speed of the induction motor corresponding to the fundamental frequency and the actual rotation speed detected by the rotation speed detecting means is determined. V / F control inverter-driven hoisting machine, comprising: a correction frequency output unit that obtains a difference and outputs a correction frequency that eliminates the deviation as a command value of the output frequency to the inverter circuit. 2. The V / F control inverter-driven hoist according to claim 1, wherein the operation stability grasping means includes an output frequency detecting means for detecting the output frequency from the inverter circuit, and an output frequency detecting means for detecting the output frequency. A V / F control inverter driven hoist comprising: output / fundamental frequency comparison means for determining that the operation becomes stable when the output frequency detected by the means becomes equal to the fundamental frequency. 3. The V / F control inverter-driven hoist according to claim 1, wherein the operation stability grasping unit is configured to detect the actual rotation speed of the induction motor per unit time detected by the rotation speed detection unit. A V / F control inverter-driven hoist comprising: an actual rotation speed stability determination unit that determines that the operation becomes stable when the amount of change becomes equal to or less than a predetermined value. 4. The V / F control inverter-driven hoist according to claim 1, wherein the operation stability grasping means is configured to operate after the start of the induction motor until the operation is assumed to be in the stable state. A V / F control inverter driven hoist comprising stabilization time measuring means for measuring a predetermined stabilization time. 5. The V / F control inverter-driven hoist according to claim 1, wherein said correction frequency output means includes a synchronous rotation speed of said induction motor corresponding to said fundamental frequency and said rotation speed. When the deviation from the actual rotation speed detected by the number detection means exceeds a predetermined normal deviation range with respect to the fundamental frequency, outputting a stop command of the induction motor to the inverter circuit. Characteristic V / F control inverter driven hoist.