JPH08127496A - Hoist through control of inverter - Google Patents

Abstract

PURPOSE: To facilitate setting of a high speed and a middle high speed during low load running by a method wherein an output current detecting signal from an inverter by a light transformer is used and upper and lower limit set values for controlling switching of an output frequency are set and compared with a detecting signal from the light transformer by a control circuit for an inverter to control winding up (winding down). CONSTITUTION: A light transformer, hereinafter abbreviated CT, detects a signal value proportioning the output current of an inverter IV and inputs it to a control circuit 3. The output frequency of the inverter forms a rated frequency and starting is effected at a rated speed. A current output current is detected by the light CT and compared with predetermined upper and lower limit set values. When the detecting signal is below the lower limit set value, the set frequency of the inverter is switched to, for example, 120Hz and high speed winding up (winding down). When it exceeds the lower limit set value, a rated speed is kept as it is and the set frequency is compared with the upper limit set value. When the set frequency is below the upper limit set value, it is decided that a load is an ordinary load and rated speed operation is continued. When it is below the upper limit set value, it is decided that the load is a light light and setting to a middle high speed is effected.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an inverter-controlled hoist.

[0002]

2. Description of the Related Art As a hoist hoisting, hoisting and traversing motor, an induction motor which is robust and has few failures is generally used. In recent years, an inverter whose frequency can be freely changed has become widespread, and has come to be used for speed control of a hoist motor. FIG. 3 shows a schematic connection diagram of a conventional hoist by such inverter control.

In FIG. 3, reference numeral 10 is a hoist hoisting / lowering motor (hereinafter simply referred to as a motor), 11 is an inverter section, which is a converter CO for converting the electric power of a three-phase AC power source E into DC. The inverter IV for exchanging the direct current output of the converter CO into an alternating current, the base drive circuit for controlling the output voltage and frequency by controlling the base of the inverter IV, and the operation push button switch 12 are operated to wind up and wind down the motor 10. It is composed of a control circuit CS for performing sequence control such as. The operation push button switch 12 has hoisting and hoisting button switches 12U and 12D, and these button switches 12U and 1D.
2D includes high-speed hoist and high-speed hoist switches UH and D, respectively.
H and low speed upper and lower speed switches UR and DR. In addition to the above, the operation push button switch 12 is provided with a push button switch for left and right traverse operation, etc., but is omitted. Reference numeral 13 denotes an electromagnetic switch, which is composed of a hoisting contact 13U and a hoisting contact 13D and is provided between the inverter unit 11 and the motor 10. These contacts 13U and 13D are used for hoisting and hoisting the operation push button switch 12. When the lower button switches 12U and 12D are pressed, they are closed, and the rotation direction of the motor 10 is switched. The electromagnetic switch 13 is not necessary when the phase order of the output voltage is changed by the control of the inverter unit 11. Reference numeral 14 is a brake operation circuit, which takes out two phases from the three-phase AC power supply E, and connects the brake contacts CU,
Half-wave rectification is performed by the diodes D ₁ and D ₂ via the CD, and is connected to the brake trip coil of the electromagnetic brake MB. The contacts CU and CD are opened and closed in conjunction with the electromagnetic switch 13, and when the hoisting or lowering contacts 13U or 13D are closed, the contacts are closed to release the brake.

By pressing the low speed hoist (lower) switch, the output frequency of the inverter unit 11 is set to, for example, 6 Hz (1/10 of the rated frequency), and the motor 10 is operated by the low speed command from this switch. At low speed and pressing the high-speed hoist (lower) switch,
z is set so that the motor 10 is driven at high speed by a high speed command from the high speed hoisting switch, and high speed hoisting (winding) is performed via the hoist winding drum.

In a hoist controlled by an inverter (hereinafter abbreviated as "inverter hoist"), the speed of the motor can be controlled arbitrarily. Therefore, in order to improve the efficiency of the work of moving the load, hoisting or unwinding control is performed at high speed under no load. Is being done. The operation is the push button switch 1 for operation
This is done by pressing the high-speed winding or high-speed lowering switch UH or DH of No.2. The operator operates the high-speed hoist (lower) switch UH or DH by pressing a push button when he / she sees a load sensor (not shown) attached to the hoist and determines that there is no load. When the high-speed hoist (lower) switch is pressed, the control circuit gives a control signal of a frequency higher than that during normal operation to the inverter, and the motor 10 is operated at high speed.
High-speed hoisting (lowering) is performed via a drum driven by the motor 10.

Further, when the operator presses the push button while visually observing the load sensor, the operator is burdened. Therefore, the load sensor determines the unloaded weight and automatically performs high-speed hoisting (lowering). Switching method, or as shown in FIG. 3, the output current of the inverter unit 11 is detected by the current transformer CT, this detection signal is input to the judgment circuit 15, and the judgment circuit 15 compares it with the set value to set the set value. In the following cases, it is determined that there is no load and the control circuit C
A method has also been proposed in which an output signal is output to S and the frequency is switched to perform high-speed operation.

[0007]

A load sensor is required when a mechanical load detecting means such as a load sensor is used to achieve high speed with no load, and when this load sensor is attached, the load sensor can be operated from below the I-beam of the hoist. The distance to the hook of the hoist becomes longer, and the range for carrying the suspended load is narrowed.

Further, in the method of detecting the load current, the current transformer CT and the judgment circuit are required, which must be incorporated in the control box attached to the hoist.
There is a problem that the shape of the control box becomes large.

In view of the above points, it is an object of the present invention to provide a hoist controlled by an inverter, which is capable of easily setting a high speed, a medium speed and a high speed at a light load without the need to provide a load sensor or a current transformer. And

[0010]

Means for Solving the Problems In the present invention, the means for solving the above-mentioned problems is to control the speed of a hoist hoisting and hoisting motor by frequency control of an inverter. In order to use the output current detection signal of the inverter by the optical CT introduced into the control circuit of the inverter in the hoist controlled by the inverter, the switching circuit controls the output frequency of the inverter. The upper limit set value and the lower limit set value of are set in advance, and the set value is compared with the detection signal of the optical CT,
High-speed hoisting (lowering) when the detection signal is below the lower limit set value
If none, lower limit set value or more, the rated speed is hoisted (lowered), and then compared with the upper limit set value. Is
The hoisting (lowering) control is performed at a medium to high speed higher than the rated speed, and the speed control corresponding to the suspended load is automatically performed by one operation push button switch to improve work efficiency.

[0011]

Since the present invention is constructed as described above,
When the hoist push button switch is pressed, the motor 10 starts at the rated speed. When the value of the detection signal detected by the optical CT is equal to or less than the preset lower limit setting value several seconds after the start-up, it is determined that there is no load, and the winding is performed at high speed.

If the value of the detection signal is higher than the lower limit set value, it means that the hoist is under load. Therefore, the hoist is operated at the rated speed and compared with the upper limit set value. For example, it is wound at the rated speed, and if it is less than the upper limit set value, it is judged as a light load and it is wound at a higher speed than the rated speed.

In the case of lowering, the same speed control is performed by pressing the lowering push button switch.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. FIG. 1 shows a schematic block connection diagram of an embodiment of an inverter section of the present invention, and an electromagnetic switch and a brake operating section are omitted. Note that the same reference numerals as those in FIG. 3 are given to the same names or corresponding portions, and the description thereof will be omitted.

In FIG. 1, reference numeral 1 is an inverter unit, and FIG.
Corresponding to the inverter unit 11. Reference numeral 2 denotes an operation push button switch, which has a hoisting push button switch 2U and a hoisting push button switch 2D, and is connected to the control circuit 3 of the inverter.
The control circuit 3 of the inverter generally has a control power supply section 31 for obtaining a DC voltage for control, a bus control section 32, a failure detection section 33, a base drive circuit section 34, and a storage circuit RA.
It is composed of an M, a ROM, an arithmetic circuit CPU, and a bus circuit 35 connecting these, and is mainly composed of an IC circuit.

Reference numeral 4 denotes an optical transformer (hereinafter, abbreviated as optical CT).
Then, a signal value proportional to the output current of the inverter IV is detected as a detection signal and input to the control circuit 3. This detection signal is used for overcurrent protection and current control.

The present invention is based on this already used optical CT.
Is used to control the output frequency of the inverter to control the rotation speed of the motor, that is, the hoist hoisting and hoisting speed.

FIG. 2 is an explanatory diagram of specifications to be written in the setting ROM for controlling the inverter output frequency of the control circuit 3. When the hoisting or lowering pushbutton switch 2U or 2D is pressed, the output frequency of the inverter is the rated frequency of 50 Hz.
(Or 60 Hz) to start at the rated speed, the output current of the inverter at this time is detected by optical CT (S1), and the detected detection signal (S2) is set to an upper limit setting value and a lower limit setting value. Introduced into (S3), determination unit (S4)
Compare with the lower limit setting value. When the detection signal is less than or equal to the lower limit set value, the set frequency of the inverter is set to 12
It is switched to 0 Hz for high speed winding (winding) (S5).

At this time, if the lower limit setting value or more,
The determination unit (S7) compares the upper limit set value with the rated speed (S6), and if the detection signal is equal to or higher than the upper limit set value,
It is judged as a normal load and the rated speed operation is continued (S
8).

When the detection signal is less than the upper limit set value, it is determined that the load is light and the speed is higher than the rated speed.
z) (S9).

It should be noted that the upper and lower limit set values and the frequency setting under no load and light load are appropriately set according to the hoist user's request, operating conditions, etc. When low speed is required, inverter setting is required. This can be easily done by reducing the frequency and writing this.

The means for switching the rotation direction of the motor 10 is not limited to the electromagnetic switch 13 as shown in FIG.
It is the same as the conventional case that the phase order of the output voltage may be changed by the control of the inverter unit 11.

The present invention can also be applied to hoisting, traversing and traveling of hoist cranes.

[0024]

As described above, according to the present invention, it is possible to easily set the high speed under no load and the high speed during light load by simply writing the specifications in the inverter setting ROM of the control circuit. Since the switch can automatically perform optimal speed control according to the load, work efficiency is dramatically improved.

Further, since there is no need for a current transformer or a determination circuit, the control box does not become large, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a schematic connection diagram of an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of an embodiment of the present invention.

FIG. 3 is a schematic wiring diagram of a conventional hoist controlled by an inverter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inverter section 2 ... Operation push button switch 2U ... Winding push button switch 2D ... Winding push button switch 3 ... Control circuit 4 ... Optical CT 10 ... Winding (winding) motor

Claims (1)

[Claims] 1. A hoist for hoisting and lowering a hoist, wherein speed is controlled by frequency control of an inverter, and this speed control is performed by operating a push button switch. Introduced into a control circuit of the inverter. The output current detection signal of the inverter by the optical CT is used, and the upper limit setting value and the lower limit setting value for switching control of the output frequency of the inverter are preset by the control circuit of the inverter. After comparing with the CT detection signal, if the detection signal is less than or equal to the lower limit setting value, it is determined as high-speed hoisting (lowering), and if it is more than the lower limit setting value, the rated speed hoisting (lowering) is performed. , Compared with the upper limit set value, if the upper limit set value or more, continue the rated speed, and if it is less than the upper limit set value, hoist at medium to high speed faster than the rated speed Hoist by inverter control, characterized in that to perform the control.