JPH06255990A - Inverter controlled hoist - Google Patents

Abstract

PURPOSE:To provide the same function as a crab crane by driving a hoisting motor of a large capacity hoist by means of an iverter. CONSTITUTION:An operation push-button switch 2 is made up of a double action switch and a light-load changeover switch 3, and a hoisting motor 10 is operated at low speed by the first stage of the double actions, and is operated at the rated speed by the action of the second stage; and also it is enabled to be changed over to high-speed operation by means of a light-load speed-up changeover switch 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hoist for controlling a hoisting / lowering motor with an inverter, and more particularly to a large capacity hoist.

[0002]

2. Description of the Related Art A large capacity hoist having a rated load of 35 tons or more is required to have characteristics equivalent to those of a club crane. That is, the rotation speed of the hoisting motor is required to have a wide range of variable law operation from 0 to the rated speed and high torque in the low speed region.

Therefore, conventionally, like the club crane,
A DC electric motor is used as the hoisting electric motor depending on the hoisting load and the use place and the like, and the wording control method and the thyristor Leonard control method are used for control.

When a winding type induction motor is used as a hoisting motor, a secondary adjusting resistor is used for starting the motor, and the primary winding is directly connected to a power source with a maximum resistance value. ing.

In recent years, the use of thyristor inverters has become widespread in various fields. For hoists and small-capacity ones, a hoisting electric motor uses a robust and durable AC electric motor to control the output frequency of the inverter. Then, the method of controlling the number of times of the hoisting motor and varying the hoisting speed has been adopted. FIG. 5 is a schematic connection diagram of a general hoist under such inverter control.

In FIG. 5, reference numeral 10 is a hoist hoisting and hoisting motor (hereinafter simply referred to as a motor), 11 is an inverter, and a forward conversion unit CO for converting the electric power of the three-phase AC power source E into DC. An inverse conversion unit IV that converts the DC output of the forward conversion unit CO into an AC, a smoothing capacitor C, a base drive circuit that controls the output voltage and frequency by controlling the base of the inverse conversion unit IV, and an operation push button. The control circuit CS is configured to control the sequence of winding and lowering the motor 10 by operating the switch 12. The operation push button switch 12 is a button switch 12 for winding and winding.
U and 12D, and the button switches 12U and 12D have high-speed hoist and high-speed hoist switches UH and DH, and rated speed hoist and rated speed hoist switches UR and DR, respectively. The operation push button switch 12
Other than the above, a push button switch for left and right operation and the like is provided, but it is omitted. Reference numeral 13 is an electromagnetic switch, which is a contact point 1 for hoisting.
3U and unwinding contact 13D, provided between the inverter 11 and the motor 10, and these contact points 13U, 13D
Is closed when the hoisting and lowering button switches 12U and 12D of the operation push button switch 12 are pressed to switch the rotation direction of the motor 10. In addition, this electromagnetic switch 1
3 is not necessary when the phase order of the output voltage is changed by the control of the inverter 11. Reference numeral 14 denotes a brake operation circuit, which takes out two phases from the three-phase AC power source E, half-wave rectifies them with the diodes D ₁ and D ₂ through the brake contacts CU and CD, and connects them to the brake trip coil of the electromagnetic brake MB. There is. These contacts CU and CD are electromagnetic switches 13
When the hoisting or lowering contact 13U or 13D is closed, it is closed and released to close the brake.

In a hoist controlled by an inverter (hereinafter abbreviated as "inverter hoist"), the speed of the motor can be controlled arbitrarily, so that the hoisting or unwinding control can be performed at high speed when there is no load in order to improve the efficiency of the work of moving the load. Is being done. The operation is performed by pressing the high-speed hoisting or high-speed hoisting switch UH or DH of the operation push button switch 12. To operate the high-speed hoist (lower) switch UH or DH, when the operator sees a load sensor (not shown) attached to the hoist and determines that there is no load, he pushes the push button. 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.

[0008]

The hoist with invar control can be applied to a hoist having a small rated load without any problem, but hoisting and hoisting of a large capacity hoist having a rated load of 35 tons or more can be performed by an inverter. In the case of controlled operation, various problems occur and it cannot be easily applied. Especially when a function equivalent to that of a club crane is required, it is possible to control a wide range of speeds, and is ideal for improving work efficiency under conditions with a large lifting load and a long hoisting lift. The problem is how to set the hoisting and lowering speeds. Conventionally, a mechanical load detector is used to achieve high speed at no load. In this case, however, a load detector is required, and if this load detector is attached, the hoist hook will be moved from below the hoist I-beam. However, there is a problem that the distance to be increased and the range for carrying the suspended load is narrowed.

When controlling a large-capacity hoist with an inverter, the capacity of the inverter is naturally large, but in this case, a smoothing capacitor is provided on the input side of the inverse conversion section in the inverter. Because it is provided,
A predetermined time is required until the capacitor is charged after the power is turned on, and if the push button switch is pressed to operate the inverter before the capacitor is charged, the protection function of the inverter trips and the operation becomes impossible. This charging time is not a problem in the case of a small capacity inverter, but it is a problem because it is large capacity and the operator of the hoist operates the push button switch without considering the charging time at all.

Furthermore, the inverter is provided with a protection function, and during hoist operation, the protection function may be activated due to a failure or overcurrent, and the inverter may stop.

After the operation of the inverter is stopped, in order to restart the operation of the inverter hoist, the power source must be cut off or reset. Normally, the push button switch for operation is
Since there is no push-button for turning the power on and off, when turning off the power, you have to go to the power supply station (often installed in the corner of the building), turn off the power, and then turn it on again. There is a problem that the efficiency is significantly reduced.

Therefore, an object of the present invention is to solve the above various problems and to realize a large capacity inverter hoist.

[0013]

Means for solving the above-mentioned problems in the present invention is to connect a hoist hoisting and hoisting motor to the output side of an inverter and hoist it by operating an operating push button switch. In a hoist adapted to perform lowering switching and speed control of a motor, the operation push button switch is composed of a two-step action switch and a light load speed-up changeover switch, and a first-step action of the two-step action push button switch. The low speed operation and the rated speed operation are performed by the second action, and the speed setting is switched to high speed by turning on the light load speed up changeover switch.

Further, the operation push button switch is composed of a two-stage action push button switch, and the first stage action is for low speed operation and the second stage action is for rated speed operation, and the output current of the inverter is detected. Then, the detected current value is compared with a preset no-load current value, and when the detected current value is smaller than the set value, it is judged as no load and the speed is close to twice the rated speed. Determines that there is a load and operates at rated speed.

Further, the power supply circuit in the control circuit of the inverter is provided with a contact which is closed when the capacitor charging of the inverter is completed.

Further, the lowering button switch of the operation push button switch is provided with a timer which operates when the switch is closed, and the output contact of the timer resets the protection function of the inverter. Characterize.

[0017]

Since the present invention is constructed as described above, the low speed hoisting (lowering) operation of the hoist is performed by the action of the first step of the operation push button switch, and then the rated speed is performed by the action of the second step. Winding (lowering) is performed. In the invention of claim 1, the speed is further increased by operating the light load speed-up changeover switch.

According to the second aspect of the invention, the output current of the inverter is detected, and when the detected current value becomes equal to or less than the no-load set value, the operation is performed at a speed twice the rated speed. It is automatically selected for speed operation.

Further, in the invention of claim 3, even if the operator of the inverter hoist presses the operation push button switch before the charging of the smoothing capacitor is completed, the power supply is not connected to the control circuit, and the inverter is started only after the charging is completed. Can be controlled.

Further, according to the invention of claim 4, when the protection function of the inverter operates and trips, the timer operates by pressing the low speed lowering switch, and the protection function is provided at the output contact. Reset.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings.

FIG. 1 is an explanatory view of an inverter and an operation push button switch portion according to an embodiment of the present invention. Note that, except for the control circuit and the push button switch for operation, it is functionally the same as that of FIG. Further, parts having the same names as those in FIG. 5 are assigned the same reference numerals as those in FIG.

In FIG. 1, reference numeral 1 denotes an inverter, which comprises an inverter circuit 1a and an inverter control circuit 1b for performing sequence control. The inverter circuit 1a is not shown in the drawing, but in the same manner as in FIG. A conversion part,
It is composed of an inverse converter for converting the rectified DC power into an AC of an arbitrary frequency and a smoothing capacitor. Reference numeral 2 denotes an operation push button switch, which has a hoisting button switch 2∪ and a hoisting button switch 2D. Each of these button switches 2∪ and 2D is a two-step action push button switch,
It is normally open, and the contact 21 for low speed is closed in the first action, and the contact 22 for rated speed is closed in the second action. Reference numerals 23 and 24 denote interlocking contacts, for example, when the hoisting button switch 2∪ is pressed, the contact 24 is opened and the circuit on the lowering button switch 2D side is opened.

Further, the inverter drive circuit in the control circuit 1 includes the hoisting and lowering button switches 2∪ and 2D.
When the contact 21 for low speed is closed by the action of the stage,
Set the output frequency of the inverter 1 is, for example, 6H _Z (1/10 of the rated frequency), without the motor 10 to the low-speed operation of 1/10 of rated speed, and in the action of the second stage When the contact 22 for rated speed is closed,
And the output frequency 60H _Z set to operate the motor at rated speed. Reference numeral 3 denotes a light load speed-up changeover switch provided on the operation push button switch 2. When the changeover switch 3 is closed, the relay R operates and its output contact Rx.
Is closed and the terminals P ₁ and Ryo are short-circuited to switch the speed setting to the high speed side.

In FIG. 1, FR indicates a signal terminal for forward rotation and RR indicates a signal terminal for reverse rotation.

Next, the operation will be described. During normal operation, when hoisting a hoisted load, operate the hoist button switch 2∪ to close the low speed contact 21 in the first action to operate at low speed, then press the push button further. The contact 22 for rated speed is closed in the second stage action to perform hoisting operation at the rated speed. However, if the suspended load is light load or no load during operation, operate the light load speed up changeover switch 3. Close. At that time, the rated speed setting is switched to the high speed side, and the hoisting or lowering speed becomes high.

In the embodiment of FIG. 1, when switching to high speed operation at light load, the degree of light load is determined by the operator's judgment, but it is automatically switched to high speed operation at light load or no load. May be requested. Conventionally, a method has been adopted in which a mechanical load detector is provided and switching is performed by the output signal of this detector, but this method has a problem that the carrying range of the suspended load is narrowed as described above. It was Therefore, the present invention is intended to switch at high speed without a load without using a mechanical load detector.

FIG. 2 shows a second embodiment of the present invention, in which the output current of the inverter 1 (input current of the motor 1) is detected by the current detector 4.
When the detected current value is a predetermined value, that is, the switching set value K or less, the contact x is closed as in the case of FIG. 1 to set the rated speed to the high speed side, for example, the rated speed. Set to double speed and switch. That is, for example, in the case of hoisting, when the hoisting button switch 2∪ is pressed and the low speed contact 21 is closed by the action of the first step, the hoisting motor 10 is operated at low speed. Since the current I flowing through the motor 10 at this low speed is close to the rated current and is larger than the switching set value K, it cannot be switched to the high speed side. When the contact 22 is closed and accelerated by the action of the second step and the detected current value I becomes equal to or lower than the switching set value K, it is determined that there is no load, and the contact x for high speed switching is closed to double the rated speed. It will be driving. Also, K
In the case of <I, it is determined that there is a load, and the rated speed operation is performed.

This control method can be used for a crane having a long traveling distance when the traveling motor is operated by the inverter device.

FIG. 3 shows a third embodiment of the present invention, in which a start-up or a protective function of the inverter, which is a problem when controlling hoisting and lowering of a large capacity hoist by the inverter 1, operates. Regarding resetting when stopped.

In this embodiment, a capacitor C in the inverter 1 (see FIG. 5) is used in the power supply circuit of the control circuit 1b.
A contact SON is provided that closes when charging is completed. A smoothing capacitor C is provided in the DC circuit between the forward converter and the inverse converter in the inverter 1, and the inverter 1 can be operated only after the charging of the capacitor C is completed.

The charging time is not a problem for an inverter hoist having a small capacity, but it takes about 5 to 6 seconds for a large (large capacity) inverter hoist, and the operation button switch 2 is pushed before charging is completed. And the protection function of the inverter trips and it becomes impossible to operate.

The inverter generally has an initial charging circuit, and after the power is turned on and the charging is completed, the switch MC (FIG. 5) provided in the DC circuit between the forward conversion section and the reverse conversion section is turned on. As the contact SON, a contact of a sequence circuit (servo circuit) that operates the switch SON is used. Therefore, unless the charging of the capacitor is completed, the control circuit cannot operate and therefore does not trip. In addition, contact SON
May be provided with a relay that operates by detecting the voltage across the capacitor C, and may be used as its output contact.

Reference numeral T in FIG. 3 denotes a timer, which is connected in series with the low speed contact 21 of the lowering button switch 2D, and resets the protection function at the timer output contact Tx. The control circuit of the inverter has a base drive circuit for the inverse conversion unit, and this base drive circuit has a protection circuit that trips or resets the base drive circuit by detecting overcurrent etc. It is something to send.

FIG. 4 is an explanatory diagram of the operation sequence, and when the protective function of the inverter operates, when the lowering button switch 2D is pressed and the first-stage contact 21 is closed, the timer T operates and the contact Tx is turned on. Closes after a predetermined time and resets the protection function. This reset (performed by a one-shot signal) causes the hoist to be lowered.

When the protection function of the inverter operates during the operation of the inverter hoist, it is almost always caused by overcurrent when winding by overload, and therefore the purpose can be achieved by using the lowering button switch. Further, the reset is reset by a one-shot signal. Therefore, even when the protection function operates, the work can be continued without shutting off the power.

In FIG. 3, the contact SON is closed to connect the power source to the control circuit 1b after the charging of the capacitor is completed. However, the contact SON is not always necessary for the reset circuit, and is indicated by the dotted line. As shown in, the power supply may be directly connected without passing through the contact SON.

[0038]

As described above, according to the first aspect of the present invention, the operation switch is provided with the two-step action push button switch and the light load speed up changeover switch for switching at high speed at light load. Low-speed (for example, 1/10 of rated speed) hoisting (lowering) with 1-step action and 2-step action, hoisting (lowering) at rated speed, and high-speed hoisting (lowering) with light load speed up changeover switch at light load Therefore, even if the hoisting height is long due to heavy load, the large-capacity inverter hoist can change the speed in the same manner as the hoisting machine of a club crane, and work efficiency can be further improved.

According to the second aspect of the invention, the load current of the inverter is detected without using a mechanical load detector, and the no-load or the loaded state is judged by the detected current to determine the high speed ( (Double speed) or rated speed operation is automatically selected to operate, so in addition to improving work efficiency, the range for carrying suspended loads is not pinched, so there is no need to change the standard hoist size, The usage space does not change.

According to the third aspect of the present invention, the control circuit of the inverter is not connected to the power source unless the charge completion signal of the inverter is output, so that the operator does not have to worry about the charging time of the capacitor. Also, even if the operation push button switch is operated before the charging is completed, there is no trip, so that the operation can be performed with peace of mind.

Further, according to the invention of claim 4, even if the protection function of the inverter operates and trips, the protection function is reset by the action of the first step of the lowering button switch. Therefore, it is possible to save various troubles such as shutting off and re-entering, and continuing the work.

[Brief description of drawings]

FIG. 1 is an operation explanatory diagram of an inverter and an operation push button switch according to a first embodiment of the present invention.

FIG. 2 is an operation explanatory view of an inverter and an operation push button switch according to a second embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of an inverter and an operation push button switch according to a third embodiment of the present invention.

FIG. 4 is an operation procedure explanatory diagram of the third embodiment of the present invention.

FIG. 5 is a schematic wiring diagram of a conventional hoist controlled by an inverter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inverter 2 ... Push button switch for operation 2 ∪ ... Button switch for hoisting 2D ... Button switch for hoisting 21 ... Contact for low speed 22 ... Contact for rated speed 23 ... Contact for interlock 24 ... Contact for interlock 3 ... Light load speed up changeover switch 4 ... Current detector T ... Timer

Claims (4)

[Claims] 1. A hoist in which a hoist hoisting / lowering motor is connected to an output side of an inverter, and hoisting / lowering switching and motor speed control are performed by operating a push button switch for operation. The operation push button switch is composed of a two-step action switch and a light load speed-up changeover switch. The first-step action of the two-step action push-button switch allows low-speed operation and the second-step action achieves rated speed operation. Inverter-controlled hoist characterized in that the speed setting is switched to high speed by turning on the load speed up switch. 2. A hoist in which a hoist hoisting / lowering motor is connected to an output side of an inverter, and hoisting / lowering switching and motor speed control are performed by operating a push button switch for operation. The operation push button switch is composed of a two-step action push button switch, the first step action is for low speed operation and the second step action is for rated speed operation, and the output current of the inverter is detected to detect the detected current value. Compares it with the preset no-load current value.If the detected current value is smaller than the set value, it is judged as no load and the speed is close to twice the rated speed.If it is larger than the set value, it is judged that there is a load. Inverter-controlled hoist characterized by operating at the rated speed. 3. The hoist according to claim 1 or 2, wherein the power supply circuit in the control circuit of the inverter is provided with a contact which is closed when the capacitor charging of the inverter is completed. 4. A push-down button switch of the operating push-button switch is provided with a timer that operates when the switch is closed, and the protection function of the inverter is reset by the output contact of the timer. The hoist controlled by the inverter according to claim 1 or 2 or 3.