JPH032798B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a hoisting machine equipped with an overload protection means for a hoisting motor.

[Conventional technology]

Figure 1 shows a conventional device disclosed in, for example, Japanese Patent Publication No. 51-34179. A three-phase AC hoisting motor is connected to power supply cables r, s, and t via reversible electromagnetic contactors (to be described later), and CU is an electromagnetic contactor that is energized during hoisting operation of the motor _{M. 2} , Normally open main contact of CUa ₃ , normally closed auxiliary contact of CUb, and coil
CUc.

CD is an electromagnetic contactor that is energized during lowering operation of the electric motor M, and has normally open main contacts CDa ₁ , CDa ₂ , CDa ₃ , CDa ₄ , a normally closed auxiliary contact CDb, and a coil CDc. It is.

CT ₁ is a current detector that detects the current in cable t, and CC ₁ is a comparator H that compares and detects when the current input by CT ₁ has reached an overload state of a predetermined value or more, as detailed in Figure 2. ₁ and a holding circuit _K1 that maintains that the current input has reached a predetermined value or more based on the output _of the comparator _H1 . When this happens, the holding circuit _K1 is reset. RY is a relay that is energized when the holding circuit _K1 is energized (held) and has a normally closed contact RYb. Bu is a push button switch for winding up, and Bd is a push button switch for lowering.

Note that the normally open main contact CDa ₄ of the electromagnetic contactor CD is connected to the holding circuit K ₁ of the control circuit CC ₁ , and is mounted in a position separated from the control circuit CC ₁ formed on the board. A long lead wire (not shown) is routed from the electromagnetic contactor CD to the holding circuit _K1 .

In a device configured in this way, the switch
When Bu is turned on, CUc is energized and contact CUa ₁ ,
Since CUa ₂ and CUa ₃ are closed, motor M performs hoisting operation, and when switch Bu is turned off, hoisting operation is stopped. Also, if you turn on the switch Bd
CDc is energized and contacts CDa ₁ , CDa ₂ , CDa ₃ are closed, so motor M performs lowering operation and the switch is turned off.
If you turn off Bd, the lowering operation will stop. Also,
If overload operation occurs during hoisting operation, relay RY will be activated.
is energized, contact RYb is opened and continuation of hoisting operation is stopped, and contact CDa ₄ is opened by subsequent hoisting operation.
When the holding circuit K1 is closed, the holding circuit _K1 is reset and prepared for the next hoisting operation.

By the way, overload is detected by detecting the current in the cable t phase with a current detector CT ₁ and comparing the value with a reference value with a comparator H ₁ .
By the way, since the detected value of this current value also fluctuates due to fluctuations in the power supply voltage, it is necessary to correct this. A device with the following is disclosed. This reference voltage correction circuit aims to improve overload detection accuracy by correcting power supply voltage fluctuations.

[Problem that the invention seeks to solve]

Conventional hoisting devices such as those described above perform overload protection by detecting current with a current detector, and although compensation for power supply voltage fluctuations is implemented, the current value varies depending on the temperature of the motor. However, the detection accuracy is also limited. In particular, when the motor has a small capacity, the relationship between the current value and the load has a small amount of change as shown in Figure 5, and there is a problem that the influence of temperature changes on the motor is large, resulting in a decrease in detection accuracy. Ta. On the other hand, in order to restore the motor after it has been cut off due to overload, the holding circuit K ₁ is reset using the normally open main contact CDa ₄ of the magnetic contactor CD for lowering operation. Therefore, the lead wire of the normally open main contact CDa ₄ must be wired on the board of the control circuit CC ₁ , which not only complicates the wiring and lowers productivity, but also requires wiring of the lead wire of the normally open main contact CDa ₄ on the board of the control circuit CC 1. There was a problem in that an expensive contactor with many contacts was required.

[Means for solving problems]

The hoisting device according to the present invention includes a three-phase induction motor for hoisting, a reversible electromagnetic contactor that operates in response to hoisting and lowering operations of the motor, and a reversible electromagnetic contactor that is connected to the power supply side of the electromagnetic contactor and that is connected to the power supply side of the electromagnetic contactor. an operation switch that controls hoisting and hoisting operations; a voltage detector connected to the power supply side of the electromagnetic contactor to detect the power supply voltage; a current detector that detects the motor current flowing to the load side of the contactor; A power detector detects electric power based on the output of the voltage detector and the output of the current detector, and when the output of the power detector reaches an overload state value during hoisting operation of the motor, a first means for cutting off and holding the upper operation circuit; and a first means disposed on the same board as the first means, the output of the power detector being set to a value in the lowering state when the motor is in lowering operation; It is provided with a second means for restoring the above-mentioned cut-off state depending on a certain thing.

[Effect]

The first means of the hoisting device in this invention holds the hoisting operation circuit of the motor inactive when the motor reaches an overload state, and the second means maintains the hoisting operation circuit of the motor when the motor is in a lowering operation. is at the value of the lowered state, thereby recovering the above-mentioned shrunk state.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4. In the figure, TR ₁ , TR ₂
is a transformer that constitutes a voltage detector that detects the power supply voltage, CT ₂ is a current detector that detects the W-phase current of motor M, and CC ₂ is the voltage input from transformer TR ₂ as detailed in Fig. 4. and a current input by CT ₂ , and a comparator _{H 2 that} compares and detects that the detected power of the power detector Sp ₂ has reached an overload state of a predetermined value or more. , a holding circuit _K2 that maintains that the output of the power detector _Sp2 has reached a predetermined value or more based on the output of the comparator _H2 ;
This control circuit is formed on a substrate and includes a reset circuit Rs that detects the output of the power detector _Sp2 and resets the holding circuit _K2 when the electric motor M is in a lowering operation. In addition, explanations of other symbols are given in Part 1.
The explanation is the same as that of the figure and FIG. 2, so the explanation will be omitted.

In the device configured as above, when an overload operation occurs during hoisting operation, the power is output to the power detector Sp ₂ due to the voltage input from the transformer TR ₂ and the current input from the current detector CT ₂ . Detected.
Incidentally, the amount of work of the electric motor M is expressed as the product of the load W and the hoisting speed R, and this is proportional to the power detector _Sp2 . That is, W×R∝VI cosθ. Therefore, the power detector Sp ₂ detects a value corresponding to the amount of work, and detects overload with high accuracy.

As shown in FIG. 6, it is detected as the product P of voltage V and current I, and the current value corresponding to the waveform indicated by the broken line in the figure is output. When the comparator _H2 detects the overload state value _P3 shown in FIG. 7 by comparing the output voltage value of the power detector _SP2 and the internal well-known reference voltage I, the comparator H2 sets the voltage in the holding circuit _K2 . Send commands. When the well-known flip-flop in the holding circuit _K2 is set, its output keeps the relay RY energized, opening the contact RYb and stopping the motor M. By the way, when the lowering operation is performed, the power detector SP ₂ outputs a voltage value corresponding to the value P ₂ in the lowering state shown in FIG. By comparing the values, it is detected that the output of the power detector SP ₂ is at the lowering value, and the holding circuit K ₂ is reset, so that the relay RY is deenergized, the contact RYb is closed, and the next The winding operation becomes possible.

〔Effect of the invention〕

As described above, the present invention provides a hoisting three-phase induction motor, a reversible electromagnetic contactor that operates in response to the hoisting and hoisting operations of this motor, and a reversible electromagnetic contactor that is connected to the power supply side of the electromagnetic contactor, Upper, an operation switch for controlling hoisting and lowering operation; a voltage detector connected to the power supply side of the electromagnetic contactor to detect the power supply voltage; a current detector for detecting the motor current flowing to the load side of the contactor; A power detector supplies power from the output of the voltage detector and the output of the current detector, and when the output of the power detector reaches an overload state value during hoisting operation of the motor, hoisting of the motor is performed. a first means for breaking and holding the operating circuit;
and a second means disposed on the same board as the means for restoring the welded state when the output of the power detector is at a value corresponding to the lowering state during lowering operation of the motor. Therefore, the power detector detects a value that corresponds to the actual amount of work of the motor, which has the effect of greatly improving detection accuracy compared to conventional methods that detect only current. In addition, since it is reset using the output of the power detector, it is possible to incorporate the power detector, means for maintaining the shattered state, and means for returning from the shattered state on one circuit board. , an inexpensive electromagnetic contactor with fewer auxiliary contacts can be used, which not only makes the device less expensive, but also makes wiring work extremely simple, which has the effect of improving productivity.

[Brief explanation of the drawing]

1 and 2 are circuits of a conventional hoisting device, with FIG. 1 being an overall diagram and FIG. 2 being a detailed diagram of a control circuit. 3 and 4 are circuit diagrams of an embodiment of the present invention, where FIG. 3 is an overall diagram, FIG. 4 is a detailed diagram of the control circuit, and FIG. 5 is a characteristic diagram showing the detection characteristics of a conventional device. , FIG. 6 is a waveform diagram showing the voltage, current, and power waveforms of the present invention, and FIG. 7 is an enlarged diagram of the power waveforms. In the figure, M is a hoisting motor, CU is a magnetic contactor, CUa ₁ , CUa ₂ , CUa ₃ are normally open contacts, CUb is a normally closed contact, CD is a magnetic contactor, CDa ₁ , CDa ₂ , CDa ₃
is a normally open contact, CDb is a normally closed contact, TR ₁ and TR ₂ are power detectors, CT ₂ is a current detector, CC ₂ is a control circuit,
Sp ₂ is a power detector, H ₂ is a comparator, K ₂ is a holding circuit as a first means, Rs is a reset circuit as a second means, RY is a relay, RYb is a normally closed contact,
Bu is a push button switch for winding up, and Bd is a push button switch for lowering. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1 Three-phase induction motor for hoisting, hoisting of this motor,
A reversible electromagnetic contactor that operates in response to hoisting operation, connected to the power supply side of this electromagnetic contactor, an operation switch that controls hoisting and hoisting operation of the motor, connected to the power supply side of the electromagnetic contactor, a voltage detector that detects the power supply voltage; a current detector that detects a motor current flowing to the load side of the contactor; a power detector that detects electric power based on the output of the voltage detector and the output of the current detector; A comparator that compares whether the output of the power detector has reached an overload state value during hoisting operation of the electric motor, and a hoisting operation circuit of the electric motor is interrupted and maintained by the output of the comparator. a first means, which is disposed on the same board as the first means, and when the electric motor is in a lowering operation, the output of the power detector is at a value corresponding to the lowering state, thereby causing the above-mentioned interruption state; A hoisting device comprising a second means for returning the.