JPH0717346B2 - Variable speed hoist - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a variable speed hoist in which speed control is performed by an inverter.

[Conventional technology]

Conventionally, as this type of device, there has been one using an inverter as disclosed in Japanese Patent Laid-Open No. 59-183594. This is such that the output frequency of the inverter is gradually increased when the hoisting or unwinding operation is started and the frequency is gradually lowered when the operation is stopped. The following measures have been taken against the danger of falling suspended loads due to insufficient torque when the frequency is low.

In other words, the motor is braked except during the hoisting or lowering operation, and when the output frequency exceeds a certain value during operation, a brake release signal for automatically releasing the brake is output. Further, when the operation is stopped, the output of the brake release signal is stopped when the output frequency becomes a certain value or less.

[Problems to be Solved by the Invention]

However, this device has a problem that if a failure occurs while the inverter outputs the brake release signal, the torque is lost when the operation is stopped, and the suspended load drops. Since this is dangerous, a safety device that mechanically locks the motor at the time of operation stop is used, but adding this function makes the weight heavier and the economy becomes worse. .

The object of the present invention is to prevent the suspended load from dropping even if the inverter is out of order and the brake release command is still issued without using a safety device that mechanically locks the motor. is there.

[Means for Solving the Problems]

In order to solve such a problem, a first invention relating to a variable speed hoist is a brake means and a rotor that are released / actuated in response to disconnection of a first disconnecting means for disconnecting an input power source. Has a rotation detection means for detecting the rotation direction and the number of rotations, has an electric motor capable of forward and reverse rotation in the winding and winding directions, and an output terminal connected to this electric motor and an input terminal connected to a power source, An inverter that changes the output power so as to change the rotation direction and rotation speed of the electric motor, operation signal transmission means for instructing the lowering operation of the electric motor, and connection and disconnection based on the operation signal of this operation signal transmission means. Second disconnection means for disconnecting the unwinding output power of the inverter corresponding to the disconnection, and disconnection corresponding to the second disconnection means and a first connection for the disconnection. Disconnection means The third connection / disconnection means, the connection / disconnection detection means for detecting connection / disconnection of the second connection / disconnection means, and the signal from the connection / disconnection detection means and the detection signal from the rotation detection means are set in advance. A brake emergency closing means having a storage means for outputting a command signal according to a determination condition, and a fourth arrangement arranged to exclusively open the first connecting / disconnecting means by the command signal of the brake emergency closing means. And a disconnecting means.

A second aspect of the variable speed hoist is a signal output by detecting that the second connection / disconnection means has been opened by the connection / disconnection detection means and a detection signal for detecting rotation from the rotation detection means. The cumulative value of the number of rotations of the electric motor is started and stored based on the above, and the preset value and the preset value are compared and judged, and when the cumulative value exceeds the initial value, a command signal is sent from the storage means. It is characterized by being output.

Furthermore, a third aspect of the variable speed hoist is that the release / correspondence of the first connection / disconnection means for connecting / disconnecting the input power source is released.
An electric motor having a braking means to be actuated and a rotation detecting means for detecting the rotation direction and the number of rotations of the rotor, capable of rotating forward and backward in the winding and winding directions, and an output terminal and a power supply connected to this motor. An inverter that has a connected input terminal and that changes the output power so as to change the rotation direction and rotation speed of the electric motor, operation signal transmission means for instructing the winding operation of the electric motor, and operation signal of this operation signal transmission means. Fifth disconnecting means for disconnecting the winding output power of the inverter in response to the disconnection, and disconnecting corresponding to the fifth disconnecting means. Corresponding to the third disconnecting means for disconnecting the first disconnecting means, the disconnection detecting means for detecting disconnection of the fifth disconnecting means, and the signal from the disconnection detecting means and the rotation detecting means. Electric The brake emergency closing means having a storage means for outputting a command signal in accordance with a judgment condition preset based on a detection signal that the wheel is rotating in the unwinding direction, and a command of this brake emergency closing means And a fourth connecting / disconnecting means arranged so as to exclusively open the first connecting / disconnecting means by a signal.

[Action]

A first aspect of the variable speed hoist is preset based on a signal from a disconnection detecting means for detecting disconnection of the second disconnecting means during a lowering operation and a detection signal from a rotation detecting means. It is possible to open the first disconnection means exclusively by making a determination according to the determination condition and outputting a command signal from the storage means to the fourth disconnection means. Nevertheless, if the brake does not close, the brake power circuit can be forcibly opened to operate the brake.

Further, in the second aspect of the variable speed hoist, the determination of outputting the command signal to the fourth disconnecting means is performed by comparing and determining the cumulative value of the rotation speed of the electric motor and a preset initial value. Therefore, it is possible to easily and surely determine the abnormality and control the stop distance.

Further, a third aspect of the variable speed hoist is that a signal from a connection / disconnection detection means for detecting connection / disconnection of the fifth connection / disconnection means and an electric motor from the rotation detection means rotate in the unwinding direction during winding operation. It is determined based on the detection signal that there is a predetermined condition, and a command signal is output from the storage means to exclusively open the first connection / disconnection means. When the brake does not close even though there is no motor output for hoisting, the brake power supply circuit can be forcibly opened to operate the brake.

〔Example〕

 FIG. 1 is a circuit diagram showing an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an inverter unit as an inverter, which is supplied with a three-phase AC power source from power supply lines R, S, and T and outputs a three-phase AC power for which the voltage and frequency are variable, as described later. Reference numeral 2 denotes a hoisting motor, which rotates in a rotation direction and a speed corresponding to the order and frequency of phase rotation of the three-phase AC output from the inverter unit 1. Reference numeral 3 denotes a brake, which is in a locked state so that the hoisting motor 2 does not rotate when not energized, and is in an open state so that the hoisting motor 2 can freely rotate when energized. PBu is a push button switch as a means for transmitting operation signals for hoisting operation. It is an automatic reset type and a two-stage push type. This switch closes the normally open contact PBul when pushed to the first step, and normally open contact PBuh when pushed to the second step.
Is supposed to close. PBd is a push button switch for lowering operation as an operation signal transmitting means, which is an automatic reset type and a normally open two-stage push type. This switch closes the contact PBdl when pushed to the first step and closes the contact PBdh when pushed to the second step. The push button switches PBu and PBd are configured so that they cannot be pushed simultaneously by a mechanical interlock.

Reference numeral 4 is a coil of an electromagnetic relay which constitutes a fifth disconnecting means, and has a normally open contact 4a ₁ for instructing the inverter unit 1 to output three-phase alternating current in the order of phase rotation in which the winding motor 2 rotates in the winding direction. Open and close. Reference numeral 5 is a coil of an electromagnetic relay that constitutes a second connection / disconnection means, and the inverter unit 1 is arranged in the order of phase rotation in which the winding motor 2 rotates in the winding direction.
Opens and closes the normally-open contact 5a ₁ that instructs to output three-phase AC. Also, the normally open contact 5a ₂ is opened and closed. This normally open contact 5
a _{2 also} serves as a disconnection detecting means.

Reference numeral 6 denotes a coil of an electromagnetic relay which constitutes a third disconnecting means, which is excited while the inverter 1 outputs a three-phase alternating current and opens and closes the normally open contacts 6a ₁ and 6a ₂ . Reference numeral 7 is a coil of an electromagnetic relay which constitutes the first connecting / disconnecting means, and opens and closes the normally open contacts 7a ₁ and 7a ₂ which energize the brake 3.

Reference numerals 8 and 9 are a high-speed setting device and a low-speed setting device, respectively, which are configured by variable resistors. Reference numeral 10 is a coil of an electromagnetic relay, which is excited when the push-button switch PBu or PBd is pushed to the second step, and the low-speed setter 9 is opened and closed by opening and closing the normally open contacts 10a ₁ and 10a ₂ and the normally closed contacts 10b ₁ and 10b _2. Is switched to the high speed setting device 8. Reference numeral 11 denotes a brake emergency closing means, which is provided with a normally open contact 6a after the normally open contact 5a ₂ is opened.
If a ₂ does not open, the normally closed contact 11b, which is the fourth disconnecting means, is opened. RE is a rotary encoder as rotation detection means, and 11d is a counter as storage means.

Next, the operation will be described with reference to FIG. 2 and FIG.

When the push button switch PBu is pushed to the first step at time t ₁ , the normally open contact 4a ₁ is closed, and the frequency of the inverter unit 1 is changed to the frequency f ₂ set by the low speed setting device 9 according to the preset inclination. Increase gradually. Time point
When the frequency reaches f ₁ at t ₂ , the inverter unit 1
Supplies power to the winding motor 2 and at the same time excites the coil 7 of the electromagnetic relay, so that the normally open contact 6a ₁ is closed.
At this time, since the normally closed contact 11b ₁ is still closed, the coil 7 is excited and the normally open contacts 7a ₁ and 7a ₂ are closed, the brake 3 is energized, the brake 3 is released, and the hoisting motor 2 is hoisted in the hoisting direction. Starts to rotate and accelerates. Time point
When the frequency f ₂ is reached at t ₃ , the inverter unit 1
Stops the increase of the frequency, so that the hoisting motor 2 is driven at a constant speed to rotate at a low speed.

When the push button switch PBu is further pushed to the second stage at time t ₄ , the coil 10 of the electromagnetic relay is also excited, the low speed setting device 9 is disconnected, and the high speed setting device 8 is connected. Then, the inverter unit 1 starts increasing the frequency again up to the frequency f ₃ set by the high-speed setting device 8 at a preset inclination, and the hoisting motor 2 speeds up again. Since the at time t ₅ reaches the frequency f ₃ inverter unit 1 stops increasing frequency, hoisting motor 2 is operated at constant speed in a high speed.

At time t ₆ , pushbutton switch PBu is changed from the second stage to 1
When returning to the stage, the high speed setting device 8 is switched to the low speed setting device 9, so that the inverter unit 1 starts to reduce the frequency due to the preset inclination. Since reaches the frequency f ₂ is reduced in frequency stops when t _7, hoist motor 2 is low-speed operation at a constant speed. Release the push button switch PBu at time t _8, the coil 4 of the electromagnetic relay is no longer energized, normally open contacts 4a ₁ is opened. Then, the inverter unit 1 decreases the frequency with a preset inclination, and when the frequency f ₁ is reached at time t ₉ , the inverter unit 1 stops the output to the hoisting motor 2 and at the same time, the coil 6 of the electromagnetic relay is excited. Since it disappears, the normally open contact 6a ₁ is opened, and as a result, the coil 7 is no longer excited, the normally open contacts 7a ₁ and 7a ₂ are opened, the brake 3 is de-energized, and the hoisting motor 2 is locked and stopped. .

When the push button switch PBd is pressed, the coil 5 of the electromagnetic relay is excited and the hoisting motor 2 only rotates in the hoisting direction, and other operations are the same.

Here, the operation of the brake emergency closing means 11 will be described. When the push button switch PBd for the lowering operation is pushed, the normally open contact 5a ₁ is closed, and at the same time when the lowering command is given to the inverter unit 1, the normally open contact 5a ₂ is closed. Since the inverter unit 1 excites the coil 6 at the time when the winding motor 2 starts outputting so as to rotate in the winding direction, the normally open contact 6a ₁ is closed and the brake 3
At the same time as opening, the normally open contact 6a ₂ closes. Then, when the push button switch PBd is released, the normally open contact 5a ₁ opens, and the inverter unit 1 stops the output of the coil 6, so the normally open contact 6a ₁ opens and the brake 3 opens. Brakes the hoisting motor 2.

However, if the inverter unit 1 has stopped the output but the coil 6 is not deenergized due to a failure,
Since the normally open contacts 6a ₁ and 6a ₂ remain closed, the brake 3
Keeps open. As a result, since the hoisting motor 2 is not supplied with power, no torque is generated and the suspended load begins to drop. Here, the brake emergency closing means 11
, From the time when the normally-open contact 5a ₂ are opened, the coil 6 is open the normally open contact 6a ₂ not energized, detects the lowering rotation amount until the brake 3 starts to lock the motor 2 hoist. If the coil 6 continues to be excited due to a failure and the suspended load drops, the normally open contact 6a ₂
Detected by the rotary encoder RE that the lowering rotation amount until opening exceeds the counter 11d is counted up, opening the normally open contact 11b _1. Then, the coil 7 is not excited and the brake 3 locks the hoisting motor 2,
It is possible to prevent the hanging load from falling.

That is, the steps shown in the flow chart of FIG.
When it is determined at 20 that the normally open contact 5a ₂ is on, the counter 11d is reset at step 22, and the normally open contact 5a ₂ is reset.
Is off and the normally open contact 6a ₂ is off, it is reset in the same manner. When it is determined in step 21 that the normally open contact 6a ₂ is on, it is determined whether or not the counter 11d has counted up in step 23. If the counter is incremented here, the normally closed contact 11b ₁ is opened in step 24, and if not counted, the counting of the falling pulse is continued in step 25.

FIG. 4 is a diagram showing a second embodiment of the present invention.
In the figure, the same symbols are used for the same or corresponding portions as in FIG.

In FIG. 4, reference numeral 13 is a coil of an electromagnetic relay, which opens and closes the normally open contact 13a ₁ for self-holding and the normally open contact 13a ₂ in series with the normally open contact 4a ₁ so that the normally open contact 4a ₁ When it is on, it instructs the inverter unit 1 to output a three-phase alternating current in a phase order in which the winding motor 2 rotates in the winding direction.

Reference numeral 14 is a tachometer as a rotation detecting means for generating a DC voltage having a voltage and a polarity depending on the rotation speed and the rotation direction of the winding motor 2. Reference numeral 15 denotes a fall detector as a brake emergency closing means, which inputs a signal from the tachogenerator 14 and at the same time inputs a normally open contact 4a ₂ of a coil 4 of an electromagnetic relay which instructs a winding operation. Therefore, when a voltage having a polarity indicating that the hoisting motor 2 is rotating in the hoisting direction is input from the tacho generator 14 despite the hoisting operation being instructed, the suspended load drops. The normally closed contacts 15b ₁ and 15b ₂ serving as the fourth disconnecting means are opened. The type of normally open contacts 5a ₃ of the clutching detecting means, indicating that instructs driving down winding. When the push button switch as the operation signal transmitting means is stopped during the lowering, and the stop does not stop even when the push button switch is wound down beyond the normal deceleration stop distance, the drop detector 15 has the normally open contact 15
The b ₂ is opened, the brake 3 is de-energized, and the rotation of the hoisting motor 2 is restricted (locked) and stopped.

The operation of this device is as follows. When the three-phase power is supplied from the power supply lines R, S, T, the electromagnetic relay coil 13
Does not hold itself. When the push button switch PBd is pushed to the first step at the time point t ₁ shown in FIG. 5, the normally open contact 5a ₁ is closed. At this time, since the normally open contact 15b ₁ of the drop detector is also closed, the coil 13 of the electromagnetic relay is excited and the normally open contact 13a ₁ is closed. Therefore, the coil 13 is in a self-holding state, and the normally open contact 13a ₂ also remains closed. At the same time, the normally open contact 5a ₁ closes and the inverter unit 1 begins to increase the output frequency with a preset slope (the normally open contact 13a ₂ does not contribute to the frequency increase in this case).

When the frequency reaches f ₁ at time t ₂ , the inverter unit 1 starts supplying power to the hoisting motor 2 and excites the coil 6 of the electromagnetic relay.
₁ is closed, the coil 7 of the electromagnetic relay is excited, and the normally open contact 7
The a ₁ and 7 a ₂ are closed, the brake 3 is energized, and the hoisting motor 2 is unlocked. Then, the hoisting motor 2 starts to rotate in the hoisting direction and accelerates.
Upon reaching the time point t _3, the inverter unit 1 will stop the increase in frequency, hoisting motor 2 is slower wound down operation at constant rotation frequency f _2.

When the push button switch PBd is pushed further to the second stage at time t ₄ , the coil 10 of the electromagnetic relay is excited, the low speed setting device 9 is disconnected, and the high speed setting device 8 is connected. Then, the inverter unit 1 starts increasing the frequency again up to the frequency f ₃ set by the high-speed setting device 8 with a preset inclination, so that the hoisting motor 2 speeds up again. Upon reaching the frequency f ₃ at time t _5, the inverter unit 1 will stop the increase in frequency, hoisting motor 2 is accelerated wound down operated at constant speed.

At time t _6, and back to the first stage the push button switch PBd from the second stage, since the switches from the high speed setter 8 in a low speed setter 9, inverter unit 1 begin to reduce the frequency slope that is set in advance. When at time t ₇ reaches the frequency f _2, since decrease of the frequency is stopped, hoisting motor 2 is operated at constant speed in a low speed.

When the push button PBd is stopped at time t ₈ , the coil 5 of the electromagnetic relay is no longer excited and the normally open contact 5a ₁
Opens. Then, the inverter unit 1 lowers the frequency again. When the time point t ₉ is reached, the inverter unit 1 stops the output to the hoisting motor 2 and at the same time, the electromagnetic relay coil 6 is no longer energized, so the normally open contact 6a ₁ is opened and the coil 7 is energized during normal operation. The normally open contacts 7a ₁ and 7a ₂ open, the brake 3 is de-energized, and the hoisting motor 2 is locked and stopped.

In the hoisting operation, when the push button switch PBu is pushed to the first step, the normally open contacts 4a ₁ and 4a _{2 of} the electromagnetic relay 4 are closed and the hoisting motor 2 first starts the hoisting operation at a low speed. At this time, if a load exceeding the rating is suspended, the torque of the hoisting motor 2 becomes insufficient, so that the hoisting motor 2 cannot be hoisted, the hoisting motor rotates in the unwinding direction, and the hoisted load begins to drop. Then, the tachogenerator 14 as the speed detecting means outputs a voltage having the polarity shown in the unwinding direction, and the drop detector 15 detects the drop of the suspended load. As a result,
Since the normally open contact 15b ₁ is opened, the self-holding of the electromagnetic relay coil 13 is released, and the normally open contact 13a ₂ is opened, so that the inverter unit 1 cannot output the three-phase AC to the hoisting motor 2 and the hoisting The motor 2 stops the winding operation.

At the time of winding down, if the user releases the push button switch at position 41 shown in FIG. 5 to stop the winding down instruction, the output frequency of the inverter unit 1 will decrease and the rotation speed of the winding motor 2 will decrease in both low speed and high speed operation. The speed of suspended loads is also reduced. In this case, when the inverter unit 1 is normal, it stops at the normal stop position 43 in both high speed and low speed.

On the other hand, when the inverter unit 1 fails and the electromagnetic relay coil 6 keeps issuing the brake release command, the hanging load is prevented from falling by the following method. When the push button switch is released, the inverter unit 1 gradually lowers the output frequency, so that the speed of the suspended load decreases and the speed decreases. Therefore, to some extent during deceleration, for example, the speed determined by the frequency f ₂ is set to the descent amount integration start speed 48
As specified. Then, the fall detector 15 supplied with the output of the tacho generator 14 integrates the output voltage of the tacho generator 14 from the time when the descending speed becomes equal to or lower than the descending amount integration start speed and starts integrating the descending amount. When the accumulated descent amount reaches a predetermined abnormality detection descent amount 49, the contact 15b ₂ is opened at the abnormality detection position 50 to eliminate the excitation of the coil 7, and the contacts 7a ₁ and 7a ₂ are opened to brake. Force the operation to restrain the rotation of the hoisting motor. Then, the suspended load will stop at the forced stop position 51 in the event of an abnormality.

In this case, in the embodiment shown in FIG. 1, as shown in FIG. 5, the abnormality detection drop amount 49 when stopping from the lowering operation state at a high speed and the abnormality detection when stopping from the low speed operation state If the descent amount 49a is set to the same value, in the case of lowering at a low speed, the abnormality detection descent amount 49a will be accumulated from the position 41a where the push button switch is released,
The abnormality detection position 50a is a position considerably lower than the abnormality detection position 50 of the present invention, and the speed of the suspended load is further added to accelerate the acceleration. Therefore, even if the brake is closed at the abnormality detection position 50a, the stop position becomes 51a, and the fall distance becomes large.

That is, since the frequency gradually decreases after the time t _{6 in} FIG. 2, the speed of the suspended load gradually decreases. However, at the time point t ₉ that speed becomes a minimum, at the normal time there would be no torque of the motor 2 hoist because power to the motor 2 hoisting and passes that point is not supplied. On the other hand, the brake release command remains issued due to the failure of the inverter unit 1. Therefore, from the time point t ₉ onward, neither the braking force by the torque nor the braking force by the brake works, so that the suspended load will drop as it is.

Therefore, in the embodiment of the present invention, it is detected that the lowering speed of the suspended load has decreased to a speed corresponding to the frequency of the frequency f ₂ near integrates the decrease amount from that point, it lowering amount of normal when it is a value exceeding, to deenergize the coil 7 by opening the contacts 15 _b2, since opening the contacts 7 _a1, 7 _a2, winding motor 2 is locked.

FIG. 6 is a flowchart showing this state. First, the operation at the time of abnormality will be described. When it is detected in step 100 that the push button switch has been released, and it is determined that the descent rate of the suspended load is slower than the descent amount integration start speed in step 101, the integration start memory set processing is performed as shown in step 102. Done. Then, in step 104, the integration start memory set is determined, and the amount of decrease is counted. If it is determined in step 105 that the count exceeds the abnormality detection amount, the brake braking process is performed as shown in step 106.

If it is detected in step 101 that the speed is lower than the descent amount start speed during normal operation, the processing of the accumulation start memory set in step 102 is performed, it is detected in step 104, and the abnormality detection amount is exceeded in step 105. It is determined whether or not. However, in a normal state, it is determined in step 107 that the brake release command from the inverter has stopped before exceeding this value, so as shown in step 108, the process of the integration start memory set is followed by step 10
The brake braking process of 9 is performed.

If the pushbutton switch is not released, step
At 103, the integration start memory is reset. At this time, it is determined that the brake release command shown in step 107 is not stopped, so the brake release process shown in step 110 is being performed.

That is, when normal, brake braking is performed in step 109, and when failure occurs, brake braking is performed in step 106.

The push button switch is a two-step push type,
The one-step pushing type may be used as the one-step speed, and the tacho generator is used to detect the rotation speed of the hoisting motor, but a rotary encoder may be used.

〔The invention's effect〕

As described above, in the first aspect of the variable speed hoist, the signal from the disconnection detecting means and the detection signal from the rotation detecting means for detecting the disconnection of the second disconnecting means during the unwinding operation is provided. It is possible to exclusively open the first connecting / disconnecting means by making a determination according to a determination condition set in advance based on a determination condition and outputting a command signal from the storage means to the fourth connecting / disconnecting means. If the brake does not close even though there is no output, you can forcibly open the brake power circuit and operate the brake.
Even if the brake power supply circuit is not opened due to the failure of the inverter when the operation switch, which is the normally open contact, is opened during the unwinding operation, there is an effect that the accident of dropping the cargo can be prevented.

Further, in the second aspect of the variable speed hoist, the determination of outputting the command signal to the fourth disconnecting means is performed by comparing and determining the cumulative value of the rotation speed of the electric motor and a preset initial value. Since the abnormality can be determined and the stop distance can be controlled easily and surely, the variable speed hoist equipped with the highly reliable fall prevention device can be configured.

Further, a third aspect of the variable speed hoist is that a signal from a connection / disconnection detection means for detecting connection / disconnection of the fifth connection / disconnection means and an electric motor from the rotation detection means rotate in the unwinding direction during winding operation. Based on the detection signal indicating that the first disconnection means is present, a determination is made according to a preset determination condition, and a command signal is output from the storage means to the fourth connection / disconnection means to exclusively perform the first operation.
Since the connecting / disconnecting means can be opened, if the brake does not close even if there is no motor output for winding, the brake power circuit can be forcibly opened and the brake can be operated. Even if a situation occurs in which the brake power supply circuit is not opened due to a failure of the inverter when the operation switch, which is a normally open contact, is opened, it is possible to prevent the accident of dropping the load.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing changes in the output frequency of an inverter, FIG. 3 is a flow chart for explaining the main operation of FIG. 1, and FIG. To FIG. 6 are diagrams showing another embodiment, FIG. 4 is a circuit diagram, FIG. 5 is a diagram for explaining a stop position, and FIG. 6 is a flow chart for explaining the operation of FIG. . 1 ... Inverter unit as an inverter, 2 ...
Winding motor, 3 ... Brake, 4,5,6,7,10,13 ... Electromagnetic relay coil, 11 ... Brake emergency closing means, 14 ...
… Tacho generator, 15… Fall detector.

Claims (3)

[Claims] 1. A brake means that is released / operated in response to a connection / disconnection of a first connection / disconnection means for connecting / disconnecting an input power source, and a rotation detection means for detecting a rotation direction and a rotation speed of a rotor, It has an electric motor that can be rotated forward and backward in the hoisting and unwinding directions, an output terminal connected to this electric motor, and an input terminal connected to a power supply.The output electric power is changed so as to change the rotating direction and the rotating speed of the electric motor. The inverter to be changed, the operation signal transmitting means for instructing the lowering operation of the electric motor, and the disconnection output power of the inverter corresponding to the connection and disconnection based on the operation signal of the operation signal transmitting means. A second disconnecting means for disconnecting the first disconnecting means and a third disconnecting means for disconnecting the first disconnecting means corresponding to the second disconnecting means. , The second disconnector A disconnection detecting means for detecting the disconnection of the device, and a storage means for outputting a command signal according to a preset determination condition based on the signal from the disconnection detecting means and the detection signal from the rotation detecting means. A variable speed hoist comprising: a brake emergency closing means provided therein; and a fourth disconnecting means arranged so as to exclusively open the first disconnecting means in response to a command signal from the brake emergency closing means. 2. The electric motor of the motor is detected based on a signal output by the connection detecting means detecting that the second connecting means is opened and a rotation detection signal from the rotation detecting means. The accumulation of the cumulative value of the number of revolutions is started and stored, and a preset initial value and the above cumulative value are compared and judged, and when the cumulative value exceeds the initial value, a command signal is output from the storage means. The variable speed hoist according to claim 1, wherein: 3. A brake means that is released / operated in response to the connection / disconnection of a first connection / disconnection means for connecting / disconnecting an input power source, and rotation detection means for detecting the rotation direction and the rotation speed of the rotor, It has an electric motor that can be rotated forward and backward in the hoisting and unwinding directions, an output terminal connected to this electric motor, and an input terminal connected to a power supply.The output electric power is changed so as to change the rotating direction and the rotating speed of the electric motor. The inverter to be changed, the operation signal transmitting means for instructing the winding operation of the electric motor, and the disconnection based on the operation signal of the operation signal transmitting means, and the winding output power of the inverter is connected in response to the disconnection. A fifth disconnecting means for disconnecting; a third disconnecting means for disconnecting corresponding to the fifth disconnecting means and for disconnecting the first disconnecting means corresponding to the disconnection; Fifth stop Was previously set based on a disconnection detecting means for detecting disconnection of the motor, and a signal from the disconnection detecting means and a detection signal from the rotation detecting means that the electric motor is rotating in the unwinding direction. A brake emergency closing means having a storage means for outputting a command signal in accordance with a determination condition, and a first emergency disconnecting means arranged to exclusively open the first disconnecting means by a command signal from the brake emergency closing means. Variable speed hoist with 4 disconnecting means.