JPH0114633Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] This invention relates to a control device for variable speed control of a drive motor of an electric hoist.

[Conventional technology and problems]

Generally, a squirrel cage induction motor is used as a drive motor for an electric hoist, and the capacity of the motor is selected according to the rated load and rated speed of the hoist. The drive control system is generally configured to drive the squirrel cage induction motor at its rated speed, regardless of the weight of the load. Constant speed operation that ignores the light weight of the load naturally results in poor work efficiency.

In order to overcome this drawback, it is conventionally known to use a squirrel-cage induction motor of the pole number converting type, and to raise and lower the motor at a speed approximately twice the rated speed when the load is light. However, in this case, if the motor and hoist are specially designed, it will be sluggish, resulting in a large and heavy device. Therefore, the above configuration cannot be easily applied to a standard general-purpose hoist, resulting in an expensive special device.

[Purpose of invention]

The purpose of this invention is to create an electric hoist with a configuration that can be easily applied in addition to a standard general-purpose hoist, and which can increase work efficiency by automatically increasing the operating speed when the load is light. The purpose of this invention is to provide a control device.

[Summary of the idea]

In order to achieve the above objective, this invention is equipped with a load cell to detect the lightness of the hoist load and an inverter that serves as a power source for the hoist drive motor. An automatic switching control circuit is installed so that the motor is driven at approximately the rated speed when the output of the load cell is lower than a predetermined value, and the motor is driven at a speed that is sufficiently higher than the rated speed using the output of the inverter when the load cell output is less than a predetermined value. It is characterized by having been established.

[Explanation of Examples]

Examples of this invention are shown below in Figures 1 to 2.
This will be explained with reference to the figures.

1 and 2 show a control device for an electric hoist according to an embodiment of the invention, FIG. 1 is an electrical wiring diagram of the main circuit section, and FIG. 2 is an electrical wiring diagram of the control circuit section. In FIG. 1, 10 is a three-phase AC power source that is the power source for the electric hoist and the control device;
is a squirrel cage induction motor that drives the electric hoist to move up and down; 2 is an electromagnetic brake that stops the hoist from moving up and down; 5 is an inverter that is a variable frequency power supply;
LS is a limit switch. The inverter 5 is
The input from the AC power source 10 is once forward converted and then reverse converted to output three-phase AC having a frequency about two to three times that of the AC power source 10. When the motor 1 is directly driven by the output of the AC power supply 10, it rotates at approximately the rated speed, and when it is driven by the output of the inverter 5, it rotates at a predetermined speed that is two to three times the rated speed (set to avoid overloading). rotate).

In FIG. 2, 3a and 3b are upward operation switches that are linked to each other, and 4a and 4b are downward operation switches. Reference numeral 6 is a load meter contact point for detecting the lightness or weight of the hoist load, which is turned on when the load is lighter than the setting. Also, LL is a load detection relay, LL ₁ to _{LL 4} are its contacts, MU is a lift command relay for hoist lifting operation,
MU ₁ to MU ₄ are its contacts, MD is a lowering command relay for lowering the hoist, and MD ₁ to _{MD 4} are its contacts. MUX is a relay for positive phase rotation command to switch the phase rotation of the AC output of the inverter 5,
MUX ₁ to MUX ₃ are its contacts, MDX is a reverse phase rotation command relay for switching the phase rotation of the AC output of the inverter 5, and MDX ₁ to MDX ₃ are its contacts. MI is an operation switching relay for switching the AC power supply 10, which is the first power supply, and the inverter 5, which is the second power supply, as the power supply for the squirrel cage induction motor 1, MI ₁ and MI ₂ are the contacts, and MB is the brake 2. Brake control relay to control, MB ₁ is its contact point.

As shown in Fig. 1, the squirrel-cage induction motor 1 has a normally open contact (hereinafter abbreviated as contact) MU ₄ of the relay MU for ascending commands and a contact of the relay MD for descending commands.
It is connected to an AC power supply 10 via a parallel circuit consisting of an MD ₄ and a limit switch LS, and constitutes a first drive circuit 12 of the hoist. The electromagnetic brake 2 is connected to an AC power source 10 through a series circuit consisting of a limit switch LS, a rectifier 7, and an a contact _MB1 of a brake control relay MB, thereby forming a brake circuit 11. Inverter 5 is the a contact MI ₂ of the operation switching relay MI
It is connected between the power supply 10 and the squirrel cage induction motor 1 via the limit switch LS and constitutes a second drive circuit 13. Therefore, the first of these
The drive circuit 12, the brake circuit 11, and the second drive circuit 12 constitute a main circuit section.

As shown in FIG. 2, the load detection relay LL is connected in series to the contact 6 of the load cell, and a load detection circuit 14 is constituted by these. The rising command relay MU for the first drive circuit includes the rising operation switch 3a, the lowering command operation switch 4b, the normally closed contact (hereinafter referred to as the b contact) of the load detection relay LL _LL1 , and the first drive circuit. It is connected in series to a series circuit consisting of the b contact MD ₁ of the lowering command relay MD for the first drive circuit, thereby configuring a rising command circuit 15 for the first drive circuit. The descending command relay MD is the b contact of the ascending operation switch 3b, the descending operation switch 4a, and the load detection relay LL.
It is connected in series to a series circuit consisting of LL ₂ and the b contact MU ₁ of the rise command relay MD, and constitutes a first rise command circuit 16 for the first drive circuit.

In addition, the relay MUX for normal phase rotation command for the second drive circuit includes switches 3a and 4b, limit switch LS, a contact LL ₃ of load detection relay LL, and relay for negative phase rotation command for the second drive circuit.
It is connected in series to a series circuit consisting of the b contact MDX ₂ of the MDX, and constitutes a positive phase rotation command circuit 17 for the second drive circuit. Relay for reverse phase rotation command
MDX is switch 3b, 4b, load detection relay
LL a contact LL ₄ and relay for positive phase rotation command
It is connected in series to a series circuit consisting of the b-contact MUX ₂ of the MUX, and constitutes an anti-phase rotation command circuit 18.

The operation switching command relay MI consists of a series circuit of the a contact MUX ₃ of the relay MU and the a contact MDX ₃ of the relay MDX, the b contact MU ₂ of the relay MU, and the relay MD.
The operation switching circuit 19 is connected in series to a series circuit consisting of the b-contact MD ₂ . Brake control relay MB is the a contact of relay MU
MU ₃ , relay MD a contact MD ₃ and relay MI
A brake control circuit 20 is configured by connecting in series to a parallel circuit consisting of a contact _MI1 .

In the control device configured as described above, the phase rotation direction of the output of the inverter 5 is controlled by relay contacts MUX ₁ and MDX ₁ . When motor ₁ is driven by the output of inverter 5 while contact MUX 1 is on, motor 1 rotates forward (the hoist rises) and the contact
When MDX ₁ is on, motor 1 rotates in reverse (the hoist descends).

The LS is a limit switch and turns off when the hoist reaches its upper limit.

During normal load (heavy load) when load cell contact 6 is off, relay LL is not driven and b
Contacts LL ₁ and LL ₂ are on, and A contacts LL ₃ and LL ₄ are off. So, for example, the lift operation switch 3
Press a and 3b, turn 3b off and 3a on. Then relay MU is energized and b contact MU ₁
and MU ₂ turns off, and a contacts MU ₃ and MU ₄ turn on. When contact MU ₃ is turned on, relay MB is driven, and its contact MB ₁ is turned on. Contact MB ₁
When turned on, the electromagnetic brake 2 is driven and the brake is released. At the same time, the contact MU ₄ is turned on, so that the motor 1 is directly driven by the AC power supply 10 via the contact MU ₄ , and the motor 1 rotates at approximately the rated speed to raise the hoist at the rated speed.

Release your hands from the lift operation switches 3a and 3b,
If 3b is turned on and 3a is turned off, relay MU and
MB is no longer driven, motor 1 is stopped, and electromagnetic brake 2 is activated.

The case where the lowering operation switches 4a and 4b are pressed is almost the same as the above. In this case, relay MD
MB is driven, motor 1 is directly driven by AC power supply 10 through contact MD ₄ , and the hoist is lowered at the rated speed.

Next, when the hoist is under a light load (including no load), load cell contact 6 is turned on and relay LL is driven, and its a contacts LL ₃ and LL ₄ are turned on.
B contacts LL ₁ and LL ₂ are turned off. In this state, for example, if you press the lift operation switches 3a and 3b, the relay MDX will be driven, and its a contacts MUX ₁ and MUX _{3 will} be activated.
is on, and b contact MUX ₂ is off. contact
When MUX ₃ is turned on, relay MI is driven and its contacts MI ₁ and MI ₂ are turned on. When contact MI ₁ is turned on, relay MB is activated and its contact MB ₁
is turned on, the electromagnetic brake 2 is energized, and the brake is released.

On the other hand, since contact MUX ₁ is turned on,
The inverter 5 outputs phase sequential outputs for normal rotation of the motor 1. Its output is applied to motor 1 through contact MI ₂ which is turned on at the same time. The motor 1 now rotates at a high speed 2 to 3 times the rated speed and raises the hoist at high speed.

When the lift operation switches 3a, 3b are released, the relays MUX, MI, MB are no longer driven, the contacts _MUX1 , _MI2 , _MB1 are turned off, the motor 1 is turned off, and the brake is applied.

When the lowering operation switches 4a and 4b are pressed, the operation is similar to that described above. In this case, the relay
MDX, MI, MB are driven, contacts MDX ₁ , MI ₂ ,
MB ₁ is turned on. In other words, the inverter 5 generates an output with a phase sequence opposite to that described above, which causes the motor 1 to rotate in reverse at high speed.

Note that a braking resistor Rb is provided in the inverter 5 in order to absorb the regenerated power generated from the motor 1 during the downward movement of a light load.

[Effect of idea]

As explained in detail above, the electric hoist control device according to this invention has a simple configuration of adding an inverter, a load meter, and some circuits to a normal general-purpose hoist, and can be operated at high speed under light loads. It is possible to realize a hoist with high work efficiency.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the main circuit section of a control device according to an embodiment of the invention, and FIG. 2 is a circuit diagram of the control circuit section. 1... Hoist drive motor, 2... Electromagnetic brake, 3a, 3b... Lifting operation switch, 4a,
4b...Descent operation switch, 5...Inverter, 6...Load cell contact, 12...First drive circuit, 13...Second drive circuit, 14...Load detection circuit, 15...Rise command Circuit, 16...Descent command circuit, 17...Normal phase rotation command circuit, 18...Negative phase rotation command circuit, 19...Operation switching circuit, LL...
Load detection relay, MU...Relay for ascending command,
MD...Relay for descending command, MUX...Relay for normal phase rotation command, MDX...Relay for reverse phase rotation command, MI...Relay for operation switching command.

Claims (1)

[Claims for Utility Model Registration] A main circuit section having a drive motor for driving a hoist, a brake means for regulating the rotation of the drive motor, and a drive motor for driving the hoist by operating a lifting operation switch and a lowering operation switch for the hoist. An electric hoist control device comprising a control circuit unit that rotates a motor forward or backward to move the hoist up and down, wherein the main circuit unit includes a first circuit that rotates the drive motor forward and backward at a predetermined speed using an AC power source. Drive circuit 1
2, and a second drive circuit 13 having an inverter 5 that rotates the drive motor 1 in forward and reverse directions at a speed greater than the predetermined speed; A contact 6 of the load cell that turns off when the value is large and turns on when the value is smaller than the predetermined value, and a load detection relay LL that operates or deactivates depending on the off or on operation of this contact 6.
a load detection circuit 14 consisting of a load detection circuit 14; and a lift command relay that operates when the load detection circuit 14 is not activated by operating the lift operation switch, operates the first drive circuit 12, and rotates the drive motor 1 in the forward direction. When the load detection circuit 14 is not operating, the first drive circuit 12 is activated by operating the ascent command circuit 15 having an MU and the descent operation switch.
a lowering command circuit 16 having a lowering command relay MD that operates the drive motor 1 to rotate the drive motor 1 in the reverse direction; a positive phase rotation command circuit 17 having a positive phase rotation command relay MUX that rotates the output of the inverter 5 in a positive phase; Relay for reverse phase rotation command that rotates the output in reverse phase
A reverse phase rotation command circuit 18 having an MDX, which operates when the normal phase rotation command relay MUX or the reverse phase rotation command relay MDX is in operation and when the up command relay MU and the down command relay MD are not in operation. An electric hoist control device comprising an operation switching circuit 19 for switching from hoist operation by the first drive circuit 12 to hoist operation by the second drive circuit 13.