JP2588665B2 - Motor overload detection device for hoist - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor overload detecting device for a hoist having an induction motor as a hoist motor.

[0002]

2. Description of the Related Art FIG. 11 shows, for example, JP-A-51-33451.
FIG. 1 is a circuit diagram of a conventional motor overload detection device for a hoist disclosed in Japanese Patent Application Laid-Open Publication No. HEI 10-205139. 1 is a three-phase induction motor, a three-phase power line R,
A three-phase alternating current is supplied from S and T. 2 is a power detector for detecting the power supplied to the three-phase induction motor 1, 3 is
This is a converter for converting the output of the power detector 2 into a voltage or another electric quantity.

[0003] A comparator 4 determines whether the output of the converter 3 exceeds a reference value for overload detection, and generates an output when the output exceeds a predetermined reference value. Reference numeral 5 denotes a determination circuit for determining whether or not the three-phase induction motor 1 is in an activated state, and includes a delay relay and the like. Reference numeral 6 denotes an overload detection circuit, which includes an AND circuit, and generates an output only when both the output of the comparator 4 and the output of the determination circuit 5 are generated.

The three-phase power lines R, S, T are turned on / off by a power switch (not shown). A pulley for lifting a load is also connected to the rotating shaft of the three-phase induction motor 1 via a speed reducer (not shown).

Next, the operation of the motor overload detecting device shown in FIG. 11 will be described. FIG. 12 is an operation characteristic diagram showing a relationship between voltage and power of the motor overload detection device in FIG.

When a normal load equal to or less than the rated load is lifted in the above configuration, a large amount of electric power is required to accelerate the hoisting motor at startup, even if the load is light. For this reason, the power detector 2 detects a large power of a certain value or more. Thus there is a momentary from comparator 4 is output is input to the overload detection circuit 6 generates. However, at this time, no output is output from the discriminating circuit 5 because it is a start-up time. Thus AND circuit of the overload detection circuit 6 does not generate an output.

[0007] After the start, the electric power settles to a steady small electric power value at the time of normal load indicated by a solid line in FIG. Therefore, no output is generated from the comparator 4. Thereafter, judgment circuit 5 generates the start and end time output, since there is no output of the comparator 4 output from the over <br/> load detection circuit 6 is not generated, the three-phase induction motor 1 is operated in a steady do.

On the other hand, when a heavy load exceeding the rated load is hung, large electric power during overload is detected by the power detector 2 even after the start-up, as shown by the broken line in FIG. Thus, comparator 4 produces an output. At the same time, an output is also generated from the determination circuit 5 after startup. Therefore
An output is generated from the AND circuit of the overload detection circuit 6.

[0009] The overload and generate an alarm in response to the output of the detecting circuit 6 or a three-phase induction motor or disconnected from the power supply, to eliminate the overload condition.

[0010]

The conventional motor overload detecting device for a hoist has the following problems because it is constructed as described above. Complex and expensive devices such as a power detector that detects current, voltage, and power factor to calculate power, and a decision circuit that responds to the input of a hoisting command and determines whether or not it is at startup with a delay relay or the like is required.

The first invention of the present invention has been made to solve the above-mentioned problems, and can be started without using an expensive power detector or a complicated winding command input / delay relay circuit. It is an object of the present invention to obtain a motor overload detection device for a hoist capable of determining whether or not it is time and detecting an overload state even during a lowering operation.

The second invention of the present invention has also been made in order to solve the above-mentioned problems, and can be started without using an expensive power detector or a complicated winding command input / delay relay circuit. It is an object of the present invention to obtain a safe and easy-to-use motor overload detection device for a hoist that determines whether or not it is time, and when an overload is detected during a hoisting operation, retains its output until it starts a lowering operation. I do.

[0013]

According to a first aspect of the present invention, there is provided a motor overload detecting apparatus for a hoist, wherein a rotation detector for detecting a rotational speed of an induction motor of the hoist, and a temperature of the induction motor. , A voltage detector for detecting a voltage applied to the induction motor, and an induction motor responsive to the temperature detection value detected by the temperature detector and the voltage detection value detected by the voltage detector. Reference speed determination means for determining a reference rotation speed, and determination means for determining overload of the induction motor based on the rotation speed detected by the rotation detector and the reference rotation speed determined by the reference speed determination means. , Is provided.

According to a second aspect of the present invention, there is provided a motor overload detecting apparatus for a hoist, comprising: a rotation detector for detecting a rotation speed of an induction motor of the hoist; and a temperature detector for detecting a temperature of the induction motor. A voltage detector that detects an applied voltage to the induction motor, and a reference rotation speed of the induction motor based on the temperature detection value detected by the temperature detector and the voltage detection value detected by the voltage detector. A reference speed determining means for determining, and an overload for determining an overload of the induction motor when the rotation speed detected by the rotation detector during the hoisting operation is lower than the reference rotation speed determined by the reference speed determining means. Determining means, holding the output of the overload determining means,
Output holding means for canceling the holding of the output of the overload determining means in response to the stop of the hoisting operation or the start of the lowering operation.

[0015]

A motor overload detecting device for a hoist according to a first aspect of the present invention determines a reference speed value of an induction motor based on detection values of a voltage detector and a temperature detector, and detects the reference speed value by a rotation detector. The overload state of the induction motor is determined by comparing the reference rotation speed with the set rotation speed.

A motor overload detecting device for a hoist according to a second aspect of the present invention determines a reference speed value of an induction motor based on detection values of a voltage detector and a temperature detector. When the rotation speed detected by the rotation detector falls below this reference speed, the overload determination means
An overload state of the induction motor is determined, and an output indicating the overload state is held until the hoisting operation is stopped or the lowering operation is started.

[0017]

FIG. 1 is a circuit diagram of a motor overload detecting apparatus according to a first embodiment of the present invention. Reference numeral 1 denotes a three-phase induction motor to which three-phase alternating current is supplied from three-phase power lines R, S, and T. Reference numeral 7 denotes a rotation detector including a tacho generator, which outputs a voltage signal having a polarity and a magnitude corresponding to the rotation direction and rotation speed of the three-phase induction motor 1. Reference numeral 8 denotes a voltage detector which detects and outputs a voltage between the R and S lines of the three-phase power lines R, S and T. 9
Is a temperature detector that outputs a voltage signal corresponding to the temperature of the three-phase induction motor 1. Reference numeral 10 denotes an overload detection circuit, and a voltage detector 8
And the reference rotation speed value is determined in accordance with the output of the temperature detector 9, and it is determined that the startup has been completed based on the output of the rotation detector 7. Then, the comparison result between the output of the rotation detector 7 and the reference speed value is obtained. An overload is determined accordingly and an output is generated.

Next, the hoisting operation of the motor overload detecting device for the hoist according to the first embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 2 is a rotation speed characteristic diagram of the motor overload detection device of FIG. 1 during a hoisting operation. FIG. 3 is a characteristic diagram showing the relationship between the reference speed S0, the voltage, and the temperature during the hoisting operation of the motor overload detection device in FIG.

When hoisting a normal load less than the rated load,
When started at time t1, the three-phase induction motor 1 is instantaneously accelerated by a large starting torque, so that the speed temporarily reaches a speed S3 exceeding the synchronous speed S2. However, after around time t2, the speed S1 less than the synchronous speed S2. Calm down.

The overload detecting circuit 10 detects the start of winding in response to the start of the voltage signal of the polarity indicating the winding rotation from the rotation detector 7 at time t1. Further, the overload detection circuit 10 outputs the voltage detected by the voltage detector 8,
The hoisting reference speed S0 corresponding to the temperature detected by the temperature detector 9 is determined. The reference speed S0 depends on the temperature and the voltage, and the speed S0 corresponding to the temperature T2 and the voltage V1 is shown in FIG. In addition, temperature T1, temperature T2, temperature T3
Indicates the cases of high temperature, medium temperature and low temperature, respectively.

Further, at time t2, the overload detection circuit 10 determines that the start of the three-phase induction motor 1 has been completed in response to the output of the rotation detector 7, and then determines the rotation speed detected by the rotation detector 7. Since S1 exceeds the speed S0, it is determined that the load is a normal load below the rating, and no output is generated.

On the other hand, when a heavy load exceeding the rated load is hung, the speed settles to a speed S4 lower than the reference speed S0. Accordingly, the overload detection circuit 10 determines that the overload exceeds the rated load after determining that the winding start of the three-phase induction motor 1 has been completed at time t2, and generates an output.

Next, the lowering operation of the motor overload detecting device for the hoist according to the first embodiment of the present invention will be described with reference to FIGS. 1, 4 and 5. FIG. FIG. 4 is a rotation speed characteristic diagram during the lowering operation of the motor overload detection device of FIG. FIG. 5 is a characteristic diagram showing the relationship between the reference speed S0, the voltage, and the temperature during the lowering operation of the motor overload detection device of FIG.

Even when a normal load equal to or lower than the rated load is to be lowered, the three-phase induction motor 1 is instantaneously accelerated by a large starting torque when started at time t1. For this reason, although the overshoot greatly exceeds the normal speed S5, it is settled to the normal speed S5 equal to or higher than the synchronous speed S2 after about the time t2.

The overload detecting circuit 10 responds to the start of the lowering start in response to the start of the generation of the voltage signal having the polarity indicating the lowering rotation from the rotation detector 7 at the time t1. The overload detection circuit 10 detects the voltage V detected by the voltage detector 8.
Based on 1 and the temperature T2 detected by the temperature detector 9, the reference rotation speed S0D at the time of lowering is determined. After determining at the time t2 that the startup has been completed, the detected rotation speed S5
Is less than the reference speed S0D, it is determined that the load is normal or less than the rated load, and no output is generated.

However, when a heavy load exceeding the rated load is carried, the speed settles to a speed S6 exceeding the reference speed S0D. Accordingly, the overload detecting circuit 10 determines that the lowering start is completed at time t2, and then determines that the overload state exceeds the rated load, and generates an output.

FIG. 6 is a circuit diagram of a motor overload detecting apparatus according to a first embodiment of the second invention of the present invention. Reference numeral 1 denotes a three-phase induction motor to which three-phase alternating current is supplied from three-phase power lines R, S, and T. Reference numeral 7 denotes a rotation detector including a tacho generator, which outputs a voltage signal having a polarity and a magnitude corresponding to the rotation direction and rotation speed of the three-phase induction motor 1. Reference numeral 8 denotes a voltage detector which detects and outputs a voltage between the R and S lines of the three-phase power lines R, S and T. Reference numeral 9 denotes a temperature detector which outputs a voltage signal corresponding to the temperature of the three-phase induction motor 1. Reference numeral 10 denotes an overload detection circuit which determines a reference rotation speed value in accordance with the outputs of the voltage detector 8 and the temperature detector 9, and determines that the startup has been completed based on the output of the rotation detector 7. The overload is determined and output according to the comparison result between the output 7 and the reference value.

An operation circuit 11 outputs a hoisting command signal 11U and a hoisting command signal 11D. Reference numeral 12 denotes an AC control circuit that changes the phase sequence of the voltages of the three-phase power supply lines R, S, and T supplied to the three-phase induction motor 1 in accordance with the hoisting command signal 11U and the hoisting command signal 11D from the operation circuit 11. Changes the rotation direction of the three-phase induction motor 1. Note that the lowering command signal 11
D is also input to the overload detection circuit 10.

Next, the operation of the motor overload detecting device for the hoist according to the first embodiment of the second invention will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 7 is a rotation speed characteristic diagram of the motor overload detection device of FIG. 6 during a hoisting operation. FIG. 3 is a characteristic diagram showing the relationship between the reference speed S0, the voltage, and the temperature at the time of the hoisting operation of the motor overload detecting device of FIG.

When a normal load equal to or less than the rated load is raised, the three-phase induction motor 1 is instantaneously accelerated by a large starting torque when started at time t1, so that the speed S3 temporarily exceeds the synchronous speed S2. After about t2, the speed settles to a speed S1 lower than the synchronous speed S2.

The overload detection circuit 10 detects the start of winding in response to the start of the voltage signal of the polarity indicating the winding rotation from the rotation detector 7 at time t1. Further, the overload detection circuit 10 outputs the voltage detected by the voltage detector 8,
The reference speed S0 at the time of hoisting is determined based on the temperature detected by the temperature detector 9. The reference speed S0 depends on the temperature and the voltage, and the speed S0 corresponding to the temperature T2 and the voltage V1 is shown in FIG. The temperature T1, temperature T2, and temperature T3 indicate high, medium, and low temperatures, respectively.

Further, at time t2, the overload detection circuit 10 determines that the start of the three-phase induction motor 1 has been completed in response to the output of the rotation detector 7, and then determines the rotation speed detected by the rotation detector 7. Since S1 exceeds the reference speed S0, it is determined that the load is normal under the rating, and no output is generated.

On the other hand, when a heavy load exceeding the rated load is carried, the speed settles to a speed S4 lower than the reference speed S0. Therefore, the overload detection circuit 10 determines that the overload exceeds the rated load after determining that the winding start of the three-phase induction motor 1 is completed at time t2, generates an output, and holds this output. . When receiving the lowering command signal 11D from the operation circuit 11, the overload detection circuit 10 releases the holding of the output of the overload. Thus the worker after unloading the cargo to know to ensure that it is in the overload state can resume work by pressing the push winding-up button.

Next, a second embodiment of the second invention of the present invention will be described with reference to FIG. In the motor overload detecting device according to the second embodiment of the second invention, the lowering command signal 11D of the operation circuit 11 is not input to the overload detecting circuit 10. Other configurations are the same as those of the first embodiment of the second invention.

The operation of the motor overload detecting device for the hoist according to the second embodiment of the second invention will be described with reference to FIG. The overload detection circuit 10 of this embodiment determines the rotation direction of the three-phase induction motor 1 based on the output polarity of the rotation detector 7 and determines whether or not the operation is the lowering operation. When the overload detection circuit 10 determines from the output of the rotation detector 7 that the three-phase induction motor 1 is performing the lowering operation, it releases the holding of the overload output. Therefore, the overload detection circuit 10 is
It does not require the lowering command signal 11D from. Other operations are the same as those of the first embodiment of the second invention.

Next, a third embodiment of the second invention of the present invention will be described with reference to FIG. In this embodiment, reference numeral 7 denotes a rotation detector comprising an AC tachometer, which outputs a voltage signal having a magnitude corresponding to the rotation speed of the three-phase induction motor 1. In this case, the output of the rotation detector 7 does not include information on the rotation direction of the three-phase induction motor. Other configurations are the same as those of the second embodiment of the second invention.

The operation of the third embodiment of the second invention will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 9 is a characteristic diagram showing the relationship between the load and the steady-state rotation speed after the start is completed in the case of the hoisting operation and the lowering operation. As can be seen from this figure, the stable speed SND during the hoisting operation is higher than the stable speed SNU during the hoisting operation. Therefore, when the rotation speed of the three-phase induction motor 1 is detected by the rotation detector 7 and the rotation speed is equal to or higher than the minimum value of the stable speed SND in the lowering operation of the three-phase induction motor 1, overload detection is performed. The circuit 10 determines that the three-phase induction motor 1 is performing the lowering operation, and releases the holding of the overload output. As described above, according to the third embodiment of the second invention, it is possible to determine the lowering operation state from the output of the rotation detector 7 that does not include the rotation direction information of the three-phase induction motor 1, and cancel the overload output. .

Next, a description will be given of a motor overload detecting apparatus for a hoist according to a fourth embodiment of the second invention with reference to FIG. In this embodiment, a hoisting command signal 11U is input from the operation circuit 11 to the overload detecting circuit 10 instead of the hoisting command signal 11D. Other configurations are the second
This is the same as the first embodiment of the invention.

The operation of the motor overload detecting device for the hoist according to the fourth embodiment of the second invention will be described with reference to FIG.
When the hoisting command signal 11U is no longer input from the operation circuit 11, the overload detection circuit 10 determines that the operation has stopped, and releases the holding of the overload output of the overload detection circuit 10. Therefore, immediately after stopping the three-phase induction motor 1, the hoisting operation can be restarted. Other operations are the same as those of the first embodiment of the second invention.

Next, a description will be given of a motor overload detecting device for a hoist according to a fifth embodiment of the second invention with reference to FIG. In this embodiment, the hoisting command signal 11U and the hoisting command signal 11D of the operation circuit 11 are
Not input to 0. Other configurations are the same as those of the fourth embodiment of the second invention.

The operation of the fifth embodiment of the second invention will be described with reference to FIG. When the rotation speed of the three-phase induction motor 1 is detected by the rotation detector 7 and the value falls below a predetermined value,
Alternatively, when it becomes 0, it is determined that the operation has been stopped, and the overload detection circuit 10 releases the holding of the overload output. Therefore, in the case of this embodiment, the overload detection circuit 10 does not need the hoisting command signal 11U from the operation circuit 11. Other operations are the same as in the fourth embodiment of the second invention.

In each of the above embodiments, the rotation detector 7 is constituted by a tacho generator, but may be constituted by a rotary encoder or the like. The voltage detector 8 detects the voltage between the power supply lines R and S, but may detect another line voltage.

Further, in each of the above embodiments, the case where the power supply is a commercial power supply and the frequency is constant has been described. However, when the induction motor is driven by using a variable voltage and variable frequency inverter, for example, the inverter may be driven by an inverter. The same effect can be obtained by detecting the output voltage, the output frequency, and the temperature of the motor to determine a reference rotation speed and comparing the reference rotation speed with the rotation speed of the induction motor.

[0044]

As described above, the motor overload detection device for a hoist according to the first invention of the present invention determines the reference speed value of the induction motor based on the detection values of the voltage detector and the temperature detector. Determines and determines the overload state of the induction motor based on the rotation speed detected by the rotation detector and this reference speed, so it does not require a complicated and expensive power detector, delay relay, and has a simple configuration. The overload state of the induction motor can be determined not only during the hoisting operation but also during the lowering operation.

As described above, according to the second aspect of the present invention, the overload state during the hoisting operation is detected by the motor overload detecting device having a simple configuration, and the operation is continued until the hoisting operation is stopped or the lowering operation is started. Since the output indicating the overload state is held, an inexpensive and easy-to-use motor overload detection device for the hoist can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a motor overload detection device according to a first invention of the present invention.

FIG. 2 is a rotation speed characteristic diagram during a hoisting operation of the motor overload detection device of FIG.

FIG. 3 is a characteristic diagram showing a relationship between a reference speed, a voltage, and a temperature at the time of a hoisting operation of the motor overload detection device of FIG.

FIG. 4 is a rotation speed characteristic diagram of the motor overload detection device of FIG. 1 during a lowering operation.

FIG. 5 is a characteristic diagram showing a relationship between a reference speed, a voltage, and a temperature during a lowering operation of the motor overload detection device in FIG.

FIG. 6 is a circuit diagram of a motor overload detection device according to a first embodiment of the second invention of the present invention.

FIG. 7 is a rotation speed characteristic diagram of the motor overload detection device of FIG. 6 during a hoisting operation.

FIG. 8 is a circuit diagram of a motor overload detection device according to second, third, and fifth embodiments of the second invention of the present invention.

FIG. 9 is a characteristic diagram showing a relationship between a load and a stable rotation speed after start-up is completed in a motor overload detection circuit according to a third embodiment of the second invention of the present invention for a hoisting operation and a lowering operation. .

FIG. 10 is a circuit diagram of a motor overload detection device according to a fourth embodiment of the second invention of the present invention.

FIG. 11 is a circuit diagram of a conventional motor overload detection device for a hoist.

12 is an operation characteristic diagram showing a relationship between voltage and power of the motor overload detection device in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Three-phase induction motor 2 Power detector 3 Converter 4 Comparator 5 Discrimination circuit 6 Overload detection circuit 7 Rotation detector 8 Voltage detector 9 Temperature detector 10 Overload detection circuit 11 Operation circuit 11U Winding command signal 11D winding Lower command signal 12 AC control circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H02P 7/36 302 H02P 7/36 302S

Claims (2)

(57) [Claims] A rotation detector that detects a rotation speed of an induction motor of a hoist; a temperature detector that detects a temperature of the induction motor; a voltage detector that detects a voltage applied to the induction motor; Reference speed determining means for determining a reference rotation speed of the induction motor in response to a temperature detection value detected by the temperature detector and a voltage detection value detected by the voltage detector; and a rotation speed detected by the rotation detector. A motor overload detecting device for a hoist, comprising: a determination unit configured to determine an overload of the induction motor based on the reference rotation speed determined by the reference speed determination unit. 2. A rotation detector for detecting a rotation speed of an induction motor of a hoist; a temperature detector for detecting a temperature of the induction motor; a voltage detector for detecting a voltage applied to the induction motor; Reference speed determination means for determining a reference rotation speed of the induction motor based on the temperature detection value detected by the temperature detector and the voltage detection value detected by the voltage detector; and detecting the rotation detector during the hoisting operation. When the rotation speed is lower than the reference rotation speed determined by the reference speed determination unit, an overload determination unit that determines an overload of the induction motor, and an output of the overload determination unit is held to perform the hoisting operation. A motor overload detecting device for a hoist, comprising: output holding means for canceling holding of the output of the overload determining means in response to a stop or a start of a lowering operation.