JPH072979U - Three-phase motor controller - Google Patents

Abstract

(57) [Summary] [Purpose] To reliably prevent the burnout of a three-phase motor due to a missing phase. [Structure] The magnitude of the R-phase current is determined by the current transformer 52.
Detected by A, the magnitude of the T-phase current is detected by the current transformer 5.
Detect at 2B. The current transformer 52A and the current transformer 52B are connected to the control circuit 50. Either one of the R-phase current value and the T-phase current value is a predetermined value (the motor 32
150% of the rated value of is for a predetermined time (5
If it continues for more than a second), the current passed through the motor 32 is set to zero and the motor 32 is stopped. When the T phase or the S phase is out of phase, the current value of the R phase exceeds the predetermined value for a predetermined time or more, and when the R phase is out of phase, the current value of the T phase exceeds the predetermined value. Since it continues for a predetermined time or longer, it can be determined that the control circuit 50 is in the open phase state regardless of which phase is open.
Can be reliably prevented from burning.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a control device for a three-phase motor that can prevent a three-phase motor from burning due to a missing phase.

[0002]

[Prior art]

 Grain dryers are used to dry grains. A grain tank for storing grains is formed inside the grain drying device, and a drying section for performing a drying process is formed below the grain tank. In the drying section, a downflow path is formed, which is partitioned by mesh partition walls. An air guide passage and an exhaust passage are formed adjacent to the downflow passage. A burner is connected to the air duct, and a suction fan is connected to the air duct.

A discharge port is provided at the lower end of the downflow path, and a shutter drum is arranged below the discharge port corresponding to the discharge port. Below the shutter drum, a lower screw conveyor that horizontally conveys grain toward the side of the machine is arranged, and on the discharge side of the lower screw conveyor, a bucket conveyor that conveys grain upward is arranged. An upper screw conveyor that horizontally conveys grains is arranged on the discharge side of the bucket conveyor, and the upper screw conveyor discharges the grains discharged from the bucket conveyor into the grain tank from the upper part of the grain tank.

When performing a drying process in the grain drying apparatus, a shutter drum, a lower screw conveyor, a bucket conveyor, an upper screw conveyor and the like are driven by a motor. As a result, the grain in the grain tank is fed out after being accommodated in the container of the shutter drum by a predetermined amount through the flow path. Grains fed from the feeding section are conveyed toward the side of the machine by the lower screw conveyor, and are conveyed above the machine by the bucket conveyor. Grains transported above the machine are discharged into the grain tank by the upper screw conveyor. In this way, the grain is circulated multiple times in the grain tank by the lower screw conveyor, bucket conveyor, upper screw conveyor, etc., and dried.

A three-phase AC motor is used as a motor for driving the lower screw conveyor, the bucket conveyor, and the upper screw conveyor. In order to prevent a failure due to overload, as shown in FIG. The current flowing in one phase (for example, R phase) is detected by the current sensor 102, and the current flowing to the motor 100 is set to zero when the current value exceeds the predetermined current value for a predetermined time or more. The motor 100 is prevented from being damaged.

[0006]

[Problems to be solved by the device]

 By the way, when one of the three phases is open, more overcurrent than the rated value flows in the other two phases.

However, in the related art, when the state in which the current value of the phase connected to the current sensor 102 exceeds the predetermined current value continues for a predetermined time or longer, the current flowing to the motor 100 is set to zero. In order to control 100, when the phase connected to the current sensor 102 is open phase (that is, when the current value becomes zero), the overcurrent of the other phase (S phase, T phase) cannot be detected. The motor 100 may be burned out.

The present invention has been made in consideration of the above facts, and an object of the present invention is to provide a control device for a three-phase motor that can reliably prevent burnout of the three-phase motor.

[0009]

[Means for Solving the Problems]

 The control device for a three-phase motor of the present invention comprises a first current detecting means for detecting the magnitude of a current flowing in any one of the three phases of the three-phase motor, and the first current detecting means. A second current detecting means for detecting the magnitude of the current flowing in any one of the remaining two phases in which the magnitude of the current is not detected, and the current detected by the first current detecting means. Control means for limiting the current flowing through the three-phase motor when at least one of the magnitude of the current and the magnitude of the current detected by the second current detecting means exceeds a predetermined value. And are characterized by having.

[0010]

[Action]

 In a three-phase motor, when one of the three phases is missing, a current larger than the rated current flows in the remaining two phases. In the control device for a three-phase motor of the present invention, for example, if 150% of the rated current of the three-phase motor is set as a predetermined value, the phase in which the magnitude of the current is detected by the first current detection means is determined. When the phase is lost, the magnitude of the current flowing in the remaining two phases exceeds a predetermined value, so an overcurrent is detected by the second current detection means, and the control means limits the current flowing through the three-phase motor to limit the three-phase motor. It is possible to prevent the motor from burning out.

On the other hand, when the phase in which the magnitude of the current is not detected by the first current detecting means is missing, the magnitude of the current in the phase in which the magnitude of the current is detected by the first current detecting means is predetermined. Since the value exceeds the value, the overcurrent is detected by the first current detecting means, and the control means can prevent the burnout of the three-phase motor by limiting the current flowing through the three-phase motor.

Therefore, the control device for a three-phase motor of the present invention can reliably prevent burnout of the three-phase motor regardless of which phase is missing.

[0013]

【Example】

 Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3 show a grain drying device 10 to which a control device for a three-phase motor of the present invention is applied.

The body 12 of the grain drying device 10 has a box shape that is high in the vertical direction and long in the front and back. The upper inner cavity of the airframe 12 is a grain tank 14, and the lower inner cavity is a drying section 16.

As shown in FIG. 2, the drying section 16 is formed with a flow-down path 18 partitioned by a porous wall or a mesh-shaped partition so that the grains in the grain tank 14 flow down. An air guide passage 20 and an exhaust passage 22 are alternately formed between the adjacent flow passages 18. A burner 24 is connected to the air guide passage 20, and a suction / exhaust fan 27, which is a blower system, is connected to the exhaust passage 22. Therefore, the hot air generated by the burner 24 is sent to the air guide passage 20 and flows from the air guide passage 20 through the downflow passage 18 to the exhaust passage 22. Therefore, the hot air dries the grain in the downflow passage 18. A discharge port 23 is provided at the lower end of the downflow path 18. Below the discharge port 23, a shutter drum 30 which is a feeding unit is arranged corresponding to the discharge port 23.

As shown in FIG. 3, the shutter drum 30 is formed in a substantially cylindrical shape, and a housing portion 30C is formed inside (see FIG. 2). The circumferential surface is provided with a slit-shaped opening 30A extending from the central portion in the longitudinal direction to one end. An opening 30B extending from the central portion in the longitudinal direction to the other end is also provided at a position that is moved 180 ° about the axis from the position where the opening 30A on the circumferential surface is provided.

The shutter drum 30 is provided with shafts 30 D and 30 E that project from both ends in the axial direction, and is rotatably supported by the machine body 12. The shutter drum 30 accommodates the grain stored in the downflow passage 18 in the accommodating portion 30C with the opening 30A or 30B positioned at the first position corresponding to the discharge port 23, and the opening 30A or 30B is disposed immediately below. The grain stored in the storage portion 30C in the state of being in the facing second position is fed downward.

The shutter drum 30 is fixed to the rotation shaft of the first motor 28 via a shaft 30D. The first motor 28 reciprocally rotates the shutter drum 30 between the first position and the second position. In addition, two limit switches (not shown) are installed near the shutter drum 30. Each of the limit switches is connected to the input / output port 50D of the control circuit 50 that constitutes a part of the control means, and the position of the shutter drum 30 is the first position and the second position where the shutter drum 30 is stopped. It is detected whether or not the position is.

Below the shutter drum 30, a lower screw conveyor 34 driven by a motor 32 as a second motor is arranged. The lower screw conveyor 34 constitutes a part of the discharging section and conveys the grain fed by the shutter drum 30 to the front side of the machine body 12.

A bucket conveyor 36 is erected on the front side of the machine body 12. The inside of the bucket conveyor 36 is composed of an endless conveyor 39 driven by a motor 38 and a grain carrying bucket 41 attached to the endless conveyor 39.

As shown in FIGS. 2 and 3, the bucket conveyor 36 conveys the grain fed from the lower screw conveyor 34 to the uppermost portion of the machine body 12. One end of the upper screw conveyor 40 corresponds to the upper end of the bucket conveyor 36, and the rotary equalizer 42 is connected to the other end of the upper screw conveyor 40. The upper screw conveyor 40 and the rotary equalizer 42 are driven by the motor 38 together with the bucket conveyor 36, and the rotary equalizer 42 transfers the grain conveyed by the upper screw conveyor 40 to the grain tank of the machine body 12. Radiation distribution to 14 is made.

A grain discharge passage 80 is provided below one end of the upper screw conveyor 40, and an opening / closing shutter 82 driven by a motor (not shown) is arranged in the grain discharge passage 80. There is. The opening / closing shutter 82 closes the grain discharge passage 80 during the grain drying operation, but moves to the state where the grain discharge passage 80 is opened during the grain discharge operation.

A thrower 92 driven by a motor (not shown) is connected to the grain discharge path 80. The thrower 92 further separates the grain discharged outside the machine body 12 from the machine body 12 via the grain discharge path 80. It is transported to a position (particularly a position higher than the machine body 12).

As shown in FIG. 4, the motor 32 that drives the lower screw conveyor 34 is connected to a three-phase power source (not shown) via a drive circuit 58 that forms part of the control means. The drive circuit 58 is connected to the input / output port 50D of the control circuit 50, and the drive circuit 58 drives the motor 32 by a signal from the control circuit 50.

Although illustration is omitted, the first motor 28, the motor 38, and the motors for driving the opening / closing shutter 82 are also control circuits via the drive circuits connected to the power sources in three phases similarly to the motor 32. Connected to 50.

In the motor 32, any two phases, in this embodiment, the R phase is connected to the current transformer 52A as a current detecting means, and the T phase is connected to the current transformer 52B. The current transformer 52A is connected to the input / output port 50D of the control circuit 50 via the filter 53A, the rectifier 54A, and the AD converter 56A. The filter 53A removes noise of the signal (analog signal) output from the current transformer 52A, the rectifier 54A rectifies the signal passed through the filter 53A, and the AD converter 56A converts the analog signal into a digital signal. Output to the control circuit 50. Similarly, the current transformer 52B is connected to the input / output port 50D of the control circuit 50 via the filter 53B, the rectifier 54B, and the AD converter 56B. A stop switch 64 is connected to the input / output port 50D of the control circuit 50. When the stop switch 64 is turned on, the first motor 28, the motor 32, the motor 38, and the motor 81 of the grain drying device 10 are stopped. Then, the discharging process is stopped.

The control circuit 50 includes a CPU 50A, a ROM 50B, a RAM 50C, and an input / output port 50D, which are connected to each other by a bus.

It should be noted that in the present embodiment, the control circuit 50 determines that one of the magnitude of the R-phase current and the magnitude of the T-phase current of each motor is a predetermined value (in the present embodiment, the rated current (150%) and exceeds the predetermined value for 5 seconds or more, it is determined that the motor is in the open phase state and the current flowing to the open phase motor is set to zero. Control 58.

Next, the operation of this embodiment will be described. When performing the drying process in the grain drying device 10, the shutter drum 30, the lower screw conveyor 34, the bucket conveyor 36, the upper screw conveyor 40, and the rotary type leveling machine 42 are driven. As a result, the grain in the grain tank 14 is fed out after being accommodated in a predetermined amount in the accommodation portion 30C of the shutter drum 30 via the flow-down path 18. The fed-out grain is conveyed to the side of the machine body by the lower screw conveyor 34, and is conveyed to the upper side of the machine body by the bucket conveyor 36. The grain conveyed above the machine body is discharged into the grain tank 14 by the upper screw conveyor 40. In this way, the grain is circulated in the grain tank a plurality of times by the lower screw conveyor 34, the bucket conveyor 36, the upper screen conveyor 40, etc., and dried.

Next, the processing when the motor of the grain drying device 10 is out of phase will be described with reference to the flowchart of FIG. Although the present embodiment will be described below by taking numerical values that do not hinder the present invention as an example, the present invention is not limited to these numerical values.

In step 100, the R-phase current value I _R is fetched, then the process proceeds to step 102, the T-phase current value I _T is fetched, and the process proceeds to step 104.

In step 104, it is determined whether or not the R-phase current value I _R exceeds a predetermined value (150% of the rated value in this embodiment). When the current value I _R exceeds the predetermined value, the routine proceeds to step 106, the timer 1 is started, and the routine proceeds to step 108.

In step 108, it is determined whether or not the timer 1 is 5 seconds or more. If it is 5 seconds or more, the process proceeds to step 110, the current flowing through the motor is set to zero, and the motor is stopped. An alarm may be sounded when the motor is stopped. If it is less than 5 seconds, the process returns to step 100.

If the timer 1 has already started, no processing is performed in step 106.

On the other hand, in step 104, when the R-phase current value I _R is less than or equal to the predetermined value, the process proceeds to step 112, where the T-phase current value I _T is the predetermined value (150% of the rated value in this embodiment). ) Is exceeded. If the current value I _T exceeds the predetermined value, the process proceeds to step 114 to start the timer 2 and proceeds to step 116. In step 116, it is determined whether or not the timer 2 is 5 seconds or more. If it is 5 seconds or more, the process proceeds to step 110, the current flowing through the motor is made zero, and the motor is stopped. If the timer 2 is less than 5 seconds, the process returns to step 100.

On the other hand, if the T-phase current value I _T is less than or equal to the predetermined value in step 112, the process proceeds to step 118, the timers 1 and 2 are reset, and the process returns to step 100. If the timer 1 has already been reset, the timer 1 is not reset in step 118, and if the timer 2 has already been reset, no processing is performed in step 118.

If the timer 2 has already started, no processing is performed in step 114.

As described above, when the R phase is missing, the current flowing in the T phase and the S phase becomes larger than the rated value and exceeds the predetermined value. When the time over the predetermined value exceeds the predetermined time, the control device 50 determines that the motor is in the open phase state, the current flowing to the open phase motor is set to zero, and the motor burnout is prevented.

Further, when the T phase is out of phase, the current flowing in the R phase and the S phase becomes larger than the rated value and exceeds a predetermined value. When the time over the predetermined value exceeds the predetermined time, the control device 50 determines that the motor is in the open phase state, and the current flowing through the open phase motor is set to zero to prevent the motor from being burned.

Further, when the S phase is missing, the current flowing in the T phase and the R phase becomes larger than the rated value and exceeds a predetermined value. When the time over the predetermined value exceeds the predetermined time, the control device 50 determines that the motor is in the open phase state, and the current supplied to the open phase motor is set to zero to prevent the motor from being burned.

Therefore, in the present embodiment, the current flowing through the motor is made zero when any of the phases is lost, so that the motor is reliably prevented from burning.

In the present embodiment, an example in which the present invention is applied to the grain drying device 10 has been shown, but the present invention may be applied to a motor of equipment other than the grain drying device 10.

[0043]

[Effect of device]

 As described above, the control device for a three-phase motor according to the present invention has the above-described structure, and therefore has an excellent effect that the burnout of the three-phase motor due to a missing phase can be reliably prevented.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a grain drying device.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a perspective view showing a configuration of each drive device arranged in the grain drying device.

FIG. 4 is a schematic block diagram showing connections around a control circuit.

FIG. 5 is a flowchart illustrating the operation of this embodiment.

FIG. 6 is a wiring diagram showing connections around a control circuit of a conventional grain drying device.

[Explanation of symbols]

 32 motor (three-phase motor) 50 control means (control circuit) 52A current transformer (first current detection means) 52B current transformer (second current detection means)

Claims (1)

[Scope of utility model registration request] 1. A first current detection means for detecting a magnitude of a current flowing in any one of the three phases of a three-phase motor; and a magnitude of the current detected by the first current detection means. Second current detecting means for detecting the magnitude of the current flowing in any one of the remaining two phases that are not blocked, and the magnitude of the current detected by the first current detecting means and the second current detecting means. Control means for limiting the current flowing through the three-phase motor when at least one of the magnitudes of the currents detected by the current detection means exceeds a predetermined value. Phase motor control device.