JP2020171187A - Overload protective relay and mcc unit - Google Patents

Abstract

To provide an overload protective relay for cutting off a load current with higher accuracy when an overload is detected in a load current of a motor.SOLUTION: An overload protective relay 30 includes a current sensor 36 for measuring a load current applied to a motor 5 through an electric circuit and converting the measured load current into an electric signal and outputs it, and a drive control unit 42, to which the electric signal output from the current sensor 36 is input, for driving a magnetic contactor 20 to cut off the load current applied to the motor 5 when a load current value based on the input electrical signal exceeds a predetermined threshold.SELECTED DRAWING: Figure 3

Description

The present invention relates to an overload protection relay for an induction motor and a motor control center (MCC) unit including the relay.

According to the results of a survey conducted by the Resources and Energy Agency in 2009, three-phase induction motors are used in various applications such as pumps, blowers, and compressors in the industrial sector, and the power consumption is the industrial sector in Japan. It accounts for 75% of the total power consumption of Japan and about 55% of the total power consumption of Japan, and is a device that consumes a considerable amount of energy.
Source: Ministry of Economy, Trade and Industry "Current status of three-phase induction motors"
(Http://www.meti.go.jp/committee/sougouenergy/shou_energy_kijun/sansou_yudou/001_04_00.pdf)
In addition, as the current state of the domestic market for three-phase induction motors (Source: Ministry of Economy, Trade and Industry Production Dynamics Statistics (FY2008)), three-phase induction with respect to the production and shipment results (FY2008) capacity (MW) of motors in FY2008. It is shown that electric motors account for 83%. Therefore, improving the efficiency of three-phase induction motors will greatly contribute to energy saving in Japan.

From April 2015 onward, the energy consumption efficiency of motors including three-phase induction motors shipped domestically must not fall below the standard energy consumption efficiency, weighted by the number of units shipped for each category. In advancing these, the efficiency classification of three-phase induction motors is defined by IE1 (standard efficiency), IE2 (high efficiency), and IE3 (premium efficiency), and the IE3 motor with the highest efficiency is also called the top runner motor. There is.
A motor (induction motor) is a machine that converts electrical energy into mechanical energy, and a part of it is consumed inside the motor as thermal energy during energy conversion. The energy that is consumed inside and cannot be used as power is a loss, and if the loss is large, the output to the motor input becomes small, and wasteful power is consumed. The ratio of this input to output is the efficiency of the motor.

The loss generated by the motor can be divided into fixed loss (iron loss and mechanical loss), load loss (primary copper loss and secondary copper loss), and stray load loss. Of these, iron loss is a loss that occurs with a change in the magnetic field of a magnetic circuit. Mechanical loss includes loss due to frictional resistance between the rotor and stator bearings, wind loss of the cooling fan, and the like. Copper loss is the loss of electrical energy that replaces thermal energy due to the electrical resistance in the wires of the copper winding.
The primary copper loss occurs in the stator conductor, and the secondary copper loss occurs in the rotor conductor. The drifting load loss is a loss other than the above. In the breakdown example of each generated loss of the motor, of the total loss during rated operation, the primary copper loss is 40%, the iron loss is 30%, the secondary copper loss is 16%, the mechanical loss is 12%, and the stray load loss is. There are also reports such as 2%.

Therefore, as a method of improving the efficiency of the motor, reduction of copper loss, which accounts for a large proportion of the loss of the motor, is being carried out. By increasing the cross-sectional area of the coil winding to suppress the copper loss in order to reduce the copper loss, in the above example, the loss due to the copper loss corresponding to 56% of the total loss is reduced. ing. Therefore, the starting current of the motor increases in order to maintain the drive torque required to accelerate the rotation from the start of the motor to the rated operating state.
On the other hand, power is supplied to the three-phase induction motor from the original power supply source via a molded case circuit breaker (also referred to as MCCB, MCB, breaker), an electromagnetic contactor (MC), or a thermal relay. Circuit breakers for wiring, electromagnetic contacts, and thermal relays are also collectively called MCC units, and are made by combining a circuit breaker for wiring that protects a short circuit of a three-phase induction motor and a thermal relay that is a protective relay against overload of the motor. Appropriate motor protection coordination is in place.

The thermal relay as an overload protection relay uses an element that combines a bimetal and a heater. For example, the load current of the motor is converted into heat by a heater to heat the bimetal to bend the bimetal, and the bending displacement of the bimetal causes the bimetal to bend. It is a mechanism that detects current and protects the motor against overcurrent due to overload. Therefore, it is called a thermal overload protection relay.
The operating current value of the thermal relay is set by dialing like a mechanical thermostat, and normally the 3-pole product has a heater only at both ends. The current settling value is set to 1.73 times or less of the normal value with the motor load, ensuring the safety of the system in an analog manner.

By the way, in motors such as three-phase induction motors, the shift to top runner motors (IE3) with improved efficiency during operation is progressing. The top runner motor has a structure that increases the cross-sectional area of the coil winding to suppress copper loss as a means of increasing efficiency, so it is more efficient and energy efficient than conventional motors (IE1, IE2), but the starting current is large. ..
On the other hand, since the existing MCC unit is selected according to the conventional motor, when the top runner motor is applied, the molded case circuit breaker and thermal relay may not be required due to the starting current, and the top runner motor may not be able to start. There is sex. Therefore, it is necessary to perform appropriate protection coordination according to the characteristics of the Top Runner motor.

Therefore, in Patent Document 1, the contact is opened and closed by two bending displacements of the auxiliary bimetal, which bends in the direction opposite to the bending direction of the bimetal due to the temperature rise inside the case, and the bimetal and the auxiliary bimetal, as compared with the conventional thermal relay. We are proposing a thermal relay that does not displace even when the starting current increases by applying a top runner motor with improved efficiency by having a configuration with an inversion mechanism that inverts.

JP-A-2017-195111

However, the thermal relay moves the bimetal by the thermal energy generated by the bimetal and the electric current flowing through the heater. The thermal energy due to the increase in the starting current of the Top Runner motor is proportional to the square of the current flowing through the heater. Therefore, it cannot be said that the time for the bimetal to move is strictly controlled by the thermal energy due to the increase in the starting current for the conventional motor. That is, the thermal relay operates the cutoff process faster by the amount of the increase in the thermal energy converted from the current with respect to the increase in the current. Therefore, in Patent Document 1, an auxiliary bimetal that operates in the direction opposite to that of the main bimetal is mounted, and the influence of the starting current of the motor is affected by the bimetal in order to avoid unnecessary operation (mistrip) of power supply to the motor. It can be said that it is delayed.

In addition, the thermal relay cannot ignore the power loss due to the heat of the heater wound around the bimetal. If there is no power loss here, the power that can be supplied to the motor can be further improved. In addition, circuit breakers due to the influence of inrush current when the motor is started are handled by a molded case circuit breaker.
The present invention has been made in view of such conventional problems, and an object of the present invention is to cut off the load current with higher accuracy when an overload is detected in the load current of the electric motor. It is an object of the present invention to provide a possible overload protection relay and an MCC unit equipped with the relay.

In order to achieve the above object, the overload protection relay according to one aspect of the present invention measures a load current applied to an electric motor through an electric circuit, converts the measured load current into an electric signal, and outputs a current sensor and a current sensor. A drive control unit that inputs the electric signal output from the motor and drives the electromagnetic contactor to cut off the load current applied to the electric motor when the load current value based on the input electric signal exceeds a predetermined threshold. It has.

Further, the MCC unit according to one aspect of the present invention includes the overload protection relay, a molded case circuit breaker for opening and closing the electric circuit, and an electromagnetic contactor.

Further, the MCC unit according to one aspect of the present invention includes a molded case circuit breaker and an electromagnetic contactor having the overload protection relay, an opening / closing part for opening / closing the electric circuit, and a drive control part for controlling the opening / closing of the opening / closing part. And have. Then, the drive control unit of the overload protection relay converts the starting current value and rated current value of the electric motor measured by the current sensor into a digital value, and the digital value data converted by the converter for each starting current value. It is provided with a processing device for processing and a storage unit for storing the starting current value and the rated current value processed by the processing device. Each drive control unit of the molded case circuit breaker and the magnetic contactor is provided with a digital processing device having digital processing and communication functions. The MCC unit further includes a transmission system that transmits data stored in the storage unit of the overload protection relay to each drive control unit of the molded case circuit breaker and the magnetic contactor by serial communication.

The point is to be able to directly measure the current value flowing through the main circuit. If at least a part of the electric power consumed by the bimetal is used, the current measurement of the main circuit and the processing operation as a thermal relay by the measured current value, that is, the steady operation excluding the large current period at the time of starting the motor. It is possible to detect the overload of the motor flowing through the main circuit at the time and to cut off the main circuit based on the overload detection.
The power consumed by the bimetal is proportional to the square of the current flowing through the bimetal. Immediately before the electromagnetic contactors that make up the MCC unit start and the motor (motor) starts, the power consumed by the bimetal is zero, but until the rotation speed of the motor reaches the rated operation, the rotation of the motor is accelerated. The required torque is excited, and the torque required for this rotational acceleration reaches the maximum at a certain appropriate rotation speed up to the rated rotation speed, and then decreases to the rated rotation speed.

The starting current required when starting the motor is the inductance component required to generate rotational torque and the admittance component required to magnetically excite the motor, and the current flowing through the inductance component is the increased current flowing when the motor is started. I can think.
Therefore, if a means for measuring the starting current flowing when the motor is started is provided, and a means for accurately measuring a relatively small current in a state where the motor is in the rated operating operation state after the start is provided, the motor It is possible to digitize the motor starting current change process that flows at the time of starting, and in addition, it is possible to digitize the current change of the rated current when the motor is in the rated operating state after starting. ..

Data conversion of the motor operating process such as the above current leads to digital realization of failure prediction from the tendency of changes in the operating state of the installed motor, assuming long-term use of the motor. At the same time, power saving can be realized.
In addition, by configuring a system for sharing information through serial communication, such as digitizing wiring breakers, magnetic contactors, and overload protection relays in the MCC unit, for example, the magnetic contactor mainly supplies power. The circuit voltage drive information can be shared with the overload protection relay, and the overload protection relay can share the current value information flowing through the main circuit with the magnetic contactor, and the current operating operation of the motor can be shared with the higher system of the MCC unit. In addition to the state information, information on changes in the operating state over a long period of time can be shared, and the operating state of the motor and failure prediction information can be accurately monitored.

According to one aspect of the present invention, there is provided an overload protection relay capable of cutting off the load current with higher accuracy when an overload is detected in the load current of the electric motor, and an MCC unit including the overload protection relay. Can be done.

It is a figure which shows the MCC unit and the power supply system which provided the overload protection relay which concerns on 1st Embodiment of this invention. It is a system block diagram of the MCC unit of FIG. It is a block diagram of the overload protection relay of FIG. It is a figure which shows a part of the overload protection relay of FIG. 1 in detail. It is explanatory drawing of the general motor protection emphasis. It is a block diagram of the overload protection relay which concerns on 2nd Embodiment of this invention. It is a figure which shows a part of the overload protection relay of FIG. 6 in detail.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following embodiments, an overload protecting relay, an MCC unit including the relay, and a power supply system will be described.
In all the drawings for explaining the embodiment of the invention, those having the same function are designated by the same reference numerals, and the repeated description thereof will be omitted.
In addition, each drawing is schematic and may differ from the actual one. In addition, the following embodiments exemplify devices and methods for embodying the technical idea of the present invention, and do not specify the configuration to the following. That is, the technical idea of the present invention can be modified in various ways within the technical scope described in the claims.

(First Embodiment)
First, a power supply system for supplying power to the motor will be described with reference to FIG.
As shown in FIG. 1, the electric power supply system 1 supplies electric power from the electric power supply source 2 to the motor (electric motor) 5 via the MCC unit 3. Then, the MCC unit 3 is connected in series to the main circuit electric wire 4 as an electric circuit for electrically connecting the power supply source 2 and the motor 5, and is inserted in order from the power supply source 2 side. A device 20 and an overload protection relay 30 are provided. That is, the power is supplied to the motor 5 in the order of the power supply source 2, the molded case circuit breaker 10 of the MCC unit 3, the electromagnetic contactor 20, and the load protection relay 30.

Here, a general motor protection coordination will be described with reference to FIG. 5 (Source: Excerpt from the Web page of the Japan Electric Industry Association).
As shown in FIG. 5, in the motor, the starting current generated at the time of starting increases with respect to the rated current. This is due to the increase in the current that stores energy in the inductor of the motor and the current that is required to generate the torque of the motor. FIG. 5 shows an unnecessary operating area of the molded case circuit breaker and an unnecessary operating area of the thermal relay. The unnecessary operating region of the molded case circuit breaker is the current that stores energy in the above-mentioned inductor and the current that generates the starting torque of the motor. The unnecessary operating region of the thermal relay is the current that flows to generate the torque of the motor.

As shown in FIG. 5, the thermal characteristics of the motor show the current-time relationship that the motor can thermally withstand, and become anti-timed characteristics. In the case of a conventional motor, a starting current (effective conversion value) that is several times higher generally flows at the time of starting, and gradually converges to the rated current as the motor rotation speed increases. In order to protect the motor from overload, it is necessary to emphasize the protection by setting the operating characteristics of the thermal relay to be smaller than the thermal characteristics of the motor and not intersecting with the motor starting current. In the case of a top runner motor with improved efficiency during operation, the starting current tends to increase as shown in the hatched portion in FIG. For this reason, the dynamic characteristics of the thermal relay and the motor starting current may intersect, and the thermal relay may mistrip.
Although the thermal relay that is thermally controlled is described in FIG. 5, the overload protection relay 30 of the first embodiment electronically controls the thermal relay.

Next, a specific configuration of the power supply system 1 and the MCC unit 3 will be described with reference to FIG. This first embodiment is an example of a system in which the entire MCC unit is shown with respect to a power supply mode, an information linkage mode, and power system sensing in each unit. In addition, the power supply system 1 shown in FIG. 2 is an example for explaining the present invention, and is not limited to the power supply form, the information linkage form, and the sensing of the power system. For example, in the power system example, AC This is an example of configuring an internal circuit drive power supply by receiving power from the system, but for example, a system may be used in which power is supplied from the outside by USB (Universal Serial Bus) connection and at the same time serial communication is performed.

FIG. 2 is a diagram showing a sequence of power supply to be supplied to the motor, and is an example of a power supply system for supplying power from the power supply source 2 to the motor 5 by three-phase alternating current.
Power is supplied to the motor 5 in the order of the molded case circuit breaker 10, the magnetic contactor 20, and the overload protection relay 30 that make up the MCC unit 3.
The molded case circuit breaker 10 cuts off three-phase alternating current. Then, when the molded case circuit breaker 10 is closed, power is supplied to the magnetic contactor 20 via an internal switch.

The magnetic contactor 20 also opens and closes the contact portion by using the magnetic energy of the electromagnet by driving the internal control circuit 22a and the drive circuit 22b from the power supply supplied from the outside by the power supply circuit. In the initial state of the magnetic contactor 20, the contact portion is open, and the contact portion remains closed due to the magnetic force of the electromagnet.
After that, the current of the motor is supplied via the connected overload protection relay 30. The overload protection relay 30 constantly monitors the current, outputs a trip signal when a current exceeding an allowable current value flows through the motor, and cuts off the power supply system with the magnetic contactor 20.

Each of the molded case circuit breaker 10 and the magnetic contactor 20 has an opening / closing unit 11/21 for opening / closing the main circuit electric wire 4 as an electric circuit, and drive control units 12 and 22 for controlling the opening / closing of the opening / closing unit 11 and 21. I have. The opening / closing portions 11 and 21 include a contact portion inserted in series with the main circuit electric wire 4 and a coil portion for opening / closing the contact portion. The drive control units 12 and 22 include control circuits 12a and 22a and drive circuits 12b and 22b. Here, only the magnetic contactor 20 is opened and closed by the electromagnet. The molded case circuit breaker 10 generally closes manually, and in the case of an electronic principle, the trip coil is excited by a drive circuit to operate the contact portion. The control circuits 12a and 22a are composed of, for example, a digital processing device such as a microprocessor having a built-in storage unit and further having digital processing and communication functions.

As shown in FIG. 2, the overload protection relay 30 includes a current sensor 36 (indicated by ●) that measures the current value of the current flowing through the power supply system. As the current sensor 36, for example, in the case of AC, in addition to the current sensor by the magnetic sensor using the current transformer, the Rogowski coil, and the Hall element sensor, there is also a current sensing circuit using the shunt resistor, and any current sensor. It does not determine whether to do it. What is required is that insulation is required between the power supply system to the motor 5 and the drive control unit (drive circuit and control circuit), the communication system, and the external power supply.

The control circuit 42 of the overload protection relay 30 preferably includes, for example, a microprocessor (hereinafter referred to as MPU) as an arithmetic processing unit and an analog / digital converter (hereinafter referred to as ADC). Due to the ADC built in the MPU, the current value of the current supply system can be stored in the storage unit 101 (see FIG. 4) built in the MPU and the control circuit 42.
The instantaneous value data of the power supply system measured and stored by the overload protection relay 30 is transmitted to the control circuits 12a of the molded case circuit breaker 10 and the electromagnetic contactor 20 via the communication system 50 shown by the dotted line in FIG. Information can be shared with the MPU mounted on the control circuit 22a, for example, as serial communication.

Next, the specific configurations of the electromagnetic contactor 20 and the overload protecting relay 30 will be described with reference to FIGS. 3 and 4.
As shown in FIG. 3, the magnetic contactor 20 is connected to the internal power supply line Lp1 as an electric circuit, the first external terminal 28 connected to one end side of the internal power supply line Lp1, and the other end side of the internal power supply line Lp1. The second external terminal 29 is provided. Further, the electromagnetic contactor 20 includes an opening / closing portion 21.

The internal power supply line Lp1 is inserted in series with the main circuit electric wire 4 (see FIG. 1). The power supply source 2 side of the main circuit electric wire 4 is connected to the first external terminal 28, and the motor 5 side of the main circuit electric wire 4 is connected to the second external terminal 29. That is, the internal power supply line Lp1 constitutes a part of the main circuit electric wire 4, and the load current when the motor 5 is operating flows. The load current includes a rated current, a starting current, an inrush current, and the like. The second external terminal 29 of the magnetic contactor 20 is electrically connected to the first external terminal 31 of the overload protecting relay 30, which will be described later, via the main circuit electric wire 4.

The opening / closing section 21 includes a contact section 24 inserted in series with the internal power supply line Lp1 and a coil section 25 inserted in series with the coil power supply line 26 to drive the contact section 24 to open / close.
The contact portion 24 has a pair of fixed contacts (fixed contact portions) 24a and movable contacts (movable contact portions) 24c arranged so as to be contactable and detachable from the pair of fixed contacts 24a and 24b. .. The contact portion 24 is usually in an open state (off state) in which the movable contact 24c is separated from the pair of fixed contacts 24a and 24b. Then, the contact portion 24 maintains a closed state (on state) in which the movable contact 24c is in contact with the pair of fixed contacts 24a and 24b by the electromagnetic force of the electromagnet in the coil portion 25.

The coil portion 25 is inserted into the coil power supply line 26 in series. Then, the coil portion 25 switches the contact portion 24 from the open state to the closed state by exciting the electromagnet by the electric power supplied from the power source of the coil power supply line 26. Then, the coil portion 25 switches the contact portion 24 from the closed state to the open state when the power supply is cut off.
The opening / closing portion 33 of the overload protecting relay 30, which will be described later, is inserted into the coil power supply line 26 in series. The drive of the opening / closing unit 33 is controlled by the drive control unit 38 of the overload protecting relay 30. That is, the drive of the magnetic contactor 20 is controlled by the drive control unit 38 of the overload protection relay 30.

As shown in FIG. 3, the overload protection relay 30 is located on the internal power supply line Lp2 as an electric circuit, the first external terminal 31 connected to one end side of the internal power supply line Lp2, and the other end side of the internal power supply line Lp2. It is provided with a connected second external terminal 32. Further, the overload protection relay 30 includes an opening / closing portion 33 inserted in series with the coil power supply line 26, and a current sensor 36 inserted in series with the internal power supply line Lp2. Further, the overload protection relay 30 includes a power generation unit 37, a drive control unit 38, and a signal insulator 39.

The internal power supply line Lp2 is inserted in series with the main circuit electric wire 4 (see FIG. 1). Then, the power supply source 2 side of the main circuit electric wire 4 is connected to the first external terminal 31, and the motor 5 side of the main circuit electric wire 4 is connected to the second external terminal 32. That is, the internal power supply line Lp2 constitutes a part of the main circuit electric wire 4, and the load current when the motor 5 is operating flows. The first external terminal 31 of the overload protecting relay 30 is electrically connected to the second external terminal 29 of the magnetic contactor 20 via the main circuit electric wire 4.

The opening / closing portion 33 includes a contact portion 34 inserted in series with the coil power supply line 26, and a coil portion 35 for opening / closing the contact portion 34. The contact portion 34 comprises a pair of fixed contacts (fixed contact portions) 34a and 34b and a movable contact (movable contact portion) 34c arranged so as to be contactable and detachable from the pair of fixed contacts 34a and 34b. Have. The opening / closing portion 33 is normally in a closed state (on state) in which the movable contacts 33c are in contact with the pair of fixed contacts 34a and 34b, and is in a conductive state in which a current flows through the coil power supply line 26.

When an excessive current is detected in the power supply system that supplies electric power from the second external terminal 32 to the motor 5, the opening / closing unit 33 excites the coil by the electromagnetic force of the coil unit 35 to move the contact unit 34. And cut off the power supply system.
As shown in FIG. 3, the current sensor 36 measures the load current applied to the motor 5 through the internal power supply line Lp2, converts the measured load current into an electric signal, and outputs the measured load current. In this first embodiment, the current sensor 36 is shown as an example by a shunt resistor. With this shunt resistance, the load current flowing from the first external terminal 31 to the second external terminal 32 when power is supplied to the motor 5 can be detected as a voltage in the form of a product of the shunt resistance value and the current value. Of course, the current sensor 36 is not limited to the shunt resistance, but is described as a resistance type for the sake of simplicity.

As shown in FIG. 3, the power supply generation unit 37 includes a rectifier circuit 37A, a voltage detection circuit 37B, and a power supply circuit 37C. The rectifier circuit 37A converts the power supply 40 supplied from the outside into direct current by closing the switch 41 (on state), and the power supply voltage supplied by the voltage detection circuit 37B operates the internal circuit. Detect whether it is sufficient or not. In this first embodiment, although it is described by the AC symbol, it may be a direct current. If the power supply voltage is not sufficient to drive the internal control circuit 42, a measure may be taken to stop the operation of the MCC unit 3.

The power supply circuit 37C generates a power supply necessary for the control circuit 42 and the drive circuit (pulse generation circuit) 43 to operate from the voltage converted to direct current by the rectifier circuit 37A.
The drive control unit 38 includes a control circuit 42 and a drive circuit 43. The control circuit 42 is composed of, for example, an arithmetic processing device such as a microprocessor having a storage unit 101 shown in FIG. 4. The drive circuit 43 is composed of, for example, a pulse generation circuit.

The storage unit 101 is composed of a non-volatile storage device such as a ROM, and stores a control program that controls the operation of the control circuit 42. Further, the storage unit 101 stores data of a predetermined threshold value for the overload current applied to the motor 5 through the internal power supply line Lp2 when the motor 5 is started. In addition, the storage unit 101 stores a load current abnormality determination program for determining the presence or absence of an abnormality in the load current. When the load current value measured by the current sensor 36 exceeds a predetermined threshold value, the load current abnormality determination program determines that there is an abnormality, and the load current value measured by the current sensor 36 is predetermined. It is equipped with an abnormality determination function that determines "no abnormality" when it is below the specified threshold value. The load current abnormality determination program is provided with a drive command output function that outputs a drive command signal to the drive circuit 43 when the abnormality determination function determines that there is an abnormality.

Further, the storage unit 101 stores in advance a drive program pattern 102 that controls the drive (opening process) of the opening / closing unit 33. According to the stored drive program pattern 102, the coil of the coil unit 35 is excited by the drive circuit 43 by generating the drive power 46s, and the movable contacts 24c are separated from the pair of fixed contacts 34a and 34b (open state). Turn off). As a result, when an abnormal current is detected in the motor 5, the magnetic contactor 20 can cut off the main circuit electric wire 4, so that the function as a thermal relay can be achieved.

The signal insulator 39 is inserted in series with the signal line 44 that transmits the electric signal of the current sensor 36 (output side) to the control circuit 42 (input side) of the drive control unit 38, and is inserted in series with the current sensor 36 and the drive control unit. The signal is transferred while ensuring insulation from the control circuit 42 of 38.
The current sensor 36 measures the load current applied to the motor 5, converts the measured load current into an electric signal (current sensor signal), and outputs the measured load current to the signal line 44. The electric signal of the current sensor 36 is transmitted to the signal insulator 39 via the signal line 44. Then, the electric signal transmitted from the current sensor 36 to the signal insulator 39 is transmitted by the signal insulator 39 to the control circuit 42 of the drive control unit 38 via the signal line 44. The alternate long and short dash line in FIG. 4 shows the insulation required between the control circuit system and the power supply system as a system. As an example, the insulation between the power supply system including the contact portion 34 of the opening / closing unit 33 and the current sensor 36 and the control circuit system including the drive control unit 38 is shown.

As an example, the signal insulator 39 has a function of performing impedance conversion of a voltage signal detected on the current sensor 36 side by an appropriate operational amplifier and having analog / digital conversion. Since digitization is not an essential requirement, it is shown as an example in which the insulated part is simply realized by insulating the detected signal. In addition, since the signal insulator 39 is a commercially available device, it is described in the figure as a device that can easily realize an insulating function. Of course, insulation by analog signals is also feasible. Further, although not shown, a power supply function for supplying power to the current sensor 36 side of the signal insulator 39 is required.

The current sensor signal 44s insulated by the signal insulator 39 is input to the control circuit 42 of the drive control unit 38 via the signal line 44. The voltage signal detected by the current sensor 36 is a current measurement pattern 103 stored in the storage unit 101 in the control circuit 42 to magnetically excite the motor 5 after the power supply system to the motor 5 is supplied. The start current is supplied to the inductor component that generates the admittance component and motor torque and is involved in driving.
When the motor 5 reaches the rated operation, the rotational acceleration is no longer necessary and the motor 5 maintains the rated operation. Therefore, at the time of the rated operation, the minimum power supply to replenish the slip component of the motor 5 is required. Yes, a certain amount of power supply is required.

The current measurement pattern 103 stored in the storage unit 101 in the control circuit 42 is copied and stored in the storage unit 101 as a duplicate current measurement pattern 104. If the motor 5 of the power supply system is continuously operated, the movable contact 34c (contact portion 34) in which the history of the rated operating current is periodically stored in the storage unit 101 in the control circuit 42 is stored. In addition to the program to be controlled, a program capable of evaluating the above-mentioned history information may be added.
Further, since the initial starting current and the time information of the starting period can be stored in the storage unit 101 of the control circuit 42, the motor that supplies power during the period until the motor 5 is replaced It is also possible to grasp changes in information over time.

Further, since the motor 5 is not replaced and the power supply system may be stopped by periodic inspection or the like, when the power is supplied to the motor 5 again, the starting current and the starting period already stored are stored. In this case, it is possible to confirm (process) the change history of the inductance component of the motor 5, and when this amount of change is large, the electric energy of the motor 5 is used. It is an important criterion for diagnosing deterioration of a machine that converts it into mechanical energy.
Regarding the apparent power supplied to the motor 5,
The amount of power determined by √3 x supply voltage x supply current can be used as a guide.

In the starting current period stored in the replication current measurement pattern 104 in the storage unit 101, if the starting current value stored in the replication current measurement pattern 104 is not exceeded during the starting current period, it is described in the drive program pattern 102. If a sequence in which the coil portion 35 is not excited is incorporated in the processing program of the storage unit 101, mistrip as a thermal relay at the time of starting the motor can be prevented.

Next, the control of the drive control unit 38 will be described.
The current sensor 36 measures the load current applied to the motor, converts the measured load current into an electric signal (current sensor signal 44s), and outputs the measured load current. The current sensor signal 44s output from the current sensor 36 is supplied to the signal line 44 and input to the control circuit 42 of the drive control unit 38 via the signal insulator 39 inserted in series with the signal line 44. .. The control circuit 42 determines whether or not the load current value based on the current sensor signal 44s output from the current sensor 36 and input via the signal insulator 39 exceeds a predetermined threshold value. Then, the control circuit 42 determines that “there is an abnormality” when the load current value exceeds the threshold value, and outputs the drive command signal 45s to the drive circuit (pulse generation circuit) 43 via the signal line 45. The drive circuit (pulse generation circuit) 43 that receives the drive command signal 45s from the control circuit 42 supplies drive power 46s to the coil portion 35 of the opening / closing portion 33 through the wiring 46 to excite the coil of the coil portion 35. When the coil of the coil portion 35 is excited, the movable contactor 34c separates from the pair of fixed contactors 34a and 34b and changes from the on state to the off state, the coil power supply line 26 is cut off, and the coil of the electromagnetic contactor 20 is cut off. The power supply to the unit 35 is stopped. Then, when the power supply to the coil portion 35 is stopped, the contact portion 24 of the magnetic contactor 20 is also changed from the on state to the off state, the main circuit electric wire 4 is cut off, and the load current applied to the motor 5 is cut off.

That is, when the load current value measured by the current sensor 36 exceeds a preset threshold value, the drive control unit 38 turns off the opening / closing unit 33 and cuts off the load current applied to the motor 5 by the magnetic contactor 20. ..
As described above, the overload protection relay 30 of the first embodiment electronically controls the operation of the opening / closing unit 33 when an overload is detected in the load current of the motor 5 to cut off the load current. Therefore, according to this first embodiment, the load current applied to the motor 5 is cut off with higher accuracy than in the case where the opening / closing part is operated by mechanical control by bimetal as in the conventional thermal relay. It is possible to provide an overload protection relay 30, an MCC unit 3 provided with the overload protection relay 30, and a power supply system 1.
Further, in the overload protection relay 30 of the first embodiment, the power supply system including the main circuit electric wire 4, the current sensor 36 and the contact 34 of the opening / closing unit 33 and the control system including the drive control unit 38 are signal insulators 39. And since it is insulated and separated by the coil portion 35 of the opening / closing portion 33, reliability can be improved.

Next, a case where the motor 5 is updated from a motor of efficiency classification IE1 (standard efficiency) or IE2 (high efficiency) to a motor of IE3 (premium efficiency) will be described.
Although there is no change in the supply current during rated operation, the inrush current value and starting current value of the current measurement pattern 103 clearly increase because the copper loss that constitutes the winding of the motor is kept low when the motor is started. To do.

In this case, in the excitation sequence of the coil unit 35 described above, the starting current value and the starting current period information of the power supply system are stored in the current value information detected in the current measurement pattern 103 and the duplicate current measurement pattern 104. Since the current value information is clearly different from the current value information, the procedure is to update the start current value and start current period information of the power supply system stored in the duplicate current measurement pattern 104, and further, the movable contact during this period. Mistrip of the motor 5 can be prevented by not transmitting the drive signal 46s by the drive program pattern 102 that opens 34c.
As a matter of course, it goes without saying that the above-mentioned apparent electric energy is updated.

After that, the motor may not be replaced and the power supply system may be stopped due to periodic inspections, etc., so if power is supplied to the motor again, the starting current and starting period that are updated and stored It can be compared and evaluated with the measurement result of. In this case, it is possible to confirm (process) the change history of the inductance amount and admittance component of the motor 5, and when this change amount is large, the deterioration of the machine that converts the electric energy of the motor 5 into mechanical energy. It is an important criterion for making a diagnosis.
If the starting current value stored in the replica current measurement pattern 104 is not exceeded during the start current period updated and stored in the duplicate current measurement pattern 104 of the storage unit 101, it is described in the drive program pattern 102. If a sequence in which the coil portion 35 is not excited is incorporated into the processing program of the storage unit 101, mistrip as the overload protecting relay 30 at the time of starting the motor can be prevented.

In addition, in FIG. 4, the control circuit 42 describes an example of a microprocessor having a storage unit 101 built-in, but the microprocessor can be provided with a serial communication interface. As shown in FIG. 2, the control circuit 12a of the wiring breaker 10 and the control circuit 22a of the electromagnetic contactor 20 in the MCC unit are configured by a microprocessor in the same manner as the control circuit 42 of the overload protection relay 30. If the microprocessor of the control circuit 12a and the microprocessor of the control circuit 22a are provided with a serial communication interface, the current information supplied to the motor on the power supply line is transmitted to each device in the MCC unit 3 (wiring breaker 10, electromagnetic contact). Information can be shared by the device 20 and the overload protection relay 30). In particular, the mistrip due to the excessive current of the wiring breaker 10 due to the starting current flowing through the motor 5 at the moment when the power supply to the motor 5 is started ( Accidental blocking) can be prevented.

The current pattern of the power supply system can be detected as an MCC unit 3 that integrates the wiring breaker 10, the electromagnetic contactor 20, and the overload protection relay 30, and after grasping the current start pattern of the motor 5, the current pattern of the motor 5 By comparing with the initial motor current pattern, it is possible to determine the abnormality of the motor 5.
The inrush current pattern, starting current pattern, and rated current pattern of the motor shown in FIG. 5 are detected and stored by the thermal relay as current value data, and the current value information stored in the wiring breaker of the first embodiment is electromagnetically contacted. By constructing a system shared between the device and the overload protection relay, unnecessary operation of the wiring breaker during the inrush current operation period shown in Fig. 5 can be prevented, and in addition, the thermal relay during the starting current period shown in the figure can be prevented. It is possible to prevent unnecessary operation of the overload protection relay 30 corresponding to the above.

Further, for example, by connecting the serial communication system in the MCC unit 3 to a system that monitors and monitors the deterioration of the motor 5 at the upper level and monitors and monitors the power consumed by the motor 5, the power consumption status of the motor 5 and the motor 5 It is possible to accurately share the alarm information from the deterioration diagnosis of the factory equipment, and to promote the predictive maintenance of factory equipment accurately.

(Second Embodiment)
The overload protection relay 30A according to the second embodiment of the present invention has substantially the same configuration as the overload protection relay 30 according to the first embodiment described above, and the following configurations are different.
That is, as shown in FIGS. 6 and 7, the overload protective relay 30A according to the second embodiment replaces the current sensor 36 and the signal insulator 39 of the first embodiment with a Rogovski coil type current sensor. It has 50. Other configurations are the same as in the first embodiment.

As shown in FIG. 6, the current sensor 50 has a bus bar 51 as a measurement conductor inserted in series with the internal power supply line LP2 and a logo as an air core coil installed around the bus bar 51. It has a ski coil (Rogowski Coil) 52 and. In this current sensor 50, an induced voltage is generated in the Rogovski coil 52 when the magnetic field due to the alternating current flowing in the bus bar 51 intersects with the Rogovski coil 52. Since this induced voltage becomes the time derivative value (di / dt) of the measured current, it becomes an output signal (current sensor signal 44s) proportional to the measured current by passing through the integrator. In this current sensor 50, the Rogowski coil 52 is arranged along the bus bar 51 through which the main circuit current flows, and the current can be measured by using the mutual inductance of the Rogowski coil 52. Therefore, the bus bar 51 and the Rogowski coil The insulation function between the 52 and the 52 can be ensured.

FIG. 7 shows current detection by the Rogovski coils 52 arranged in parallel with the bus bar 51. As shown in FIG. 7, in the current sensor 50, the current required for supplying electric power to the motor 5 is the change in the mutual inductance value between the Rogowski coil 52 and the bus bar 51 and the current value flowing through the bus bar 51 per unit time. It can be detected as a voltage in the form of the product of each frequency of rate and alternating current.

The current sensor 50 measures the load current applied to the motor 5 through the internal power supply line Lp2 and the bus bar 51 with the bus bar 51 and the Rogowski coil 52, converts the measured load current into an electric signal, and outputs the measured load current to the signal line 44. Then, the electric signal (current sensor signal 44s) transmitted from the current sensor 50 to the signal line 44 is transmitted to the control circuit 42 of the drive control unit 38. The alternate long and short dash line in FIG. 7 shows the insulation required between the control circuit system and the power supply system as a system. As an example, the insulation between the power supply system including the contact portion 34 of the opening / closing unit 33 and the bus bar 51 of the current sensor 50 and the control circuit system including the drive control unit 38 is shown.

The Rogowski coil 52 uses the alternating current flowing on the bus bar 51 side as a voltage represented by the following equation (1) by the mutual inductance M between the Rogowski coil 52 and the bus bar 51 and the angular frequency ω of the alternating current. V is detected.

Here, di / dt indicates the time change rate of the current i flowing through the bus bar 51. The current value can be calculated by integrating the above equation (1) with respect to time. That is, the current sensor 50 measures the load current value applied to the motor 5, converts the current value into a voltage signal (current sensor signal 44s), and outputs the current value to the signal line 44. Then, the voltage signal output from the current sensor 50 is sent to the control circuit 42 via the signal line 44. The control circuit 42 is shown as an example having a function having an analog / digital conversion.

In the MPU with a built-in ADC, the ADC is operated with a sampling time of a fixed cycle, and the current sensor signal 44s obtained by the Rogovski coil 52 measured by the above equation (1) is sampled and measured. Adding the measured voltage value V to the sampled voltage value V for each sampling time is an integration process in digital sampling, and this integration process can be expressed by the following equation (2).

For example, when measuring a current at a commercial frequency, the voltage value V _n to be sampled and measured by the above equation (2) at a sampling frequency of 20 KHz is added in 1 millisecond, and then the voltage measured in 1 millisecond. the value V _{n + 1,} by repeating the adding ..., current I _n, I _n + ₁ at each measurement interval using the above equation _(2), it is possible to digitally calculates .......

Regarding the mutual inductance M and commercial AC frequency ω of the Rogovski coil 52 described in the above equations (1) and (2), the results obtained under certain conditions in the pre-shipment inspection of the product are built into the MPU. If the information is stored in the stored memory, the correction can be made based on the stored data.

The voltage signal detected by the current sensor 50 is a current measurement pattern 103 stored in the storage unit 101 in the control circuit 42 to magnetically excite the motor 5 after the power supply system to the motor 5 is supplied. The start current is supplied to the inductor component that generates the admittance component and motor torque and is involved in driving.
When the motor 5 reaches the rated operation, the rotational acceleration is no longer necessary and the motor 5 maintains the rated operation. Therefore, at the time of the rated operation, the minimum power supply to replenish the slip component of the motor 5 is required. Yes, a certain amount of power supply is required.

The current sensor 50 measures the load current applied to the motor, converts the measured load current into an electric signal (current sensor signal 44s), and outputs the measured load current. The current sensor signal 44s output from the current sensor 50 is input to the control circuit 42 of the drive control unit 38. The control circuit 42 determines whether or not the load current value based on the current sensor signal 44s output from the current sensor 50 exceeds a predetermined threshold value. Then, the control circuit 42 determines that “there is an abnormality” when the load current value exceeds the threshold value, and outputs the drive command signal 45s to the drive circuit (pulse generation circuit) 43 via the signal line 45. The drive circuit (pulse generation circuit) 43 that receives the drive command signal 45s from the control circuit 42 supplies the drive power 46s to the coil portion 35 of the opening / closing portion 33 to excite the coil of the coil portion 35. When the coil of the coil portion 35 is excited, the movable contactor 34c separates from the pair of fixed contactors 34a and 34b and changes from the on state to the off state, the coil power supply line 26 is cut off, and the coil of the electromagnetic contactor 20 is cut off. The power supply to the unit 35 is stopped. Then, when the power supply to the coil portion 35 is stopped, the contact portion 34 of the magnetic contactor 20 is also changed from the on state to the off state, and the main circuit electric wire 4 is cut off to cut off the load current applied to the motor 5.
That is, when the load current value measured by the current sensor 50 exceeds a preset threshold value, the drive control unit 38 turns off the opening / closing unit 33 and cuts off the load current applied to the motor 5 by the magnetic contactor 20. ..

As described above, the overload protection relay 30A according to the second embodiment opens and closes when an overload is detected in the load current of the motor 5, similarly to the overload protection relay 30 according to the first embodiment described above. The operation of the unit 33 is electronically controlled to cut off the load current. Therefore, also in this second embodiment, the load current applied to the motor 5 is cut off with higher accuracy than in the case where the opening / closing part is operated by mechanical control by bimetal as in the conventional thermal relay. It is possible to provide an overload protection relay 30A capable of the above, an MCC unit 3 provided with the overload protection relay 30A, and a power supply system 1.
Further, the overload protection relay 30A of the second embodiment includes a power supply system including a main circuit wire 4, a bus bar 51 of a current sensor 50, and a contact portion 34 of an opening / closing portion 33, and a control system including a current drive control unit 38. However, since it is insulated and separated by the Rogowski coil 52 of the current sensor 50 and the coil portion 35 of the opening / closing portion 33, reliability can be improved.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations.

1 ... Power supply system 2 ... Power supply source 3 ... MCC unit 4 ... Main circuit wire (electric line)
5 ... Motor (electric motor)
10 ... Molded case circuit breaker 20 ... Electromagnetic contactor 21 ... Opening and closing part 24 ... Contact part 24a, 24b ... Fixed contactor 24c ... Movable contactor 25 ... Coil part 28 ... First external terminal 29 ... Second external terminal 30 ... Over Load protection relay 31 ... 1st external terminal 32 ... 2nd external terminal 33 ... Opening / closing part (switch)
34 ... Contact part (contactor)
34a, 34b ... Fixed contact (fixed contact)
34c ... Movable contactor (movable contact part)
35 ... Coil unit 36 ... Current sensor 37 ... Power generation unit 37A ... Rectifier circuit 37B ... Voltage detection circuit 37C ... Power supply circuit 38 ... Drive control unit 39 ... Signal insulator 40 ... Power supply 41 ... Switch 42 ... Control circuit 43 ... Drive circuit 44, 45 ... Signal line 46 ... Wiring 50 ... Current sensor 51 ... Bus bar (measurement conductor)
52 ... Rogovski coil (air core coil)
101 ... Storage unit 102 ... Drive program pattern 103 ... Current measurement pattern 104 ... Duplicate current measurement pattern Lp1, Lp2 ... Internal power supply line

Claims (8)

A current sensor that measures the load current applied to the electric motor through the electric circuit, converts the measured load current into an electric signal, and outputs it.
A drive that inputs an electric signal output from the current sensor and drives an electromagnetic contactor to cut off the load current applied to the electric motor when the load current value based on the input electric signal exceeds a predetermined threshold value. Control unit and
An overload protective relay characterized by being equipped with. It is characterized in that it is further provided with a signal insulator that is inserted in series with a signal line that transmits an electric signal of the current sensor to the drive control unit and that secures insulation between the current sensor and the drive control unit. The overload protection relay according to claim 1. The magnetic contactor includes a contact portion that is inserted into the electric circuit in series, and a coil portion that opens and closes the contact portion.
The overload according to claim 2, wherein the drive control unit is insulated and separated from the power supply system including the electric circuit, the current sensor, and the contact portion by the signal insulator and the coil portion. Protective relay. The overload protecting relay according to claim 1, wherein the current sensor is a Rogowski coil type current sensor having a measuring conductor and an air core coil arranged around the measuring conductor. The magnetic contactor includes a contact portion that is inserted into the electric circuit in series, and a coil portion that opens and closes the contact portion.
The drive control unit is characterized in that it is insulated and separated from the electric circuit and the power supply system including the measuring conductor and the contact portion of the current sensor by the air core coil and the coil portion of the current sensor. The overload protection relay according to claim 4. The drive control unit processes a converter that converts the starting current value and the rated current value of the electric motor measured by the current sensor into digital values, and the digital value data converted by the converter for each starting current value. The overload according to any one of claims 1 to 5, wherein the processing device is provided, and a storage unit for storing the starting current value and the rated current value processed by the processing device is provided. Protective relay. The overload protection relay according to any one of claims 1 to 6.
A molded case circuit breaker that opens and closes the electric circuit, the electromagnetic contactor, and
An MCC unit characterized by being equipped with. The overload protection relay according to claim 6 and
An opening / closing unit for opening / closing the electric circuit, and a molded case circuit breaker and an electromagnetic contactor having a drive control unit for controlling the opening / closing of the opening / closing unit are provided.
The drive control unit of each of the molded case circuit breaker and the magnetic contactor includes a digital processing device having digital processing and communication functions.
Further, it is characterized by including a transmission system that transmits data stored in the storage unit of the overload protection relay to the drive control unit of each of the molded case circuit breaker and the electromagnetic contactor by serial communication. MCC unit to do.

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