JPH08275598A - Controller for induction motor - Google Patents

Abstract

PURPOSE: To perform R2 compensation control and thermal protection control of an induction motor using a temperature sensor. CONSTITUTION: While detecting the temperature Tmp of the winding of an induction motor 1 through a temperature sensor 2, a control circuit 6 performs R2 compensation control and vector control of the induction motor 1 thus feeding AC power thereto. When a temperature detection signal Tmp increases to exceeds a first temperature T1, a first decision means 7 delivers a first protective signal DET1 and when a second temperature T2 is exceeded, a second decision means 9 delivers a second protective signal DET2. When the temperature sensor 2 is disconnected, a disconnection detecting means 11 delivers a disconnection signal DET3. The control circuit 6 stops the operation based on the second protective signal DET2, deduces the AC power based on the first protective signal DET1 and presents an alarm when the disconnection signal DET3 is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor control device, and more particularly to an induction motor control device having a heat protection function for the induction motor.

[0002]

2. Description of the Related Art As an induction motor control device using vector control, there is a control device which performs R2 compensation control and heat protection control of the induction motor. FIG. 4 shows the configuration of the main part of a conventional device of this type. In FIG. 4, the temperature sensor 2 and the crixon 3 are attached to the winding of the induction motor 1, and the output signals of the temperature sensor 2 and the crixon 3 are taken into the control device through the interfaces 4 and 5, and the vector control is performed by the output signal of the temperature sensor 2. R2 compensation control is performed when
The thermal protection control of the induction motor 1 is performed by the output signal of the crixon 3.

The temperature sensor 2 outputs an analog signal proportional to the temperature, and the crixon 3 outputs a sequence signal for opening or closing when the temperature exceeds a predetermined temperature for thermal protection control.

Further, since the control portion of vector control, R2 compensation control, and thermal protection control is not directly related to the present invention, a publicly known technique (for example, Denki Shoin "New Drive Electronics" p. 209) can be used, so here. The description is omitted.

[0005]

Generally, an induction motor having a large capacity for vector control is equipped with a temperature sensor for performing R2 compensation control. However, a temperature sensor for controlling thermal protection of the induction motor ( There was a problem that it had to be attached separately (Crickson etc.). or,
When the temperature sensor is broken or otherwise malfunctions, the functions of R2 compensation control and thermal protection control are lost.

The present invention has been made in order to solve the above problems, and an object of the present invention is to perform R2 compensation control of an induction motor using a temperature sensor and thermal protection control. An object of the present invention is to provide a control device for an induction motor that can continue operation even if some of the temperature sensors fail using a plurality of temperature sensors.

[0007]

In order to achieve the above object, the present invention provides a temperature sensor for outputting a temperature detection signal according to the temperature of a winding of an induction motor, and the induction motor based on the temperature detection signal. Is provided with control means for performing vector control while performing R2 compensation control to supply AC power to the induction motor, and the control means causes the temperature detection signal to cause the temperature of the winding to exceed a first temperature. When the first
And a second determining means for outputting a second protective signal when the temperature of the winding exceeds a second temperature. Further, the control means is provided with a disconnection detecting means for determining a disconnection and outputting a disconnection signal when the resistance value of the temperature sensor exceeds a predetermined resistance value.

Further, the temperature sensor has a plurality of temperature sensors connected in parallel and outputs a single temperature detection signal, and the control means is responsive to the resistance values of the plurality of temperature sensors connected in parallel. Depending on the number of temperature sensors determined by the disconnection detection means, the disconnection detection means outputs a disconnection signal when determining the number of temperature sensors connected in parallel and determining that at least one temperature sensor is disconnected. Temperature detection signal correction means for correcting the temperature detection signal by the
The R2 compensation control is performed and the first protection signal and the second protection signal are detected. Further, the control means stops the operation by the second protection signal. Further, the control means reduces the AC power by the first protection signal. Further, when the disconnection signal is detected, the control means continues the operation of the induction motor with the corrected temperature detection signal while displaying an alarm.

[0009]

The control means drives the induction motor by performing vector control while performing R2 compensation control by the temperature detection signal output from the temperature sensor. When the temperature of the winding of the induction motor exceeds the first temperature, the first judging means outputs the first protection signal, and when it exceeds the second temperature, the second judging means outputs the second protection signal. To be done. Further, when the resistance value of the temperature sensor exceeds a predetermined resistance value, a disconnection signal is output from the disconnection detection means. Further, when at least one of the temperature sensors connected in parallel is disconnected, the disconnection detection means determines the number of sound temperature sensors from the change in the combined resistance value and outputs a disconnection signal. Then, the temperature detection signal correction means outputs the temperature detection signal corrected according to the number of sound temperature sensors. Then, based on the corrected temperature detection signal, R2 compensation control is performed and the first protection signal and the second protection signal are detected. Further, the control means stops the operation by the second protection signal, reduces the AC power by the first protection signal, and when a disconnection signal is detected, the temperature is corrected while displaying an alarm. The operation of the induction motor is continued by the detection signal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment corresponding to claims 1, 2, 4, and 5 of the present invention. In FIG. 1, 1 is an induction motor, 2
Is a temperature sensor attached to the winding of the induction motor 1,
Reference numeral 4 is an interface for taking the output signal of the temperature sensor 2 into the control device, 6 is a control circuit for performing vector control while performing R2 compensation control to supply AC power to the induction motor 1, 7 and 9 are comparators, 8 And 10 are setting devices, 11
Is a disconnection detector that detects disconnection from the resistance value of the temperature sensor.

In the above structure, the control circuit 6 performs vector control while performing R2 compensation control by the temperature detection signal Tmp of the winding of the induction motor 1 detected via the temperature sensor 2 and the interface 4. Supply AC power to.

When the temperature of the winding of the induction motor 1 rises, the output voltage of the temperature sensor 2 rises, and as shown in FIG.
The temperature detection signal Tmp increases in proportion to the temperature of the winding. When the temperature detection signal Tmp exceeds the set value T1 of the setter 8, the comparator 7 outputs the first protection signal DET1.
The set value T1 is the allowable limit temperature Tmax of the winding of the induction motor 1.
It is set to a slightly lower value Trun, and the first protection signal DE
The alarm is displayed by T1, and the control circuit 6 carries out an operation of suppressing or reducing the AC output power (for example, control such as speed reduction). (Claim 5) Furthermore, when the temperature of the winding of the induction motor 1 rises and the temperature detection signal Tmp increases and exceeds the set value T2 of the setter 10,
The comparator 9 outputs the second protection signal DET2. The set value T2 is set to the allowable limit temperature Tmax of the winding of the induction motor 1, and the control circuit 6 is stopped by the second protection signal DET2. (Claim 4) Further, when the temperature sensor 2 is disconnected, the resistance value rapidly increases, so the disconnection detector 11 detects this and outputs a disconnection signal DET3. In this case, unlike normal temperature rise, the resistance value approaches infinity in a short time.Therefore, disconnection is detected by detecting the rate of change or detecting that the resistance value itself becomes a level that is impossible with temperature rise. Identify.

By this disconnection signal EDT3, an alarm display different from a normal alarm can be displayed. (Claim 2) FIG. 3 shows an embodiment corresponding to claims 3 and 6 of the present invention.

In FIG. 3, reference numeral 2 is a plurality of temperature sensors attached to the windings of the induction motor 1, all of which are connected in parallel and output as one temperature detection signal. Reference numeral 12 outputs a signal Sn for determining the number of temperature sensors connected in parallel according to the resistance values of a plurality of temperature sensors connected in parallel, and a disconnection signal when it is determined that at least one temperature sensor is disconnected. Disconnection detector that outputs DET3, 13
Is a temperature detection signal correction unit that determines the number of sound temperature sensors based on the signal Sn and corrects the temperature detection signal Tmp according to the number of temperature sensors. This corrected temperature detection signal Tmp is given as the temperature detection signal Tmp in FIG.

In the above structure, when a wire breakage occurs in an arbitrary number of temperature sensors among the plurality of temperature sensors, the resistance value changes corresponding to the number of wire breakage temperature sensors. The disconnection detector 12 determines the disconnection of the temperature sensor from the change in the resistance value and outputs a disconnection signal DET3 and also outputs a signal Sn indicating the number of sound temperature sensors. This signal S
The temperature detection signal correction unit 13 corrects the output signal Tmp ′ from the sound temperature sensor by n, and outputs the same temperature detection signal Tmp as the original.

By the corrected temperature detection signal Tmp, R
2 Compensation control is performed and the first protection signal and the second protection signal are detected. Therefore, according to this embodiment, when a disconnection occurs in some of the temperature sensors, it is possible to continue the operation of the induction motor with the corrected temperature detection signal while displaying the alarm.

[0017]

According to the invention, thermal protection control is performed using a temperature sensor for R2 compensation control without using a temperature sensor such as crixon for thermal protection control, and a plurality of temperature sensors are used. By using this, it is possible to provide an induction motor control device capable of maintaining the functions of the R2 compensation control and the thermal protection control and continuing the operation even if some of the temperature sensors fail.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment corresponding to claims 1, 2, 4, and 5 of the present invention.

FIG. 2 is a characteristic diagram of a temperature detection signal Tmp of FIG.

FIG. 3 is a configuration diagram of an embodiment corresponding to claims 3 and 6 of the present invention.

FIG. 4 is a configuration diagram of a main part of a conventional device.

[Explanation of symbols]

1 ... Induction motor 2 ... Temperature sensor 3 ... Crickson 4, 5 ... Interface 6 ... Control circuit 7, 9 ... Comparator 8, 10 ... Setting device 11 ... Disconnection detector 12 ... Disconnection detector (number of disconnection) 13 ... Temperature detection Signal correction unit

Claims (6)

[Claims] 1. A temperature sensor that outputs a temperature detection signal according to the temperature of a winding of an induction motor, and vector control is performed on the induction motor by performing R2 compensation control of the induction motor by the temperature detection signal. A first determination means for outputting a first protection signal when the temperature of the winding exceeds a first temperature in response to the temperature detection signal; A control device for an induction motor, comprising: a second determination unit that outputs a second protection signal when the temperature of the winding exceeds a second temperature. 2. The induction motor control device according to claim 1, further comprising a disconnection detecting means for determining a disconnection and outputting a disconnection signal when the resistance value of the temperature sensor exceeds a predetermined resistance value. An induction motor control device characterized by the above. 3. The control device for an induction motor according to claim 1, wherein the temperature sensor has a plurality of temperature sensors connected in parallel and outputs a single temperature detection signal, and the control means includes the parallel sensor. A disconnection detecting unit that outputs a disconnection signal when determining the number of temperature sensors connected in parallel according to the resistance values of the plurality of connected temperature sensors and determining that at least one or more temperature sensors are disconnected.
A temperature detection signal correction means for correcting the temperature detection signal according to the number of temperature sensors determined by the disconnection detection means, and performing the R2 compensation control and the first protection signal by the corrected temperature detection signal. And a second protection signal is detected, an induction motor control device. 4. The control device for an induction motor according to claim 1, wherein the control means stops the operation in response to the second protection signal. apparatus. 5. The induction motor control device according to claim 1, wherein the control means reduces the AC power by the first protection signal. Control device. 6. The control device for an induction motor according to claim 3, wherein the control means, when a disconnection signal is detected,
A control device for an induction motor, which continues the operation of the induction motor by a corrected temperature detection signal while displaying an alarm.