JP7567679B2 - Coil temperature sensor fault detection system and coil temperature sensor fault detection method - Google Patents

Description

The present invention relates to a technology for detecting faults in coil temperature sensors of motors such as vehicle-mounted motors.

In an inverter that drives a three-phase motor, there is prior art in which a temperature sensor is provided in the motor coil to protect the coil from overheating (for example, Patent Document 1).

In addition, in order to detect failures in the temperature sensor in the temperature detection section of the motor coil, there is a technology that monitors the health of the sensor and detects failures by comparing the detection values of two temperature sensors attached to two phases of the three-phase coil.

In the inverter 3 shown in FIG. 3, the main circuit unit 4 supplies power to the motor 2. The conventional temperature sensor abnormality determination unit 5 detects the U-phase coil temperature Tu and the V-phase coil temperature Tv from the coil temperature sensor 6 provided in the U-phase coil and the V-phase coil in the motor 2. The conventional coil temperature sensor failure detection circuit 20 of the temperature sensor abnormality determination unit 5 shown in FIG. 4 calculates the difference between the motor coil temperature detection value 1 (Tu) and the motor coil temperature detection value 2 (Tv) by the first subtraction circuit 11. The difference is provided to the second subtraction circuit 16 as an absolute value via the absolute value circuit 12. Then, when the absolute value exceeds the subtraction circuit threshold in the second subtraction circuit 16, it is determined that one of the two temperature sensors has failed. This technology is based on the premise that approximately equal currents flow through each phase of the three-phase motor and the coil temperatures of each phase are approximately equal.

Japanese Patent Application Publication No. 10-62266 JP 2013-5475 A

However, when the motor is locked, the currents flowing through the motor's three-phase coils become unbalanced. This causes a discrepancy in the coil temperatures of each phase, resulting in a false detection of a temperature sensor abnormality even if two temperature sensors are normal. In addition, even after the motor is unlocked, the thermal time constant of the coil temperature is long, so the above-mentioned false detection of a temperature sensor abnormality occurs during the period from when the motor is unlocked until a certain amount of time has passed.

In consideration of the above circumstances, the present invention aims to detect temperature sensor faults frequently and with high accuracy by enabling fault diagnosis of the coil temperature sensor while the motor is running, including when the motor is locked.

Therefore, one aspect of the present invention is a coil temperature sensor fault detection system for a three-phase motor, which includes a temperature sensor anomaly determination unit that performs an anomaly determination for the coil temperature sensor based on a value obtained by subtracting the temperature correction value of the coil temperature sensor at the time of locking from the absolute value of the difference between the motor coil temperature detection values of different phases of the three phases detected by the coil temperature sensor when the motor is locked.

In one aspect of the present invention, in the coil temperature sensor fault detection system, after the motor is unlocked, the temperature sensor abnormality determination unit determines an abnormality of the coil temperature sensor based on a value obtained by subtracting a temperature correction value H2 of the coil temperature sensor, as shown in the following equation (1), from the absolute value of the difference between the motor coil temperature detection values of different phases of three phases detected by the coil temperature sensor.
H2=H1×exp(-t/τ)…(1)
H1: Motor coil temperature correction value when the motor is locked t: Elapsed time (seconds) after the motor is unlocked
τ: motor coil temperature thermal time constant of the motor In one aspect of the present invention, in the coil temperature sensor failure detection system, the motor is driven by an inverter.

One aspect of the present invention is a method for detecting a coil temperature sensor failure in a three-phase motor, in which, when the motor is locked, an abnormality in the coil temperature sensor is determined based on a value obtained by subtracting a temperature correction value of the coil temperature sensor at the time of locking from the absolute value of the difference between motor coil temperature detection values of different phases of the three phases detected by the coil temperature sensor.

According to the present invention, it is possible to diagnose faults in the coil temperature sensor while the motor is running, including when the motor is locked, thereby enabling temperature sensor fault detection to be performed frequently and with high accuracy.

1 is a block diagram of a coil temperature sensor fault detection system according to an embodiment of the present invention; A coil temperature sensor fault detection circuit of the coil temperature sensor fault detection system. FIG. 1 is a block diagram of a conventional coil temperature sensor fault detection system. Conventional coil temperature sensor fault detection circuit.

The following describes an embodiment of the present invention with reference to the drawings.

The coil temperature sensor fault detection system 1, which is one embodiment of the present invention shown in Figure 1, includes a three-phase motor 2 and an inverter 3.

The inverter 3 includes a main circuit section 4 and a temperature sensor abnormality determination section 5.

The main circuit section 4 drives and controls the motor 2. The motor 2 is equipped with a coil temperature sensor 6, a rotation speed sensor 7, and a torque sensor 8.

The temperature sensor abnormality determination unit 5 performs an abnormality determination for the temperature sensor based on the absolute value of the difference between the coil temperature detection values Tu and Tv at two points (U, V) when the motor 2 is locked, minus the temperature correction value of the temperature sensor when the motor 2 is locked or after the motor is unlocked.

The motor 2 coil temperature detection values Tu, Tv, as well as the motor 2 rotation speed detection value and torque detection value are input to the temperature sensor anomaly determination unit 5. These rotation speed detection value and torque detection value may be used for the original control of the inverter 3. In this case, there is no need to provide a new separate rotation speed sensor 7 and torque sensor 8. The motor torque detection value may also be replaced with a torque command value that is input from outside and used for controlling the inverter 3. In this case, there is also no need to provide a separate torque sensor 8.

The temperature sensor abnormality determination unit 5 specifically implements the coil temperature sensor fault detection circuit 10 illustrated in FIG. 2.

The coil temperature sensor failure detection circuit 10 determines whether the coil temperature sensor is faulty when the motor 2 is locked and when it is in normal operation.

The coil temperature sensor fault detection circuit 10 includes a first subtraction circuit 11, an absolute value circuit 12, a motor lock determination circuit 13, a switch circuit 14, a first-order lag filter 15, a second subtraction circuit 16, and a third subtraction circuit 17.

The first subtraction circuit 11 outputs the difference between the motor coil temperature detection value 1 (coil temperature detection value Tu) and the motor coil temperature detection value 2 (coil temperature detection value Tv) input from the coil temperature sensor 6.

The absolute value circuit 12 outputs the absolute value of the difference input from the first subtraction circuit 11.

The motor lock determination circuit 13 determines whether the motor 2 is locked or unlocked based on the rotation speed detection value and torque detection value of the motor 2 input from the rotation speed sensor 7 and torque sensor 8, respectively, and outputs a signal indicating the determined state. For example, the motor lock determination technology described in Patent Document 2 is used for this determination.

Based on a signal input from the motor lock determination circuit 13, the switch circuit 14 selects and outputs either a temperature correction value H1 at the time of lock or a temperature correction value H2 after unlocking via a first-order lag filter 15 based on the following initial value, target value and filter time constant.
Initial value: Motor coil temperature correction value when motor 2 is locked (H1)
Target value: 0
Filter time constant: Motor coil temperature thermal time constant (τ)
The temperature correction value H1 during locking is set based on the results of a pre-test that actually measures the coil temperature of each phase during locking of the motor 2. The coil temperature thermal time constant (τ) is set to a value in the data sheet of the motor 2 or a measured time constant obtained by a pre-test.

The temperature correction value H2 via the first-order lag filter 15 after the lock is released is calculated by the following formula (1).
H2=H1×exp(-t/τ)…(1)
H1: Motor coil temperature correction value when the motor 2 is locked t: Time (seconds) elapsed after the motor 2 is unlocked
τ: motor coil temperature thermal time constant of motor 2. A second subtraction circuit 16 outputs a value obtained by subtracting the temperature correction value H1 at the time of locking or the temperature correction value H2 after unlocking from the switch circuit 14 from the absolute value from the absolute value circuit 12.

The third subtraction circuit 17 outputs the value obtained by subtracting the fault recognition threshold from the value output from the second subtraction circuit 16.

Then, the temperature sensor abnormality determination unit 5 determines whether the temperature sensor is abnormal based on the value obtained by subtraction by the third subtraction circuit 17.

According to the coil temperature sensor fault detection circuit 10 described above, when the motor 2 is locked, the switch circuit 14 outputs the temperature deviation between the coil temperature sensors 6 when locked to the second subtraction circuit 16 as the temperature correction value H1 when locked. The second subtraction circuit 16 prevents erroneous detection by subtracting the temperature correction value H1 from the temperature detection value difference (absolute value) from the absolute value circuit 12.

On the other hand, when the motor 2 is unlocked, the temperature correction value H1 is supplied to the first-order lag filter 15, and the obtained temperature correction value H2 is output to the second subtraction circuit 16. The second subtraction circuit 16 subtracts the temperature correction value H2 from the temperature detection value difference (absolute value) from the absolute value circuit 12, thereby preventing erroneous detection while maintaining a certain level of accuracy.

Therefore, according to the coil temperature sensor fault detection system 1 described above, when the motor 2 is locked, fault detection is performed using a value after temperature correction that takes into account the temperature difference between the two coil temperature sensors 6 due to locking. Therefore, if the temperature correction value is appropriate, false detection of an abnormality in the coil temperature sensor can be avoided.

In addition, after the motor 2 is unlocked, the temperature correction value is reduced by the first-order lag filter 15 based on the thermal time constant, so there is no need to perform diagnosis with an excessively large threshold value (or a temperature difference that is corrected more than necessary). Furthermore, since correction is performed according to the thermal time constant of the coil temperature, the possibility of erroneous detection is reduced if the temperature correction value and time constant settings are appropriate.

As a result, the fault detection accuracy and diagnostic frequency of the coil temperature sensor of the motor 2 are improved. Furthermore, the coil temperature sensor fault detection circuit of the present invention can be effectively applied to systems that drive three-phase motors without being limited to inverters.

1...Coil temperature sensor failure detection system 10...Coil temperature sensor failure detection circuit, 11...First subtraction circuit, 12...Absolute value circuit, 13...Motor lock determination circuit, 14...Switch circuit, 15...First-order lag filter, 16...Second subtraction circuit, 17...Third subtraction circuit 2...Motor 3...Inverter 4...Main circuit section 5...Temperature sensor abnormality determination section 6...Coil temperature sensor 7...Rotation speed sensor 8...Torque sensor

Claims (4)

A coil temperature sensor fault detection system for a three-phase motor, comprising:
A coil temperature sensor failure detection system characterized by comprising a temperature sensor abnormality determination unit that determines whether the coil temperature sensor is abnormal based on a value obtained by subtracting the temperature correction value of the coil temperature sensor at the time of locking from the absolute value of the difference between the motor coil temperature detection values of three different phases detected by the coil temperature sensor when the motor is locked. The coil temperature sensor failure detection system described in claim 1, characterized in that after the motor is unlocked, the temperature sensor abnormality determination unit determines whether the coil temperature sensor is abnormal based on a value obtained by subtracting a temperature correction value H2 of the coil temperature sensor, as shown in the following equation (1), from the absolute value of the difference between the motor coil temperature detection values of different phases of the three phases detected by the coil temperature sensor.
H2=H1×exp(-t/τ)…(1)
H1: Motor coil temperature correction value when the motor is locked t: Elapsed time (seconds) after the motor is unlocked
τ: motor coil temperature thermal time constant of the motor The coil temperature sensor fault detection system according to claim 1 or 2, characterized in that the motor is driven by an inverter. A method for detecting a fault in a coil temperature sensor of a three-phase motor, comprising:
A coil temperature sensor failure detection method characterized in that, when the motor is locked, an abnormality of the coil temperature sensor is determined based on a value obtained by subtracting a temperature correction value of the coil temperature sensor at the time of locking from the absolute value of the difference between the motor coil temperature detection values of three different phases detected by the coil temperature sensor.

Images