JP2002101668A - Life time estimation method of semiconductor power converter and semiconductor power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that it takes labor and time to estimate the life time of a semiconductor power converter and life time prediction based on the number of the time of switching of an element, but life time prediction becomes rough when based on the junction temperature. SOLUTION: A temperature detector 10 measures the base plate temperature of IGBT of an inverter 2, a ripple temperature detector 13 measures the ripple temperature from the base plate temperature detection value in the unit measuring period of operation/stop by a temperature range, a counter 14 counts the number of the times of generation for each ripple temperature every unit measuring period, a power damage rate calculation part 15 finds an accumulated damage rate CD from the number of the times of the life time by temperature range for the ripple temperature and the number of the times of practical generation, and a life time calculation part 16 estimates the life time L(=1/CD) from an accumulated damage rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor power conversion device and a method for estimating the life of a power device used as a main circuit element of the device.

[0002]

2. Description of the Related Art There are not many devices for online estimation of the remaining life of a main circuit element used in a power converter. For example, the product life of a general-purpose inverter is generally about 10 years, and the life of a single main circuit element such as an IGBT rarely affects the life of the entire product.

[0003] However, in equipment for applications requiring a product life of more than 20 years, maintenance and replacement of main circuit elements will be required. The problem in this case is the replacement time.
That is, the estimation of the remaining life is indispensable.

In the conventional life survey, a sample of a part of a main circuit element is sampled, an unsealing inspection is performed, and judgment is made based on observation results such as solder deterioration.

Further, a method of predicting the life of an inverter element based on the number of switching times of the inverter element (Japanese Patent Laid-Open No. Hei 8-2754)
86, a method of monitoring the state of each part of the inverter and estimating the life of the entire inverter (Japanese Patent Laid-Open No. 6-705).
No. 33), a method of estimating the junction temperature of a semiconductor switching element and determining the life thereof (Japanese Patent Laid-Open No. Hei 3-26)
1877), a method of estimating the life from the relationship between the junction temperature and the power cycle (Japanese Patent Laid-Open No. 8-5176)
No. 8) has been proposed.

[0006]

The conventional method based on sample extraction cannot be applied to a system in which the apparatus is operated continuously, and requires a lot of trouble to diagnose the life.

On the other hand, the life prediction based on the number of switching times of the elements and the junction temperature can be performed in the operation state of the apparatus, but does not consider the operation conditions of the apparatus, and is only a rough life prediction method.

An object of the present invention is to provide a semiconductor power conversion device and a method for estimating the life of a power device, which are capable of diagnosing the life in the operating state of the device and improving the prediction accuracy.

[0009]

Means for Solving the Problems IGBT is a typical main circuit element of a semiconductor power converter, and it has been revealed by manufacturers that the main factor of the life is thermal deterioration of a solder portion. . The internal temperature of the IGBT module repeatedly rises or falls in accordance with the supplied current. In particular, when the operation of the apparatus is frequently stopped or when the load changes suddenly, thermal stress due to temperature ripple occurs in the solder portion of the IGBT chip. The cause is due to the difference in thermal expansion coefficient between the ceramic board mounted on the chip and the copper base board. Due to the repetition of the thermal stress, cracks occur in the solder between the ceramic plate and the base plate. This crack increases the thermal resistance of the IGBT chip, and eventually the IGBT is destroyed by overheating of the chip.

Therefore, the present invention has a function of estimating the remaining life of a main circuit element such as an IGBT in order to prevent the deterioration of the life of the main circuit element, and clarifies the replacement time.

The thermal degradation inside the IGBT occurs structurally at two locations. The life of each factor is as follows, and is indicated as the number of times of the ripple temperature.

Power cycle life: The thermal fatigue life of the solder portion of the aluminum bonding wire on the IGBT chip.

Thermal fatigue life: Thermal fatigue life of the solder portion between the copper base plate and the ceramic plate for mounting the IGBT chip.

Generally, the thermal fatigue life of the two types is shorter. Therefore, the present invention provides an IG based on thermal fatigue life.
Estimate BT life.

As described above, the present invention is characterized by the following method and apparatus.

(Invention of Method) A method for estimating the life of a semiconductor power converter using a power device as a main circuit element, wherein the base plate temperature of the main circuit element is directly measured or estimated from the cooling fin temperature of the main circuit element. Then, the ripple temperature of the base plate temperature in the unit measurement period is measured for each temperature range, the number of occurrences for each of the ripple temperatures is counted for each unit measurement period, and the number of lifetimes N1, for the ripple temperature, for each temperature range. .., And the actual number of occurrences n1, n2, n3,..., And the life L is estimated according to the following equation: CD = (n1 / N1 + n2 / N2 + n3 / N3 +.

(Invention of Apparatus) A semiconductor power conversion apparatus using a power device as a main circuit element, wherein temperature detecting means for directly measuring the base plate temperature of the main circuit element or estimating from the cooling fin temperature of the main circuit element. A ripple temperature detecting unit that measures the ripple temperature from the base plate temperature detected value in a unit measurement period for each temperature range, a counter unit that counts the number of occurrences for each of the ripple temperatures in the unit measurement period, From the life times N1, N2, N3,... For each temperature range with respect to the ripple temperature and the actual occurrence times n1, n2, n3,. Means for estimating L.

Further, the unit measurement period may be a period from the start of operation of the semiconductor power conversion device to the start of the next operation, or a period from the time when the measured temperature starts to rise until the temperature starts to rise next. Features.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a configuration diagram of an inverter according to an embodiment of the present invention. The apparatus main body drives the electric motor 3 serving as a load by converting the DC power into DC power by the rectifier 1 and converting the DC power into AC power whose voltage and frequency are controlled by an inverter 2 having an IGBT as a main circuit element. Further, the control device 4 of the inverter 2 generates a gate control signal based on a start / stop command and a speed command by a program setting or the like, and powers the gate control signal by the driver 5 to become a main circuit element of the inverter 2. By controlling the gate of the IGBT, the speed of the electric motor 3 is controlled according to the speed command.

Various methods are used for controlling the inverter. For example, a speed control method of VVVF or CVCF, a control system using a vector control method, a torque control instead of the speed control, an ON / OFF control of the IGBT are used. PWM off control
Various combinations are made such as a control method, a power transistor instead of an IGBT as a power device, and a GTO. As the semiconductor power converter, there are a converter and a chopper instead of an inverter, and there is a system in which the control device has a hardware configuration or a system in which a microprocessor has a software configuration.

In this embodiment, a case is shown in which the control device 4 has a software configuration using a microprocessor, and a life estimation device for a power device is provided using its information processing function.

The life estimation apparatus includes a temperature detector 10 for measuring the temperature by attaching a thermistor to a case (copper base plate) of the IGBT module of the inverter 2 as hardware, and a temperature detector 10 for detecting the temperature. An A / D converter 11 for converting a signal into digital value temperature data is provided. The thermistor is one of the IGBTs.
And the other IGBTs are considered the same.

As the software configuration of the life estimation device, processing elements 12 to 16 are provided. The time measurement unit 12 extracts an operation pattern PT having time information of the operation time and the stop period from the operation / stop command of the inverter.

The ripple temperature detecting section 13 includes the time measuring section 1
, The maximum temperature and the minimum temperature data within the unit measurement period are extracted from the operation pattern from Step 2 and the temperature data from the A / D converter, and are calculated as ripple temperatures T1, T2, T3,.

The operation pattern PT and the ripple temperature T
1, T2, T3,... Are as shown in FIG. For example, if the electric motor 3 is an electric motor for driving an elevator, the time measuring unit 12 repeats the operation and the stop with the elevating period and the stop period, and further, repeats this operation in the operation having the operation period and the stop period on a daily basis. Are measured respectively. In the operation pattern PT of such operation and stop, one operation period and the subsequent stop period are set as a unit measurement period, and the ripple temperature detecting unit 13 calculates a difference between the maximum temperature and the minimum temperature for each unit measurement period. Temperature T1, T2, T3
... is calculated. Note that the ripple temperatures T1, T2, T
3,... Divide the assumed maximum temperature into several equal parts and set their temperature ranges. For example, the temperature is measured for each ripple temperature range at intervals of 5 degrees Celsius.

Next, the counter 14 counts the number of occurrences of the ripple temperature during each unit measurement period. For example, the number of occurrences of the ripple temperature T1 is n1 times, T2 is n2 times,... The counter 14 is initially reset at the time of the test of the apparatus and the test run thereof, and accumulates the respective count values as the apparatus operates at the site thereafter.

The cumulative damage rate calculation unit 15 estimates the life of the IGBT from the number of occurrences n1, n2, n3,... And the life number data (known) N1, N2, N3,. This estimation will be described below in principle.

The thermal fatigue life of the IGBT module due to solder deterioration is shown by a curve as shown in FIG. The vertical axis indicates the ripple temperature width (ΔT) of the copper base plate, and the horizontal axis indicates the number of repetitions (life times). In the case where the life curve of FIG. 3 is known in advance, if the number of occurrences for each ripple temperature is known, the life can be estimated using the following linear damage rule.

In FIG. 3, (1) It is assumed that the number of repetitions for each ripple temperature has been n1 times at T1, n2 times at T2, and n3 times at T3.

(2) The number of life cycles for each ripple temperature is N1 times at T1, N2 times at T2, and N times at T3.
Three times.

(3) The cumulative damage rate is defined by the following equation.

Cumulative damage rate CD = n1 / N1 + n2 / N2 + n3 / N3 where Δn / N (4) When cumulative damage rate CD = 1, it means that there is no remaining life. For example, if the cumulative damage rate calculated by the total number of cycles in one year is 1, the life is one year.

From the above, the cumulative damage rate calculation unit 15
Calculates the cumulative damage rate CD from the number of occurrences of the ripple temperature n1, n2, n3,... And the life number data (known).

The life calculator 16 calculates the life L = 1 / CD from the cumulative damage rate CD. What the life L means is
(N1 + N2 + N3 +... Tens Nn) is a magnification with respect to the total number of lifetimes. For example, when (N1 + N2 + N3 +... Tens Nn) is 100 times, if the cumulative damage rate at the current time is CD = 0.2, the life is L = 5. This means that the remaining life is five times (500 times) the elapsed period.

In practice, when the life L has been calculated, the remaining life is calculated according to the number of years up to the present time and the operating state. This remaining life has the relationship shown in FIG. 4, and by having a timer that counts up from the time of product shipment,
It is easy to calculate the failure prediction date.

As described above, according to the present embodiment, the life can be diagnosed based on the operation state of the device, the ripple temperature of the IGBT case and the number of occurrences can be estimated by a simple method, and the power cycle life can be further reduced. (2nd Embodiment) The unit measurement period in the above-described first embodiment is effective in the case where the operation is frequently stopped. But,
It has no effect on the life expectancy of a continuously operated device.

The present embodiment is effective for applications in which continuous operation is performed and load fluctuation is large. The unit measurement period is from the time when the measured temperature starts to rise to the time when the next rise starts. However, in practice, it is expected that the temperature will frequently rise and fall due to noise and minute load fluctuations. Therefore, hysteresis is provided for the judgment of the level of change in temperature rise and fall. For example, a temperature change within 20 ° C. can be ignored.

The configuration of the apparatus according to the present embodiment can be achieved by changing the processing function of the ripple temperature detector 13 in FIG. For example, as shown in FIG. 5, in the case of a device in which the operation pattern is a continuous operation and the energization current pattern changes, the case temperature of the IGBT has a rising period and a falling period even if the device is not stopped. Therefore, the change of the rise and fall of the temperature is detected by the ripple temperature detection unit 13,
Ripple temperatures T1, T2, and T at which the maximum temperature and the minimum temperature are obtained with one temperature increase and decrease as a unit measurement period.
Detected as 3,.

In the above embodiments, the temperature detector 10 detects the IGBT case temperature. However, it may be practically difficult to directly measure the case temperature. In that case, the temperature of the cooling fin can be estimated by using a thermistor attached for detecting overheating of the cooling fin temperature and using the thermal resistance between the base plate and the heat sink of the IGBT from the measured temperature of the cooling fin. For this estimation, for example, by multiplying the measured temperature rise value of the cooling fin by the thermal resistance, the base plate temperature rise value from the cooling fin can be calculated.

[0040]

As described above, according to the present invention, the ripple temperature of the base plate temperature of the main circuit element is measured for each unit measurement period, and the number of occurrences for each ripple temperature is counted for each unit measurement period. Since the life is estimated in accordance with the number of lifespans for each temperature range and the actual number of occurrences, the following effects are obtained.

(1) The life can be estimated by a simple method of counting the ripple temperature of the main circuit element case and the number of occurrences thereof.

(2) Since the remaining life can be estimated, the replacement time of the main circuit element can be accurately predicted.

(3) Since the life can be estimated in the operation state of the apparatus, the present invention is effective for an apparatus whose power cannot be turned off.

(4) The life estimation method does not require a sample analysis of the main circuit elements, and the life can be determined more quickly than in the conventional case.

[Brief description of the drawings]

FIG. 1 is an apparatus configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an operation pattern of the semiconductor power conversion device and a temperature ripple.

FIG. 3 is an example of a thermal fatigue life curve of an IGBT.

FIG. 4 is an explanatory diagram of a remaining life.

FIG. 5 is an example of a ripple temperature detection waveform according to another embodiment of the present invention.

[Explanation of symbols]

 2 Inverter 10 Temperature detector 11 A / D converter 12 Time measurement unit 13 Ripple temperature detection unit 14 Counter 15 Cumulative damage rate calculation unit 16 Life calculation unit

Claims (3)

[Claims] 1. A method for estimating the life of a semiconductor power conversion device using a power device as a main circuit element, comprising: directly measuring a base plate temperature of the main circuit element or estimating the base plate temperature from a cooling fin temperature of the main circuit element; The ripple temperature of the base plate temperature in the measurement period is measured for each temperature range, the number of occurrences for each of the ripple temperatures is counted for each unit measurement period, and the number of lifetimes N1, for the ripple temperature for each temperature range.
N2, N3,... And the actual number of occurrences n1, n2, n3,.
A life estimation method for a semiconductor power conversion device, wherein the life L is estimated according to the following equation: CD = (n1 / N1 + n2 / N2 + n3 / N3 +...) L = 1 / CD 2. A semiconductor power converter using a power device as a main circuit element, comprising: a temperature detecting means for directly measuring a base plate temperature of the main circuit element or estimating from a cooling fin temperature of the main circuit element; Ripple temperature detection means for measuring the ripple temperature of each temperature range from the base plate temperature detection value in the measurement period, counter means for counting the number of occurrences for each of the ripple temperatures for each unit measurement period, Life times N1,
N2, N3,... And the actual number of occurrences n1, n2, n3,.
From the following equation: CD = (n1 / N1 + n2 / N2 + n3 / N3 +...) L = 1 / CD 3. The unit measurement period may be a period from the start of operation of the semiconductor power conversion device to the start of the next operation, or a period from the time when the measured temperature starts to rise to the time when the measured temperature starts to rise next. The semiconductor power conversion device according to claim 2, wherein: