JP3209004B2 - Power switching device life monitoring device and device using power switching device having same life monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus using a power switching element, and more particularly, to preventing the power switching element from being destroyed or grasping the maintenance time before the power switching element is destroyed by a power cycle. For technology.

[0002]

2. Description of the Related Art As an example of an apparatus using a power switching element, an inverter will be described with reference to FIG. FIG.
The inverter 2 includes a rectifier circuit 3, a smoothing circuit 4, and an inverter circuit 5, and the inverter circuit 5 includes an appropriate number of power switching elements 6 such as power transistors and IGBTs.

The operation of the inverter 2 is as follows. First, for example, a commercial three-phase AC is input from an AC input power supply 1 and converted into DC power by a rectifier circuit 3 and a smoothing circuit 4. Is converted into, for example, three-phase alternating current having a predetermined frequency by switching of a power switching element 6 in the inverter circuit 5, and is supplied to the motor 7. As a result, the motor 7 is driven at a rotation speed corresponding to the frequency of the AC power supplied from the inverter circuit 5.

A control circuit 10 for the inverter 2 includes a drive circuit 11 for a power switching element and an inverter control circuit 12, to which a command value 8 of the motor rotational speed is input, and a switch as an operation command device. An operation command 9a is input through 9. As an operation of the control circuit 10, while the switch 9 is on, a timing for turning on / off each power switching element 6 necessary for the inverter circuit 5 to generate AC power having a frequency corresponding to the command value 8. The inverter control circuit 12 generates a control signal according to the command value 8, and the drive circuit 11 amplifies the timing control signal to a level necessary for the power switching element 6 to be turned on / off. Is turned on / off. That is, while the switch 9 is on, the inverter 2 is in the operating state, and the motor 7 rotates. While the switch 9 is off, the inverter control circuit 12 generates a control signal for turning off all the power switching elements 6 in the inverter circuit 5. That is, while the switch 9 is off, the inverter 2 is stopped, and the motor 7 stops.

[0005]

However, conventionally, in an apparatus using a power switching element such as an inverter 2,
Since the life of the power switching element due to the power cycle is not considered, there is a problem in that the life cannot be known until the element is destroyed.

<Explanation of Power Cycle> Here, the power cycle will be described. (1) First, in a device using a power switching element such as the inverter 2, when the device is operated, the power switching element generates heat and the junction temperature of the chip rises. When the device is stopped, the heat stops and the junction temperature decreases. descend. Therefore, the chip portion of the power switching element repeats thermal expansion and thermal contraction due to repetition of operation and stop. (2) On the other hand, since the power switching element is generally assembled using various materials having different coefficients of thermal expansion, especially when the temperature of the bonding wire rises due to the heat generated by the power switching element, the encapsulation, which is the coating agent for the chip, is reduced. The bonding wire starts to be gradually separated from the chip due to the thermal expansion stress, and finally the bonding wire is completely separated and becomes an open state by repeating the operation and stop of the device. That is, the power switching element is defective or destroyed. (3) A cycle of thermal expansion and thermal contraction until the bonding wire is completely peeled off by thermal expansion stress and leads to failure or destruction is called a power cycle.

[0007] Therefore, in a device having a high repetition frequency of operation and stop such as when the inverter 2 is used for driving an AC servo device or an elevator motor, the life of the power switching element is shortened by the power cycle. is necessary.

In view of the above circumstances, the present invention monitors the life of a power switching element due to a power cycle, grasps the maintenance time of the power switching element before the life is over, and prevents the element from being destroyed. It is an object to provide a device that enables it.

[0009]

A first aspect of the present invention for achieving the above object is as follows.
The life monitoring device for a power switching element according to the invention comprises a life estimation means for estimating the life of the power switching element by a power cycle, and a protection instruction for outputting a signal for instructing protection of the power switching element before reaching the estimated life. Means for a power switching element comprising
In the life monitoring device, the life estimating means may include the power
ー The junction temperature of the switching element chip
Power difference and the same power switching as junction temperature difference
The relationship between the power cycle of the element and the power cycle
Storage means stored as the
Between operation and shutdown of equipment using
As the junction temperature difference of the power switching element
Enter the setting value and the power cycle corresponding to this setting value
From the power cycle characteristics of the storage means.
Including computing means for the life of the switching element,
The protection instruction means is used by the power switching element.
Counts the number of times the equipment has been
Counting means for outputting a protection instruction signal when the value is exceeded;
The power cycle obtained from the power cycle characteristics of the storage means
Calculation means for multiplying a vehicle by a count less than 1 to obtain the reference value
It is characterized by including .

[0010]

Furthermore, life monitoring equipment of the power switching device according to the second invention, the counting means is characterized in that for outputting alarm signal as the protective finger <br/> No.示信.

Still further, in the power switching element life monitoring apparatus according to a third aspect of the present invention, the counting means includes the storage means.
It is characterized in that for outputting a trip signal for stopping <br/> device using the power switching element as a protection indication signal.

On the other hand, a device using a power switching element according to a fourth invention for achieving the above object is a device according to the first invention.
Alternatively, a life monitoring device for a power switching element according to the second invention is provided.

An apparatus using a power switching element according to a fifth aspect of the present invention includes a power switching element life monitoring apparatus according to a third aspect of the present invention, and a control means for stopping operation by a trip signal of the life switching apparatus. , Are provided.

[0015]

According to the first aspect, basically, the life of the power switching element is estimated by a power cycle, and a protection instruction signal is output before reaching the life. By using this protection instruction signal, before the power switching element is destroyed, it can be determined that maintenance is necessary to replace the element with a new one, or the operation of the device using the element is stopped and Destruction can be prevented.

In particular, in the first invention, the life is estimated using the power cycle characteristics of the power switching element. That is, when the apparatus using the power switching element is operated and stopped, a temperature difference occurs in the junction temperature of the chip of the power switching element as described above. The power cycle has a deep correlation with this junction temperature difference. As illustrated in FIG. 2, as the junction temperature difference ΔT _j is higher, the power cycle C _p is shorter (short life), and as the junction temperature difference ΔT _j is lower, the power cycle is lower. cycle C _p is a power cycle characteristics of long (long life). Therefore, the power cycle characteristics as shown in FIG. 2 are prepared in advance based on the technical data of the power switching element to be used, or through experiments, and the junction temperature difference ΔT _j is set. The life of the switching element can be estimated. And estimate the life of the power switching element
Multiplied by a factor less than 1 to the reference value
And the number of operation of the device using the power switching element
Outputs a protection instruction signal when exceeds the reference value. The junction temperature difference ΔT _j can be obtained by experimentally operating and stopping the device using the power switching element, or by calculating from the power loss of the power switching element and the heat radiation characteristics in the same device. Can also. However, it is preferable that the value of the junction temperature difference ΔT _{j be} a fixed value by selecting a representative point in operation and stop of the device. This is the junction temperature difference ΔT
The value of _j usually changes, but when the value of ΔT _j changes, FIG.
It is extremely difficult to calculate the life from the power cycle characteristics as described above, and a large error does not occur even if a representative value is used.

In the second invention, an alarm signal is output as a protection instruction signal . By using this alarm signal,
Before destruction of the power switching element, it is possible to judge that it is time for maintenance to replace the element with a new one, or to stop the operation of the device using the element to prevent destruction of the element.

In the third invention, a trip signal is output as a protection instruction signal . By using this trip signal, it is possible to stop the operation of the device using the power switching element and prevent the destruction of the element before the power switching element is destroyed. It is also possible.

According to the fourth aspect of the present invention, since the life monitoring device for the power switching element is provided, before the power switching element in use is destroyed, it is determined that the maintenance time is required to replace the element with a new one. It is possible to prevent the destruction of the device by stopping the operation of the device using the device.

According to the fifth aspect of the present invention, since the life monitoring device for outputting the trip signal and the control means for stopping the operation by the trip signal are provided, the power switching element in use is destroyed before the element is destroyed. The operation of the device using the device is automatically stopped to prevent the device from being destroyed.
At this time, the power switching element can be replaced with a new one.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention and an embodiment thereof will be described below with reference to the drawings. FIG. 1 shows an inverter 2 together with a control circuit 10 and a life monitoring device 20 as an example of a device using a power switching element.

In FIG. 1, the inverter 2 comprises a rectifier circuit 3, a smoothing circuit 4, and an inverter circuit 5 as in the conventional example. The inverter circuit 5 includes an appropriate number of power switching elements 6 such as power transistors and IGBTs. ing. The operation of the inverter 2 is the same as that of the conventional example. First, for example, a commercial three-phase AC is input from the AC input power supply 1 and converted into DC power by the current circuit 3 and the smoothing circuit 4. The DC power is supplied to, for example, 3 by the switching of the power switching element 6 in the inverter circuit 5.
The phase is converted into an alternating current having a predetermined frequency, and is supplied to the motor 7. As a result, the motor 7 is driven at a rotation speed corresponding to the frequency of the AC power supplied from the inverter circuit 5.

The control circuit 10 for the inverter 2 has a drive circuit 11 for the power switching element as in the prior art.
And an inverter control circuit 12. The inverter control circuit 12 not only receives a motor rotation speed command value 8 and also receives an operation command 9a through a switch 9 as an operation command device. As described above, the alarm signal 13a and the trip signal 14a are input from the life monitoring device 20. Further, reset signals 12a and 12b are output from the inverter control circuit 12 to the life monitoring device 20 as control signals as described later.

The operation of the control circuit 10 is basically the same as that of the conventional example, and while the switch 9 is on, each power switching required for the inverter circuit 5 to generate AC power of a frequency corresponding to the command value 8 is performed. The inverter control circuit 12 generates a timing control signal for turning on / off the element 6 according to the command value 8, and converts the timing control signal to a level required for the power switching element 6 to turn on / off. The drive circuit 11 amplifies and turns on / off the power switching element 6. That is, while the switch 9 is on, the inverter 2 is in the operating state, and the motor 7 rotates. However, when the trip signal 14a is input even while the switch 9 is on, the inverter control circuit 12 generates a control signal for turning off all the power switch elements 6, and forcibly stops the inverter 2.
When the alarm signal 13a is input, the inverter control circuit 12 activates an alarm (not shown) to notify the staff that the time to maintain the power switching element 6 has come by sound or light emission, Prompt for replacement. When the power switching element 6 is replaced with a new one, a person in charge of the replacement is input by a reset switch or the like (not shown), so that the inverter control circuit 12 outputs the reset signals 12a and 12b to the life monitoring device 20.

While the switch 9 is off, the inverter control circuit 12 generates a control signal for turning off all the power switching elements 6 in the inverter circuit 5 as in the prior art. That is, when the switch 9 is off, the inverter 2 is stopped, and the motor 7 stops.

<Life monitoring device for power switching element>
> The life monitoring device 20 includes the counter 13 and the counter 14
The reference value calculation circuit 15 and the memory (table) 16
Each of the counters 13 and 14 has an operation command device 9.
The operation command 9a is inputted every time the switch is turned on, and the reference value calculation circuit 15
From the reference value K₁C_P, K_TwoC_PIs entered and
Reset signals 12a and 12b are input from the data control circuit 12.
Is forced. The reference value calculation circuit 15 has a junction.
Temperature difference ΔT _jInput circuit 19 for setting and calculation of reference value
Coefficient K₁, K_TwoInput circuits 17 and 18 for setting are connected
ing.

First, in the memory 16, the power cycle characteristics of the power switching element 6 used in the inverter 2, that is, the junction temperature ΔT as shown in FIG.
correlation between the _j and the power cycle C _P are stored in the form of a table in advance.

The reference value calculation circuit 15 is operated by the input circuit 19.
Junction temperature difference ΔT_jIs set,
Junction temperature difference ΔT_jPower cycle C corresponding to
_PIs read from the memory 16 and the power switching element
Estimated as 6 life. Further, the reference value calculation circuit 15
Is calculated by the input circuit 17 using the coefficient K₁(0 <K₁<1) is set
Power cycle C_PTo the coefficient K₁Multiplied by
The value of K₁C_PTo the counter 13 as the alarm reference value.
You. Similarly, the coefficient K_Two(K₁<K_Two
When <1) is set, the power cycle C_PTo the coefficient K_Two
, And the value K _TwoC_PThe trip reference value
To the printer 14.

The counter 13 is of a count-up type, and has a reference value K ₁ C supplied from a reference value calculation circuit 15.
_P is set as a set value, and the number of times the operation command 9a input each time the switch 9 is turned on is counted as the number of operations. When the count value C _C increases and exceeds the set value (reference value) K ₁ C _P , , And outputs the alarm signal 13a to the inverter control circuit 12 and the outside. When the reset signal 12a is input from the inverter control circuit 12, the counter 13 stops the alarm signal and simultaneously returns the count value to zero.

The counter 14 is a same as the count-up type, the reference value K ₂ C _P supplied from the reference value calculation circuit 15 as the set value, the number of inputs of the operation command 9a inputted to each on of the switch 9 Is counted as the number of operations, the count value C _C increases, and the set value (reference value) K ₂ C
When it exceeds _P , a trip signal 14a is output to the inverter control circuit 12 and the outside. When the reset signal 12b is input from the inverter control circuit 12, the counter 14 stops the trip signal and simultaneously returns the count value to zero.

<How to Use the Life Monitoring Device> Next, an example of how to use the life monitoring device 20 will be described. (1) First, the power cycle characteristics are stored in the memory 16. (2) Next, a representative value (fixed value) of the junction temperature difference ΔT _j is determined based on the power loss calculation, and is set in the reference value calculation circuit 15 by the input circuit 19. (3) Next, the coefficient K ₁ is set in a range of 0.7 ≦ K ₁ ≦ 0.8, and the coefficient K ₂ is set in a range of 0.9 ≦ K ₂ <1.0, for example. Is set in the reference value calculation circuit 15 by (4) After that, the operating frequency C _C of the inverter 2 counter 13 counts, since the counter 13 when the K ₁ C _P <C _C outputs an alarm signal 13a, the inverter according to the clerk alarm 2 Is stopped, and the power switching element 6 is replaced with a new one as soon as possible. At this time, the counters 13 and 14 are reset by operating a reset switch or the like. As a result, the number of times of operation is restarted from the restart of operation. (5) If the alarm signal 13a is output and left as it is, the alarm continues, and in the meantime, the counter 14 sets the K ₂ C _P <
At the time of _CC , the trip signal 14a is output, and the operation of the inverter 2 is automatically stopped by this. Therefore, the attendant replaces the power switching element 6 with a new one. At this time, the counters 13 and 14 are reset by operating the reset switch and the like. As a result, the number of operations is counted again from the restart of operation after replacement.

In FIG. 1, although the inverter 2, the control circuit 10, and the life monitoring device 20 appear to be separate, the control circuit 10 and the life monitoring device 20 may be provided inside the inverter 2, or It may be provided outside the inverter 2.

[0033]

Effect of the Invention According to the first invention, basically, the life of the power <br/> switching element estimated by the power cycle, since outputs a protection instruction signal before reaching the life, the protection instruction Before the destruction of the power switching element using the signal, judge that it is time to replace the element with a new one, or stop the operation of the device using the element to prevent the destruction of the element. Becomes possible.

In particular, according to the first invention, the life cycle is estimated by obtaining the power cycle corresponding to the set value input as the junction temperature difference from the power cycle characteristic of the power switching element, so that the life estimation is easy. And easy. In addition, the power switching element
Multiply the estimated power cycle by a factor less than 1
By setting it to the reference value, the power switching element
When the number of operation of the used equipment exceeds the reference value, the protection instruction
A signal can be output.

[0035] According to the second invention, since the output <br/> alarm signal as protection instruction signal, before the destruction of the power switching device by using the warning signal, to be replaced by the same device with a new maintenance It is possible to prevent the destruction of the element by judging the timing of the element and stopping the operation of the device using the element.

According to the third aspect of the present invention, the trip signal is output as the protection instruction signal. Therefore, before the power switching element is destroyed by using the trip signal, the operation of the apparatus using the element is performed. Can be forcibly stopped to prevent the destruction of the element.

According to the fourth aspect of the present invention, since the life monitoring device for the power switching element is provided, before the power switching element in use is destroyed, it is determined that it is time for maintenance to replace the element with a new one. or, it is possible to prevent the destruction of the device to stop the operation of the apparatus that have used the same elements.

According to the fifth aspect of the present invention, since the life monitoring device for outputting the trip signal and the control means for stopping the operation by the trip signal are provided, the power switching element in use is destroyed before the element is destroyed. The operation of the device using the device is automatically stopped to prevent the device from being destroyed.
At this time, the power switching element can be replaced with a new one.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing power cycle characteristics.

FIG. 3 is a diagram showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 AC input power supply 2 Inverter 3 Rectifier circuit 4 Smoothing circuit 5 Inverter circuit 6 Power switching element 7 Motor 8 Command value of rotation speed 9 Operation commander (switch) 9a Operation command 10 Control circuit 11 Drive circuit 12 Inverter control circuit 12a, 12b Reset signal 13 Counter (counting means) 13a Alarm signal 14 Counter (counting means) 14a Trip signal 15 Reference value calculation circuit (calculation means) 16 Memory (storage means) 17, 18 Coefficient setting input circuit 19 Junction temperature difference setting input circuit 20 life monitoring device C _P power cycle [Delta] T _j junction temperature difference K _1, K ₂ coefficients _{K 1 C P, K 2 C} P reference value

Claims (5)

(57) [Claims] 1. A and lifetime estimation means for estimating the life due to the power cycle of the power switching elements, power over switching to and a protection instruction means for outputting a signal indicative of protection of the power switching element before reaching the estimated lifetime In the device life monitoring device , the life estimating means includes a power switching device chip.
Temperature difference of the junction temperature of the
Temperature difference and power cycle of power switching element
Memory that previously stores the relationship of
And the device in which the power switching element is used
Power switching element during operation and shutdown
Enter the set value as the junction temperature difference for
The power cycle corresponding to the fixed value is determined by the power of the storage means.
Life of power switching element obtained from cycle characteristics
The protection instruction means is used by the power switching element.
The number of operation of the installed equipment is counted, and the counted
Counting means for outputting a protection instruction signal when the threshold value is exceeded,
The power sensor determined from the power cycle characteristics of the storage means
A calculation operator who multiplies the cycle by a count less than 1 and sets the reference value.
An apparatus for monitoring the life of a power switching element , comprising a step . Wherein said counting means, life monitoring apparatus of the power switching device of claim 1, wherein the outputting the alarm signal as the protection instruction signal. Wherein said counting means, life monitoring apparatus of the power switching device according to claim 1, characterized in that for outputting a trip signal for stopping the apparatus using the power switching element as the protection instruction signal. 4. A device using the power switching element characterized by comprising a life monitoring system of the power switching device according to claim 1 or 2. 5. A power switching element, comprising: a life monitoring device for a power switching element according to claim 3; and control means for stopping operation by a trip signal of the life monitoring apparatus. apparatus.