JP2002095155A - Cooling system maintenance method of static power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate an alarm before abnormality advances too much when an abnormality occurs in a cooling system of an inverter. SOLUTION: From a temperature of a part position having correlation to the environmental temperature of a cooling body, the environmental temperature is obtained at every moment by operation. The temperature rise amount of the cooling body which is obtained by operation from the quantity of generated heat is added to the environmental temperature. Consequently, a cooling body theoretical temperature is estimated. The theoretical temperature is compared with the cooling body temperature which is measured actually with a detector. When the difference exceeds a reference value, an alarm is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting an abnormality in a cooling system in a static power converter such as an inverter for variable speed driving, which includes a semiconductor power converter such as an insulated gate bipolar transistor (IGBT). The present invention relates to a method for maintaining a cooling system such as determining when to replace parts.

[0002]

2. Description of the Related Art In this type of power converter, a semiconductor power conversion element is mounted on a cooling body having a large number of cooling fins, and these elements are connected so as to form a converter or an inverter. In addition, they are usually incorporated into one case together with a control circuit of an inverter, a temperature detecting element, and the like, and are unitized.

FIG. 2 shows an internal basic circuit configuration of this type of inverter unit 1. An AC input from a commercial power supply AC is converted to a direct current by a converter section CV comprising a rectifier, and is charged into an intermediate capacitor C. You. Inside the inverter unit 1, there is a control circuit CTR, IG
An AC output is supplied to a load, for example, a motor M by controlling an inverter unit INV including a semiconductor power conversion element (switching element) such as a BT.

The control circuit CTR receives detection signals from the output current detection element 2, the cooling body temperature detection element 3, the unit temperature detection element 4, and the like.

[0005] Steady-state loss (loss when main circuit current is flowing) and switching loss (loss generated when main circuit current is turned on and off) of IGBTs that are components such as inverters.
Is transmitted to the above-described cooling fins, and is often exhausted by a cooling fan.

In this case, from the viewpoint of preventing thermal destruction of the semiconductor element, it is necessary to measure or estimate the junction temperature of the semiconductor element as accurately as possible. Techniques for doing this are known. For example, JP-A-7-13573
In No. 1, in order to estimate a junction temperature of a semiconductor element, a current value flowing through the element and a terminal voltage value are measured, and a case temperature or a cooling body temperature is added.

However, components that must be considered thermally in a power converter are not limited to semiconductor elements. For example, the image of the spatial arrangement of each component in FIG. 2 is as illustrated in FIG. 3, but in the unit internal space 6 isolated from the outside air by the case 5, the IGB
An element 7 such as T and a control circuit 9 are placed, and the element 7 is thermally coupled to a cooling body 8 having a fin structure.

In this case, not all the heat generated by the element 7 is exhausted by the cooling body 8, so that the temperature of the unit internal space 6 necessarily increases. Since the control circuit 9 contains electronic components sensitive to temperature, such as a microcomputer, when the internal temperature reaches a temperature at which normal operation of these electronic components cannot be ensured,
Even if the semiconductor element itself can withstand heat, the inverter must be stopped and an alarm such as "abnormal ambient temperature" must be issued.

For this reason, conventionally, as shown in FIG. 4, the temperature measurement values from the cooling body temperature detecting element and the unit internal temperature detecting element are compared with respective abnormal levels by a comparator, and one of them is set to an abnormal level. When it reaches, the alarm circuit operates to generate an alarm output and stop the inverter.

However, conventionally, the abnormal level value, which is the comparison value, is set to the worst value (the maximum allowable operating temperature,
Normally, the abnormality judgment is made in accordance with 40 ° C., so at the actual ambient temperature (less than 40 ° C.), the cooling system is abnormal (cooling fan speed decrease, cooling fin clogging, etc.). ) Often progresses too far and an alarm is issued. For example, when an inverter is used in a material processing system, the system must be shut down due to an unexpected stoppage of the inverter, resulting in damage to the material being processed or damage to the material. Since an adverse effect such as a delay in the entire work process may occur, it is required to issue an alarm at an earlier point in time.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to predict the occurrence of abnormality at an earlier point in time by estimating the amount of heat generated, the temperature of the cooling fins, the temperature inside the unit, etc. based on the output current of the inverter. It is an object of the present invention to provide a cooling system abnormality monitoring method capable of performing the following.

[0012]

According to the present invention, the ambient temperature of the cooling system is estimated from the temperature detection values of other parts by calculation.
The temperature rise is added to the ambient temperature to obtain a cooling body theoretical temperature, and the theoretical temperature is compared with the cooling body temperature actually measured by the detector. If the difference exceeds a reference value, an alarm is issued.

To be more precise, the present invention relates to a static power converter unitized to include a semiconductor power conversion element thermally coupled to a cooling body, and to generate a heat quantity from an output current of the converter. It calculates and calculates the temperature rise of the cooling body and the temperature rise inside the unit based on the result, and estimates and calculates the theoretical temperature of the cooling body from the output temperature estimation calculation inside the unit and the temperature measurement output inside the unit.
It is characterized in that a sum of a cooling body rise temperature estimation calculation output and a cooling body theoretical temperature estimation calculation output and a cooling body temperature measurement output are compared to issue an alarm.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 for explaining the principle of the present invention, an inverter (not shown) is similar to FIG.
An output current detecting element, a unit internal temperature detecting element, and a cooling body temperature detecting element are provided.

The amount of heat W generated by the semiconductor element constituting the inverter is obtained by calculation from the inverter output current I detected by the current detecting element 2 such as a current transformer. The amount of heat W generated by the inverter raises the temperature of the cooling body and at the same time raises the internal temperature of the unit.

In an actual inverter unit, the temperature rise ΔTf of the cooling body and the temperature rise ΔTu inside the unit
Are functions of the generated heat amount W, and each function in a normal state of the cooling system can be obtained theoretically or experimentally. In the present embodiment, ΔTf and ΔTu are calculated by using a generated heat amount W as an input by an arithmetic circuit based on this function.

From the unit internal temperature Tu detected by the unit internal temperature detecting element 4 such as a thermistor, the unit internal temperature rise ΔTu estimated by calculation from the output current detection value I is subtracted to obtain the estimated ambient temperature Ta of the cooling body. Is calculated. By adding the aforementioned ΔTf to the estimated ambient temperature Ta, the cooling body temperature Tf that depends on the output current I and the ambient temperature Ta is estimated.

Then, the estimated temperature Tf of the cooling body derived from the calculation and the actual cooling body temperature Tc directly detected by the detecting element
Are compared by a comparator, and an alarm is generated when this difference exceeds a reference value.

In the above abnormality judgment, the measured temperature T of the cooling body
As a reference value for comparison with c, a theoretical estimated value Tf in which the ambient temperature is included in the calculation is applied. In other words, instead of fixing the numerical value of the ambient temperature to the design worst value (allowable maximum operating temperature, usually 40 ° C.) as in the conventional inverter, and determining the abnormality judgment reference value, the actual ambient temperature at every moment is taken into account. Since the determination is made, an alarm can be issued before the abnormality proceeds.

Also, instead of the unit internal temperature Tu,
Ambient temperature Ta is estimated by calculation from the detected temperature of another part having a correlation with the ambient temperature of the cooling body, and thereafter, cooling body temperature Tf is estimated in the same manner as described above (that is, Tf = Ta +
ΔTf), and a method of performing a comparison process with the measured cooling body temperature Tc can obtain the same effect.

In any of the above methods, the reference value may be a practically fixed value, or a plurality of reference values corresponding to the magnitude of the output current value are prepared to perform the alarm generation operation. You may decide.

In any of the above cases, the reference value for generating an alarm is set to a value lower than the reference value for generating a stop signal (set value described in the conventional method). Thus, maintenance can be called out before the system suddenly stops.

[0023]

According to the present invention, when any abnormality occurs in the cooling system of the inverter while the system is operating,
An alarm is issued before the abnormality progresses too much, so that the system can be shut down in an orderly manner, thereby avoiding damage caused by a sudden stop, and furthermore, it is possible to avoid unnecessary labor for maintenance due to delay.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining the principle of the present invention.

FIG. 2 is a basic configuration diagram of a general inverter unit.

FIG. 3 is a structural conceptual diagram of an inverter unit.

FIG. 4 is a block diagram of a conventional alarm signal system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter unit 2 Output current detecting element 3 Cooling element temperature detecting element 4 Unit internal temperature detecting element 5 Case 6 Unit internal space 7 Elements such as IGBT 8 Cooling element 9 Control circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02M 1/00 H01L 27/04 H 7/48 F term (Reference) 5F038 AZ02 AZ08 BH16 DF01 DF14 EZ20 5G053 AA14 BA01 BA06 CA08 DA03 EA01 EB01 EC02 FA04 5H007 AA05 AA17 CA01 DB02 DC02 DC08 FA13 HA05 5H740 AA08 BA11 BB05 BB10 MM08 MM11 PP06

Claims (1)

[Claims] In a static power conversion device unitized including a semiconductor power conversion element thermally coupled to a cooling body, the amount of heat generated is calculated from the output current of the conversion device, and based on the result, Estimate and calculate the temperature rise of the cooling body and the temperature rise inside the unit. A cooling system maintenance method for a stationary power converter, wherein a sum of a temperature estimation calculation output and a cooling body temperature measurement output are compared to issue an alarm.