在變頻器日常維護過程中,經常遇到各種各樣的問題,如外圍線路問題,參數設定不良或機械故障。如果是變頻器出現故障，如何去判斷是哪一部分問題，在這里略作介紹。

 

　　一、靜態(tài)測試

 

　　1、測試整流電路

 

　　找到變頻器內部直流電源的P端和N端，將萬用表調到電阻X10檔，紅表棒接到P，黑表棒分別依到R、S、T，應該有大約幾十歐的阻值，且基本平衡。相反將黑表棒接到端，紅表棒依次接到R、S、T，有一個接近于無窮大的阻值。將紅表棒接到N端，重復

 

　　以上步驟，都應得到相同結果。如果有以下結果，可以判定電路已出現異常，A.阻值三相不平衡，可以說明整流橋故障。B.紅表棒接P端時，電阻無窮大，可以斷定整流橋故障或起動電阻出現故障。

 

　　2、測試逆變電路

 

　　將紅表棒接到P端,黑表棒分別接U、V、W上，應該有幾十歐的阻值，且各相阻值基本相同，反相應該為無窮大。將黑表棒接到N端，重復以上步驟應得到相同結果，否則可確定逆變模塊故障.

 

　　二、動態(tài)測試

　　在靜態(tài)測試結果正常以后，才可進行動態(tài)測試，即上電試機。在上電前后必須注意以下幾點:

 

　　1、上電之前，須確認輸入電壓是否有誤，將380V電源接入220V級變頻器之中會出現炸機（炸電容、壓敏電阻、模塊等）。

 

　　2、檢查變頻器各接播口是否已正確連接,連接是否有松動,連接異常有時可能導致變頻器出現故障,嚴重時會出現炸機等情況。

 

　　3、上電后檢測故障顯示內容,并初步斷定故障及原因。

 

　　4、如未顯示故障,首先檢查參數是否有異常,并將參數復歸后,進行空載(不接電機)情況下啟動變頻器,并測試U、V、W三相輸出電壓值。如出現缺相、三相不平衡等情況，則模塊或驅動板等有故障

 

　　5、在輸出電壓正常（無缺相、三相平衡）的情況下，帶載測試。測試時，最好是滿負載測試。

 

　　三、故障判斷

 

　　1、整流模塊損壞

 

　　一般是由于電網電壓或內部短路引起。在排除內部短路情況下，更換整流橋。在現場處理故障時，應重點檢查用戶電網情況，如電網電壓，有無電焊機等對電網有污染的設備等。

 

　　2、逆變模塊損壞

 

　　一般是由于電機或電纜損壞及驅動電路故障引起。在修復驅動電路之后，測驅動波形良好狀態(tài)下，更換模塊。在現場服務中更換驅動板之后，還必須注意檢查馬達及連接電纜。在確定無任何故障下，運行變頻器。

 

　　3、上電無顯示

 

　　一般是由于開關電源損壞或軟充電電路損壞使直流電路無直流電引起，如啟動電阻損壞，也有可能是面板損壞。

 

　　4、上電后顯示過電壓或欠電壓

 

　　一般由于輸入缺相，電路老化及電路板受潮引起。找出其電壓檢測電路及檢測點，更換損壞的器件。

 

　　5、上電后顯示過電流或接地短路

 

　　一般是由于電流檢測電路損壞。如霍爾元件、運放等。

 

　　6、啟動顯示過電流

 

　　一般是由于驅動電路或逆變模塊損壞引起。

 

　　7、空載輸出電壓正常,帶載后顯示過載或過電流該種情況一般是由于參數設置不當或驅動電路老化,模塊損傷引起。

In the daily maintenance process of frequency converter, we often encounter a variety of problems, such as peripheral circuit problems, poor parameter setting or mechanical failure. If the frequency converter fails, how to determine which part of the problem is briefly introduced here.

 

 

 

1、 Static test

 

 

 

1. Test rectifier circuit

 

 

 

Find the p-terminal and N-terminal of the DC power supply inside the converter, adjust the multimeter to the resistance X10, connect the red meter rod to the P, and press the black meter rod to the R, s and t respectively, which should have a resistance value of about tens of ohms and be basically balanced. On the contrary, connect the black meter rod to the end, and connect the red meter rod to R, s and t successively, with a resistance value close to infinity. Connect the red indicator rod to the N end, repeat

 

 

 

All the above steps should get the same result. If there are the following results, it can be determined that the circuit has been abnormal. A. the three-phase imbalance of resistance value can indicate the fault of rectifier bridge. B. When the red meter bar is connected to the p-terminal, the resistance is infinite, so it can be concluded that the rectifier bridge is faulty or the starting resistance is faulty.

 

 

 

2. Test inverter circuit

 

 

 

Connect the red meter rod to the P end, and connect the black meter rod to the U, V and W respectively. There should be several tens of ohm resistance values, and the resistance values of each phase are basically the same, and the reverse phase should be infinite. Connect the black meter bar to the N terminal, repeat the above steps to get the same result, otherwise the inverter module fault can be determined

 

 

 

2、 Dynamic test

 

 

 

After the static test results are normal, the dynamic test can be carried out, that is, power on the test machine. Pay attention to the following points before and after power on:

 

 

 

1. Before power on, it is necessary to confirm whether the input voltage is wrong. If the 380V power supply is connected to the 220V frequency converter, there will be explosion (explosion capacitance, varistor, module, etc.).

 

 

 

2. Check whether the connectors of the frequency converter have been connected correctly, whether the connection is loose, and if the connection is abnormal, the frequency converter may sometimes fail, or even explode.

 

 

 

3. After power on, detect the fault display content and preliminarily determine the fault and cause.

 

 

 

4. If no fault is displayed, first check whether the parameters are abnormal, and reset the parameters, start the inverter under no-load (without motor), and test the output voltage of u, V, w three-phase. In case of phase loss, three-phase imbalance, etc., the module or drive board is faulty

 

 

 

5. Under the condition that the output voltage is normal (no phase loss, three-phase balance), carry out on load test. When testing, it is best to test at full load.

 

 

 

3、 Fault judgment

 

 

 

1. Rectifier module damaged

 

 

 

Generally, it is caused by grid voltage or internal short circuit. Replace the rectifier bridge when the internal short circuit is eliminated. When dealing with faults on site, it is important to check the power grid of users, such as the power grid voltage, whether there are welding machines and other equipment that pollute the power grid.

 

 

 

2. Inverter module damaged

 

 

 

Generally, it is caused by motor or cable damage and drive circuit failure. After repairing the driver circuit, replace the module when the driver waveform is in good condition. After replacing the drive board in the field service, the motor and connecting cable must also be checked. Run the frequency converter without any fault.

 

 

 

3. No display when power on

 

 

 

Generally, it is caused by the damage of switching power supply or soft charging circuit, which makes the DC circuit free of DC. If the starting resistance is damaged, it may also be panel damage.

 

 

 

4. Overvoltage or undervoltage displayed after power on

 

 

 

Generally, it is caused by input phase loss, circuit aging and circuit board damp. Find out the voltage detection circuit and detection point, and replace the damaged device.

 

 

 

5. Over current or short circuit to ground after power on

 

 

 

Generally, the current detection circuit is damaged. Such as hall element, operational amplifier, etc.

 

 

 

6. Start display overcurrent

 

 

 

Generally, it is caused by the damage of driving circuit or inverter module.

 

 

 

7. No load output voltage is normal, overload or over-current will be displayed after load, which is generally caused by improper parameter setting or aging of driving circuit and module damage.