Automatic test method of portable frequency conversion serie

The maximum output voltage of the resonant device is 110KV, which is used for the AC voltage withstand test of 10kV and 35kV transformers, switches, buses and cross-linked cables. Considering the site test conditions and test requirements, the reactor parameters are 42kVA / 28kV / 99H, with a total of 4 sections, and the working frequency is 30 ~ 300Hz; the variable frequency control power supply is 10kW; the excitation transformer is 10KVA; the resonance quality factor is Q ≥ 30; The capacitor voltage divider is 120kv, the partial voltage ratio is 1000:1, and the capacitance of capacitor voltage divider is 0.06uF; the compensation capacitor is 120kV, 0.1uF, which is used for the AC withstand voltage test of transformer, switch and other equipment with small capacitance.
 
Automatic test (according to the set test parameters and stage parameters, it can automatically complete the frequency sweep, boost, withstand voltage and other test stages)
 
a) Start the program normally, welcome to the interface as shown in Figure 1
 

Figure 1 – instrument startup interface
 
Wait for two seconds to enter the main menu operation interface, as shown in Figure 2

Figure 2 – instrument main menu
 
Press up and down to move the cursor to the selected test item, and press the “OK” key to enter the selected item.

Figure 3 – Test Parameters
 
b) The test parameters are set as shown in Fig. 3
 
Test voltage: the highest voltage that can be reached during the test.
 
Partial pressure ratio: the ratio of voltage divider.
 
Excitation ratio: the transformation ratio of the excitation transformer, which is related to the resonance point found by frequency sweeping. When looking for the resonance point, if the resonance point has not been found and the instrument is suddenly disconnected, the resonance point can be found by changing the transformation ratio of the excitation transformer (increasing or decreasing).
 
Over voltage protection: when the high voltage exceeds this value, it usually does not exceed 1.1 times of the test voltage. Over current protection: when the current exceeds this value.
 
Sweep frequency range: search for the range of resonant frequency, divided into three sections: 20-55, 50-145,140-300.
 
Press the  key to move the cursor up and down to the parameter to be set, press the “voltage” of the rotating mouse to select the first digit of the parameter, press it again to move the selected position (cycle), and change the value of the parameter by adjusting the “voltage” of the rotating mouse left and right.
 
Press the “return” key to return to the previous menu or press the “OK” key to enter into the next level setting withstand voltage stage, as shown in Figure 4.
 
C) Setting the withstand voltage stage
 

Figure 4 – setting the automatic test withstand voltage stage
 
The automatic test is divided into 5 sections at most, and the target voltage of each section shall not exceed the “test voltage” set in “test parameters”. By rotating the mouse “voltage” to set the target voltage, rotating the mouse “frequency” to set the stage withstand voltage time.
 
Press “return” to return to the previous menu or press “OK” to enter the next level to start the test, as shown in Figure 5
 
d) Start automatic test

Figure 5 – automatic test interface
 
Display item description:
 
U peak value / √2: sample the peak value of AC high voltage U, and calculate the effective value of high voltage
 
U DC current: DC bus voltage
 
I output: output current
 
F output: system output frequency f, range: 30-300Hz
 
F measurement: system resonant frequency f (this frequency is only valid when the output frequency is near the resonance point or odd multiple frequency division)
 
Step number: output voltage regulation step number, full scale is 45000 steps
Over voltage: set over-voltage protection value
Over current: set the over-current protection value
Phase voltage: automatically test the target voltage of each stage
Withstand voltage time: the withstand voltage time of each stage will be tested automatically, and the countdown will start when withstand voltage
 
After confirming the parameters are correct, press the “start” key to start the test, and the test will be completed automatically according to the following steps:
 
1 = > the system automatically searches for the resonance point
2 = > adjust “U peak / √ 2” to phase target voltage
3 = > keep high voltage stable and withstand voltage for a long time
4 = > judge whether there is a next stage
5 = > if there is a next stage (target voltage and withstand time are not 0), skip to step 2 to continue the test
6 = > if there is no next stage, the voltage will be reduced automatically and the machine will be shut down
 
In the middle of the test, you can press the step-down stop key to depressurize and stop the machine directly in case of emergency (the “step-down stop” key and “emergency stop” key will only appear on the interface after the system is started).
 
(For more detailed operation and operation instructions, please refer to the operation manual of VF variable frequency power supply.)