The variable frequency dielectric loss tester starts measurement, the high voltage set value is sent to the variable frequency power supply, which uses PID algorithm to slowly adjust the output to the set value. The measurement circuit sends the actual high voltage to the variable frequency power supply, fine-tuning the low voltage to achieve accurate high voltage output. According to the positive/reverse wiring settings, the measurement circuit automatically selects the input and switches the range based on the test current. The measurement circuit uses Fourier transform to filter out interference, separates the fundamental wave of the signal, performs vector operations on the standard current and the test sample current, calculates capacitance from amplitude, and calculates tgδ from phase difference. Multiple measurements are repeated, and a middle result is selected after sorting. After measurement, the measurement circuit issues a voltage reduction command, and the variable frequency power supply slowly reduces voltage to 0.
Precautions and Others
Precautions
1. This instrument can only be used on equipment that is powered off; the grounding terminal should be reliably connected to the grounding grid,
The instrument should be used in a spacious, safe, and reliable place as much as possible.
2. The equipment under test should be disconnected from the high-voltage leads from the operating state and switched to maintenance state, and after cleaning and preliminary insulation test is good, the instrument can be used for testing to prevent damage to the instrument during voltage application due to poor insulation of the equipment under test.
3. Determine the wiring method according to the installation situation of the equipment, and select the wiring method in the corresponding menu options.
4. Correctly select the test voltage level according to different equipment, and select the required voltage in the corresponding menu options.
5. If a special situation endangering safety occurs during the test, the main power can be urgently turned off.
6. Only after disconnecting the power switch on the panel and clearly disconnecting the 220V test power supply can wiring changes be made or work be completed; when repeating the test on the same test equipment, you can press reset and measure again, or choose to repeat after the previous test is completed.
7. To ensure measurement accuracy, especially when the loss of small capacitance test samples is small, it is necessary to ensure that the low-voltage end (or secondary end) of the equipment under test has good insulation, and measure in an environment with relatively low humidity.
8. When conducting experiments with large capacitance test samples, the grounding of the instrument and the grounding of the test sample should not be at the same grounding point to prevent the counterattack voltage or traveling wave from affecting the safety of the instrument during grounding discharge.
9. The instrument comes with a voltage boosting device; attention should be paid to the insulation distance of the high-voltage lead and personnel safety; 10. The instrument should be reliably grounded; poor grounding may cause machine protection or danger.
10. After the instrument is started, except for special circumstances, it is not allowed to suddenly turn off the power to avoid overvoltage damage to the equipment;
11. Although the special high-voltage wire (HVx) provided with the instrument has been tested and qualified at the factory, it still needs to be kept away from the human body and the low-voltage test line (Cx) during measurement; neither the high-voltage core wire nor the high-voltage shielding wire is allowed to be grounded or connected to the low potential part of the test circuit.
The core wire and shielding wire of the CX input line are not allowed to contact the high-voltage part of the test circuit.
12. The instrument should be protected from moisture and severe vibration.
13. When the on-site interference is large and a definite result cannot be obtained with power frequency, the variable frequency measurement should be used; in other cases, power frequency measurement should be used.
14. After issuing the measurement command, if the measurement result does not appear on the screen for a long time (1 minute), it may be due to the test sample capacitance being too large or a crash; restart the machine and reduce the measurement voltage before measuring again.
15. If the test sample is short-circuited, measurement will not be possible, and the instrument will automatically protect. When a section extends from the paper outlet above the machine head, press the button once to stop paper feeding. The printing paper is allowed to be pulled outward.
Instrument Structure
Measurement circuit: all calculations such as Fourier transform, complex number operations, range switching, and variable frequency power supply control.
Control panel: printer, keyboard, display, and communication relay.
Variable frequency power supply: uses SPWM switching circuit to produce high-power sine wave stabilized output.
Step-up transformer: boosts the variable frequency power supply output to the measurement voltage, with maximum reactive power output of 2KVA/1 minute.
Standard capacitor: internal Cn, measurement reference.
Cn current detection: used to detect the current of the internal standard capacitor, 10μA～1A. Input resistance <2Ω.
Cx positive wiring current detection: only used for positive wiring measurement, 10μA～1A. Input resistance <2Ω.
Cx reverse wiring current detection: only used for reverse wiring measurement, 10μA～1A. Input resistance <2Ω.
Reverse wiring digital isolation communication: uses precision MPPM digital modem to convert the reverse wiring current signal.
