A VLF AC Hipot Tester is an important tool for testing the insulation performance of capacitive equipment like power cables and rotating motors. It combines precision electronic circuits with high-voltage generation units. Therefore, correct daily maintenance and storage are crucial for ensuring test accuracy, equipment longevity, and operational safety.
Here are the daily maintenance and storage guidelines for a VLF AC Hipot Tester, divided into two main parts: "Daily Maintenance" and "Proper Storage".
I. Daily Maintenance
Maintenance should follow the principle of "Inspect before testing, monitor during testing, and reset after testing."
1. Pre-Test Inspection
Visual Inspection: Before each use, carefully check the main unit, high-voltage connection cables, ground wire, output terminals, etc., for obvious physical damage such as cracks, breaks, or deformation. Pay special attention to the insulation layers of the high-voltage output terminals and cables, ensuring no cracking or exposed copper.
Cleaning and Dust Removal: Use a dry, soft cloth to gently wipe dust and oil stains from the equipment surface and insulating components. It is strictly forbidden to use organic solvents like alcohol, acetone, or wet cloths for cleaning, especially on the LCD screen and high-voltage components, to avoid damaging insulation or surfaces.
Power and Grounding Check: Confirm that the power supply voltage is within the allowed range (e.g., AC 220V ±10%). It is essential to ensure the equipment's grounding terminal is reliably connected to earth ground; this is the primary safety measure.
Connection Check: Inspect all plugs, sockets, and knobs for integrity and ensure connections are secure to prevent arcing or test interruptions due to poor contact.
2. Monitoring During Testing
Immediate Shutdown for Abnormalities: During testing, closely monitor the equipment's operating status. If any of the following abnormalities are observed, immediately cut off the high voltage and stop for inspection:
Unusual sounds from the equipment (e.g., discharge sounds, cracking).
Smelling burning or overheating insulation.
Abnormal jumping or instability of the LCD display data.
Activation of protection indicators (e.g., overvoltage, overcurrent).
Environmental Monitoring: Ensure the test environment meets requirements (typically, no strong electromagnetic interference, relative humidity <80%, temperature between -10°C and 40°C). Avoid outdoor testing in severe weather conditions (e.g., thunderstorms, high humidity).
3. Post-Test Procedures
Complete Discharge: After the test concludes, be sure to fully discharge the test object and the high-voltage output terminal using the dedicated discharge rod provided with the equipment before disconnecting any connections. This is a critical step to prevent electric shock from residual high voltage.
Reset and Shutdown: Turn the output voltage adjustment knob counterclockwise to zero, then turn off the equipment's power switch, and finally disconnect the main power supply.
Cable Management: Gently coil the high-voltage and power cables, avoiding sharp kinks or tight bends that could break internal wires.
II. Proper Storage
Good storage practices significantly extend the equipment's service life.
1. Storage Environment
Moisture Prevention: The equipment must be stored indoors in a dry, well-ventilated area. The ideal ambient humidity is around 60%, not exceeding 80% maximum. Moisture is a primary cause of internal component oxidation and insulation degradation. Using a dehumidifier or desiccant is recommended.
Suitable Temperature: The storage environment temperature should be between -20°C and 60°C (refer to the manufacturer's manual), avoiding direct sunlight and proximity to heat sources (e.g., radiators, stoves).
Avoid Corrosive Substances: Ensure the ambient air is free of acid, alkali, or other corrosive gases or dust, which can corrode circuit boards and metal connectors.
Shock and Dust Protection: Place the equipment on a stable bench or inside a cabinet, avoiding severe vibration and impact. When not used for extended periods, cover it with a dedicated dust cover.
2. Periodic Maintenance (For infrequently used equipment)
Regular Power-On: If the equipment is not used for an extended period (e.g., over one month), it is advised to power it on for at least half an hour at least once a month. Powering it on helps drive away moisture using the device's own heat and keeps internal components like capacitors active. This can be done without any load connected, just by turning the unit on.
Functional Check: Perform a basic functional check, such as a no-load voltage rise test, every six months or yearly to ensure normal performance.
Regular Calibration: As a measuring instrument, the accuracy of the VLF generator's output voltage and frequency is crucial. It should be sent to a qualified metrology department for regular calibration according to the manufacturer's recommendation or metrology regulations (typically once a year) to ensure the accuracy and reliability of test data.