What is a Hipot Tester?

Hipot tester is a test instrument widely used in industry, aerospace, power and other fields, which can test the insulation performance of electrical or electronic equipment. It can simulate the effect of a high voltage charge on the equipment and is used to determine whether the equipment meets the relevant safety standards to ensure its safety performance under normal conditions of use. sisco shop for you to introduce more details.

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Operating Principle

The working principle of the Hipot tester is to apply a high voltage to the device to be tested through the test device and observe the change of its voltage resistance and leakage current. Specifically, it mainly includes the following two aspects:

• 1. High voltage source: The high voltage source is the core component of the withstand voltage tester, which provides high voltage power supply and generates the high voltage charge required by the device to be tested. The voltage and current are set according to the requirements of the device being tested. High voltage is usually applied to the input, output and housing of the device to be tested to detect whether there is leakage.
• 2. Test device: The test device consists of two main parts: a booster transformer and an ammeter.
  A booster transformer is a special type of transformer used to convert an ordinary voltage into a high voltage. The principle is to transform the low voltage current into the required high voltage current through an acceptable transformer ratio adjustment. A booster transformer usually contains multiple independent, isolated outputs that can provide a high-voltage charge to multiple devices at the same time.

Ammeter is used to measure the current of equipment under high voltage conditions. It is generally combined with a booster transformer to measure the leakage current of the device being tested. Ammeters usually operate in two modes: impedance mode and current mode. In impedance mode, the internal circuit of the ammeter generates an electric field identical to that of the voltage tester, which is used to detect the impedance of the device being tested. In current mode, the ammeter can directly measure the leakage current of the device under test

Key Features and Uses

• 1. High Voltage Testing: Hipot testers can generate high voltages, often exceeding the expected operating voltage of the equipment being tested. This high voltage is applied between the conductive parts of the device and its insulation to assess the quality of the insulation.
• 2. Insulation Resistance: One of the primary purposes of Hipot testing is to measure the insulation resistance of the device under test. Good insulation should have a high resistance, so a lower current reading on the tester indicates better insulation quality.
• 3. Leakage Current Measurement: Hipot testers measure the leakage current that flows through the insulation when the high voltage is applied. Elevated leakage current may suggest potential insulation issues or defects.
• 4. Pass/Fail Criteria: The test results are compared to predefined pass/fail criteria. If the leakage current remains within acceptable limits, the device passes the test. If the current exceeds these limits, the device is considered to have failed the Hipot test.
• 5. Safety Testing: In addition to assessing insulation, Hipot testing can also verify the safety of electrical equipment. It helps identify potential electrical hazards and can uncover issues that might lead to electrical shock or fires.
• 6. Types of Hipot Tests: There are typically two types of Hipot tests:
  Dielectric Withstand Test (AC Hipot): This test determines if the insulation can withstand high AC voltage levels for a specified duration.
  Insulation Resistance Test (DC Hipot): This test measures the insulation resistance by applying a high DC voltage.

Application

• 1. Electronics Manufacturing:
  Cable Assemblies: Hipot testing is used to verify the insulation of cable assemblies to ensure they meet safety and quality standards.
  Printed Circuit Boards (PCBs): PCBs and their components are tested to ensure that there are no electrical leakage paths or insulation breakdowns.
• 2. Medical Devices:
  Hipot testing is crucial for medical equipment to ensure patient safety and the integrity of the devices. Equipment such as medical grade power supplies, patient monitoring systems, and diagnostic devices undergo Hipot testing.
• 3. Aerospace and Avionics:
  Components and wiring in aircraft systems are subject to Hipot testing to guarantee reliable operation in demanding and safety-critical environments.
• 4. Power Distribution:
  Electrical power distribution systems, such as high-voltage cables and transformers, are tested to verify their insulation and overall integrity.
• 5. Consumer Electronics:
  Products like power adapters, chargers, and appliances are tested to ensure that they are electrically safe for consumers to use.
• 6. Automotive Industry:
  Vehicle components, such as electrical harnesses, connectors, and control modules, are subjected to Hipot testing to meet safety and reliability requirements.
• 7. HVAC and Industrial Equipment:
  Heating, ventilation, air conditioning (HVAC) systems and various industrial equipment may undergo Hipot testing to ensure safe and reliable operation.
• 8. Electrical Switchgear and Transformers:
  High-voltage equipment like switchgear and transformers are tested to verify their insulation properties and ensure they can handle high voltages safely.
• 9. Data Centers:
  Electrical systems and components in data centers are tested to guarantee continuous and reliable operation, as data centers are critical for businesses and organizations.
• 10. Lighting Systems:
  Lighting fixtures and systems are tested to ensure safety and insulation quality, especially for commercial and industrial applications.
• 11. Renewable Energy:
  Solar inverters, wind turbine components, and other renewable energy equipment are subjected to Hipot testing to verify their electrical safety and reliability.
• 12. Quality Control:
  In various manufacturing industries, Hipot testing is used as part of quality control processes to catch potential defects early in the production process.

The key goal of Hipot testing in these applications is to identify insulation issues, such as cracks, weak points, or inadequate insulation, before they lead to electrical breakdowns, fires, or safety hazards. It plays a vital role in ensuring that electrical and electronic products and systems meet safety standards and reliability requirements. sisco offers a variety of high-voltage testers for you to choose from, such as 100 kV 10 kVA AC DC Hipot Tester,100 kV 5 kVA AC DC Automatic Hipot Tester, and so on. If you are interested, please click to buy&#;

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Electrical safety is of utmost importance for all the electrical and electronic products. Today&#;s HIPOT (short for high-potential) testers&#;key test equipment for electrical safety&#;have come a long way in terms of features, programmability and safety involved in testing itself

SHWETA DHADIWAL BAID

JULY : Someone has rightly said that &#;Safety doesn&#;t happen by accident.&#; Today, most consumer electronics devices operate in close vicinity of the human body, be it a mobile , laptop, home appliance or medical device. Any product designed without electrical safety parameters in mind may result in a mishap. The finished product needs to be tested thoroughly before it is put in use. Several tests have to be conducted from design to production stage in order to ensure electrical safety of the component and the finished product.

No designer wants to design an unsafe product, but many a times the product may fail in operation due to some design flaw or faulty components. Electrical safety tests are performed on components such as transformers and switches, cables, motors and finished goods. Several standards organisations publish the permissible limit for different parameters. Organisations like CSA in Canada, UL/ETL in the United States, GS in Germany, EK in Korea, CCC in China and CNS in Taiwan provide electrical safety/international standards, shares Helena Wang, sales manager, GW Instek. In India, Indian Standards Institute (ISI) specifies electrical safety parameters for many products. Usually, manufacturers hire certified test labs to perform safety tests to comply with these standards and get their products certified.

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Insulation plays an important role in electrical safety. During production, most manufacturers include tests around insulation in order to meet safety requirements as per specific standards. As opposed to continuity tests that ensure current flow, there are tests performed using high potential (HIPOT) to ensure that the current does not flow from one point to another at a given voltage for a given time.

Need for electrical safety tests
Electrical safety tests may be mandated by the standards&#; organisations, but as a manufacturer, it is your social responsibility. Tests do consume some time in the production line, but these significantly reduce the risk of fires, accidents, electrical shocks, etc from the equipment. It is very important to test insulation as 80 per cent of electrical maintenance and testing involves evaluating insulation integrity.

Electrical insulation starts deteriorating in its performance as an insulator (extremely bad conductor) with time. The most important reason for testing insulation is to ensure public and personal safety. &#;Insulation testing is used to determine the integrity of windings or cables in motors, transformers switchgear and electrical installations,&#; shares Prachi Gupta, director, Avante Global. &#;By performing a high-potential test between de-energised current-carrying, grounded and grounding conductors, you can eliminate the possibility of having a life-threatening short-circuit or short-to-ground faults,&#; she adds.

Electrical and electronic systems when exposed to environmental factors such as dirt, grease, temperature, stress and vibration affect the dielectric material used in insulation. This may lead to insulation failure, resulting in loss of production or even fire. &#;It is important to identify the deterioration as early as possible to take corrective measures,&#; suggests Ms Wang.

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HIPOT tests
When a high potential is applied between isolated parts of a circuit or a product, the behaviour of electrical parameters helps identify broken or poor insulation, stray wire strands or braided shielding, spacing problem between terminals, tolerance errors, etc. This helps in making informed decision on the safety and quality of electrical circuits.

&#;The value/range of HIPOT depends on the device under test (DUT),&#; shares Rohit Manwani, chief executive officer of Sunil Associates. &#;Range of the instrument varies from industry to industry. Some industries can accept the sample if insulation resistance is more than mega-ohms, while some look for values in giga-ohms,&#; he adds.

High-potential tests can be divided into three distinct tests with different goals. To understand the high-voltage capacity of an insulating material, dielectric breakdown test is used. The voltage between the test points is increased continuously until the current increases suddenly. This is the point where insulation gets into conduction. Normally, this test is done during the product design and qualification stage.

[stextbox id=&#;info&#; caption=&#;Types of leakage currents&#;]

During the insulation test, a high voltage is generated that causes a small current (in micro-amperes) to flow through the conductor and insulation. The amount of current depends on the amount of voltage applied, the system&#;s capacitance, total resistance and temperature of the material. The value of insulation resistance read on the meter will be a function of following three independent sub-currents:

Conductive leakage current. Conductive current is a small current that normally flows through insulation, between conductors or from a conductor to ground. This current increases as insulation deteriorates and becomes predominant after the absorption current vanishes.

Capacitive charging leakage current. When two or more conductors are run together in a raceway, these act as a capacitor. Due to this capacitive effect, a leakage current flows through conductor insulation. This current lasts only a few seconds as the DC voltage is applied and drops out after the insulation has been charged to its full test voltage. In low-capacitance equipment, capacitive current is higher than conductive leakage current, but usually disappears by the time you start recording the data. Because of this, it is important to let the reading settle out before recording it. On the other hand, when testing high-capacitance equipment, the capacitive charging leakage current can last a very long time before settling out.

Polarisation absorption leakage current. Absorption current is caused by polarisation of molecules within the dielectric material. In low-capacitance equipment, current is high for the first few seconds and decreases slowly to nearly zero. When dealing with high-capacitance equipment or wet and contaminated insulation, there will be no decrease in the absorption current for a long time.

&#;Prachi Gupta, director, Avante Global

[/stextbox]

 [stextbox id=&#;info&#; caption=&#;Key safety points for test engineers&#;]1. Keep the unauthorised and unqualified persons away from the test area
2. Arrange the test bench and test procedure in orderly manner
3. Do not modify the test procedures without any knowledge
4. Make sure that custom test fixtures carry proper ratings and test equipment are correctly rated
5. Do not touch the DUT while the test is running
6. In case of a problem, first turn off/stop the test
7. Discharge the DUT completely in the DC test[/stextbox]
&#;Of course, the sample DUT that fails the test is rejected as it is completely damaged now,&#; shares Manwani. The dielectric withstand test is normally done at 75 per cent of the breakdown voltage. The test is performed to understand for how long the dielectric can withstand high voltage.

Insulation resistance (IR) test measures resistance of the insulating material. You apply a very high voltage across the dielectric, carefully measure the current and calculate the resistance using Ohms law. &#;For most of the products, the test is carried at 500V DC and the resistance should be at least 2 mega-ohms,&#; shares Ms Wang. &#;Usually IR is checked first, before putting the device for HIPOT test,&#; she adds.

Hipot testing can be carried by an AC or DC voltage. However, there are different considerations when using AC or DC voltages. The difference in the reading becomes significant when the DUT is highly capacitive. &#;AC voltage cannot charge a capacitive load, as reactive current flows instantly and remains consistent regardless of the time the voltage is applied. DC voltage will charge the capacitance of the DUT so you may see an inrush of current upon initial application of the voltage, but gradually the readings will dissipate as the DUT becomes charged. Normally, the relationship between AC and DC HIPOT tests is AC=1.414DC. For example, if you perform AC HIPOT test at a test voltage of 2 kV, then DC HiPOT test should be performed at 2.83 kV,&#; explains Ms Wang.

Expressing her views on the test methodology, Ms Gupta believes that the test method also depends on the type of the DUT. &#;For instance, when a low-capacitance equipment like electrical cabling or switchgear is tested, the time-dependent capacitive leakage and absorption leakage current become insignificant and decrease to zero almost instantly. This provides a perfect condition for accurate spot reading. On the other hand, when high-capacitance equipment such as long runs of cables,

large motors or generators are to be tested, the time-dependent current will last hours. This current will cause the meter reading to change constantly, making it impossible to obtain an accurate steady reading. This condition can be overcome by using a test that establishes a trend between readings, such as the step voltages or dielectric-absorption test. These tests do not depend on a single reading but on a collection of relative readings.&#;

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