The basic hipot test applies a high voltage from the conductors to the chassis of the device-under-test DUT. Its purpose is to confirm that the insulation and isolation of the non-conducting surfaces from the operating voltage is sufficient to avoid a shock hazard. Both AC and DC hipot tests are possible and, in general, the test should use the same type of voltage as it would be during normal operation.
However, if a DC hipot test is used on an AC circuit, the hipot voltage should be two times the peak 2 x 1. Four double-insulated products, higher voltages will often be specified in the test standard. In addition, this class of device typically requires special fixturing to connect the non-conductive outer shell to a conductive element.
Defects that are often detected with the hipot test include contamination dirt, debris and lack of proper spacing creepage and clearance of components. Creepage is measured across surfaces, clearance is the air gap between components. Contamination would likely cause an unacceptable level of leakage current.
Clearance problems could result in breakdown. Desirable Dielectric Withstand Test Features. Adjustable maximum output voltage. Insulation Resistance.
Insulation resistance testing is likely to be required in motor winding, transformer winding and other applications involving cabling or insulated wire. Insulation resistance testing typically involves confirming that the resistance exceeds a defined high resistance value.
In many instances, insulation resistance needs to be measured between several conductors. To make this measurement, all the conductors except one are shorted together and the test voltage is applied from the remaining conductor across the bundled ones. Each wire is then, in turn, tested in this fashion. Desirable Insulation Resistance Test Features. Ground Continuity. Ground continuity testing is performed to confirm that the conductive chassis of a device is safely connected to the earth ground pin on the power plug.
This assures protection against shock hazards even if the equipment suffers an internal short to the chassis. The current would be shunted via the ground wire and would likely trip the breaker or blow the fuse. Ground continuity is performed by applying a low current e. Desirable ground continuity features include:. With its 4-foot leads, the accessory offers easy hipot and continuity test connection of corded products.
Where ground continuity measures the resistance of the safety ground connection, the ground bond test assures the integrity of the connection. Using the same test setup a high current is passed through the circuit. If the ground bond is solid, the current passes without a change in resistance.
If weak, the resistive heating of the current would induce a failure of the bond. Desirable Ground Bond Test Features. Part 1 of this white paper discussed the functions and features of these high-performance instruments.
The purpose of this section is to guide the hipot test user through the steps needed to make sure testing is done safely since potentially lethal voltages and currents are involved in the testing process. Hipot Test Station Set-Up. Because there is no substitute for operator competence, the importance of having trained personnel as the first step to a safe testing environment cant be overstated.
The operator should be in good health, operators with special medical conditions should not work with high voltage. All operators should understand that high voltage is dangerous, and care must be taken to avoid contact with energized circuits.
They should have knowledge of the effects of electrical currents on the human body and how best to avoid shock hazards.
Operators should also be taught compression-only CPR. Operators must understand the workings and importance of safety interlocks and why the interlocks should never be disabled. They must also understand the hazards of wearing metallic jewelry around electrical equipment and show how to interrupt power quickly in emergency situations. Other operator requirements include programming the necessary tests and storing them in memory. Download as PDF. Still need help? Ask us. Stay in the know.
Sign up to our mailing list today to stay up to date with the latest industry news and information from Seaward. Sign Up. Sign up to our Newsletter. I'd like to talk to a sales advisor Our team of sales advisors are on hand to help you with any queries you have about our products. Request a call back. Request a quote. Contact us Email: sales seaward. Hipot testing can also be done on production lines during the manufacturing process.
Testing is designed to detect whether the assembly of a production unit is the same as those units that were subjected to type testing.
Potential issues inadvertently introduced or applied during manufacturing like creepage or improper clearance distances, a pinhole defect in insulation, and locating an enlarged solder footprint can be identified. A Hipot test is necessary to test the stress of an electronic device for safety and quality purposes.
Under high voltage it checks that there is no breakdown or perforation occurring, and that insulation distances on the line and in the air are respected. Tests can be conducted between mutually insulated sections of a part or energized parts and electrical ground. In either case, during testing, electric current will flow between two points. Typically, the test works by connecting one end of the supply to the ground and the other end to the conductor undergoing testing.
When you apply an AC voltage, the current that flows is equal to the voltage divided by the impedance. The impedance, however, is complex because it contains both resistive real and capacitive reactive components.
Because these two components of AC current are out of phase with each other, they combine in a complex manner to form the total current, as shown in Figure 6. The tester must therefore be very sensitive to detect a change in total current in a DUT with high capacitance. AC testing at high voltage levels may also degrade some types of insulation. To avoid such problems, most manufacturers try not to exceed the required voltage levels and hold times, and to minimize the number of tests performed on a given product.
A typical DC hipot test applies a voltage in gradual steps, commonly called ramping, pausing after each increase to allow the capacitance of the DUT to absorb a charge and stabilize. As shown in Figure 8, the current increases sharply after each increase in voltage as the capacitance charges, and then decreases to a low steady-state value.
The time required for the charging current to decay after each step is called the stabilization time. Current that flows after the stabilization time has passed represents the leakage current through the insulation. If the voltage steps are too large, the sharp rise in charging current when the step is applied may exceed the high current limit, causing the test to fail prematurely.
The magnitude and timing of the steps, therefore, should be carefully matched to the characteristics of the DUT. By monitoring current flow as you gradually increase the applied voltage, waiting for the charging current to decay, and observing the leakage current if any , you can detect a potential insulation breakdown before it occurs.
If the leakage current suddenly starts to increase over the expected value, an insulation breakdown is likely to occur soon. Interrupting the test at this point can save the insulation from breakdown. The test fails but the product is not damaged and may be salvaged by visual inspection or some other means. If the product being tested does not have significant capacitance, there is little or no charging current, and the rate at which the voltage is gradually increased can be much more rapid.
Because a DC hipot test charges the capacitance of a DUT, the charge itself can present a hazard to testing personnel that must be removed after the test is over. Remove the stored capacitance by discharging the DUT to ground. Typically, the hipot tester automatically discharges the DUT for the same period of time the test voltage was applied.
If it does start to occur, the insulation is about to fail. A good tester, therefore, should detect presence of any arcing before real damage occurs.
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