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Miten valita sopiva säädettävä teholähde?
Käyttökohde ratkaisee, joten tarvitaan yleensä ainakin seuraavat tiedot käyttötarpeesta:
  • Halutaanko teholähteestä ulos vaihto- vai tasasähköä tai molempia yhtäaikaa eli AC, DC, AC+DC?
  • Tiedettävä tarvittava max. jännite/virta/teho . Teholähteen hinta, paino ja koko yleensä nousee kokonaistehon kasvaessa (ylimitoitus ei kannata).
  • Asennetaanko teholähde työpöydälle vai laitetelineeseen (räkki)? Tarvitaanko lähtöliitännät teholähteen edestä vai takaa /molemmat?
  • Tapahtuuko laitteen säätö/ohjaus laitteesta käsin vai välän kautta (PC/PLC) ? Jos väylän kautta niin minkä: GPIB/LAN/USB/RS-232/ jne.
  • Halutaanko teholähteeltä muita ominaisuuksia: Esim. se toimii myös kuormana eli vastaanottaa virtaa tai tuottaa myös negatiivista jännitettä?
Huomatkaa, että maahantuomme usean eri valmistajalta teholähteitä, jotta jokaiseen käyttökohteeseen löytyisi paras/taloudellisin vaihtoehto. Ottakaa yhteyttä niin autamme Teitä myös mielellämme teholähteen valinnassa.
What is the difference between an insulation resistance test and a Hipot test?
An insulation resistance test is similar to a Hipot test in that its purpose is to verify that the product meets the requirements for protection against electric shock and fire as well as to check the functionality or performance of the insulation system. The two tests are different, however, the Hipot test detects an insulation defect by checking whether no dielectric breakdown occurs while the insulation resistance test does so by measuring resistance. The test method is to apply a DC voltage of a specified magnitude, typically 5 to 10 times greater than the voltage that the product normally handles, for a specified duration of time after moisture absorption (which may be omitted in some cases). If proven to have sufficiently large resistance the product is considered to meet the requirements for protection against electric shock and fire. Many safety standards regard the insulation resistance test as part of the type inspection and state that it may be omitted from the 100 percent inspection on the production line.
Why is a Hipot test necessary?
All electrical products should be safe to use. Under no circumstances should they put users’ lives at risk nor damage their assets. That is why we have safety standards both at home and abroad. A Hipot test is intended to verify that no dielectric breakdown will occur in a product; in other words the test is necessary to ensure that the product under test is safe to use. For this reason every manufacturer of electrical products is obliged to perform a Hipot test as part of their inspection process regardless of whether they have an intention to comply with specific safety standards. Ensure that the product under test is safe to use. For this reason every manufacturer of electrical products is obliged to perform a Hipot test as part of their inspection process regardless of whether they have an intention to comply with specific safety standards.
Do I need to use a Hipot tester to perform a Hipot test?
Every safety standard specifies the requirements (method) for a Hipot test. (Some standards may include requirements regarding a tester to be used.) Therefore as long as you can perform a Hipot test in a way that meets all specified requirements you do not necessarily need to use a Hipot tester. One thing to note, however, is that a Hipot tester is specifically designed to ensure the safety of the operator during the course of a Hipot test. We therefore recommend using a Hipot tester where possible. For example Electrical Appliance and Material Safety Law (in Japan) specifies that the dielectric strength testing facilities for home electrical appliances such as washing machines, refrigerators and television sets shall:

(1) Be equipped with a transformer, voltage regulator, and voltmeter (with accuracy of class 1.5 or above) or a dielectric strength tester with such devices built into it.
(2) Have the ability to adjust the secondary voltage easily and smoothly to the dielectric strength test voltage.

As suggested by this law the use of a Hipot tester is not necessarily required.
If a Hipot tester capable of DC output is available how do I use the DC Hipottester and an AC Hipot tester?
A Hipot test is basically performed with an AC voltage. In some cases, however, AC Hipot testing may cause a large current to flow to the noise filter or other capacitive component adversely affecting the test. Some safety standards permit DC Hipot testing to be conducted in place of AC Hipot testing where appropriate. Many of such standards specify that the DC test voltage should be equal to the peak value of the specified AC test voltage. Note that some safety standards require that DC Hipot testing be performed when testing a DC circuit.
Why is a DC voltage used for an insulation resistance test?
An insulation resistance test detects an insulation defect by measuring the resistance of the device under test. A DC voltage is used because it is more convenient for measuring only the resistance component.
Due to poor (commercial) power supply conditions in my workplace the Hipot tester outputs distorted waveforms. What do the typical standards say about waveform skew?
Most safety standards specify that the test voltage waveform should be a ”sine waveform.” It is generally said that sinusoidal waves having a distortion factor not greater than 5% may be called sine waveforms. Also, some safety standards (e.g., UL1492 ”Audio-Video Products and Accessories”) define the requirements regarding the test waveform as follows: ”The test waveform shall be a sine waveform within the frequency range between 40 and 70 Hz and its peak value shall be at least 1.3 times but not greater than 1.5 times its RMS value.”
Can I perform a Hipot test for a three-phase AC device without using a three-phase AC power supply?
It is not necessary to use a three-phase AC power supply. The Hipot test is intended to verify that those conductive parts that can potentially come into contact with the human body are fully insulated from the live parts. Therefore the test is conducted between the primary power line and the conductive parts that may come into direct contact regardless of the structure of the device under test.
At my workplace a Hipot test is performed by applying a 1200-volt voltage for one second, instead of a 1000-volt voltage for one minute for the benefit of improved productivity. Is this a proper way to conduct a Hipot test?
Some standards permit the production line Hipot testing to be conducted in the manner described above. So your idea is not off the mark. Generally a Hipot test checks that no dielectric breakdown occurs by applying a specified voltage for a specified duration of time. This is possible because degradation in the insulating material can be treated as functions of voltage and time. In some cases the safety standard may allow a Hipot test to be performed by applying a higher voltage for a shorter duration of time. For example a number of safety standards state that the duration of a production line Hipot test may be reduced to one second in order to improve productivity on condition that a voltage as high as 6/5 the voltage specified for the one-minute test is applied. Note, however, that the actual requirements may differ for various safety standards: it is necessary to check the standard concerned to make sure.
Is there any rule regarding the order of performing a Hipot test and aninsulation resistance test?
Some safety standards stipulate that a Hipot test and an insulation resistance test should be conducted in a specified order. Where such an order is defined an insulation resistance test often tends to be performed first. Some standards do not require an insulation resistance test.
What is a leakage current?
Generally, a current flow that is induced when a voltage is applied to an insulating material (insulator) is called a leakage current. Therefore any currents that flow through the insulator during a Hipot test, insulation resistance test or line leakage current test are all referred to as leakage currents. However, the international standard IEC60990:1999-08 for leakage current measurement methods does not use the term ”leakage current.” Instead it uses the terms ”touch current” and ”protective conductor current.” So the formal name of the standard is ”Methods of measurement of touch current and protective conductor current.” In any of these tests the insulator is considered to be of poor performance if a leakage current flows through it. Naturally the higher the leakage current is the greater the risk of electric shock or fire becomes.
The Hipot tester I use has a label attached on it showing when it was last calibrated. What is calibration?
Calibration is to compare the indicated value on a measuring instrument against the true value. A measuring instrument serves its purpose only if it produces an accurate reading. One familiar example is a weighing scale. The act of determining the value to be given to a measuring instrument is referred to as calibration. Every electrical measuring instrument has error. The instrument needs to be adjusted if its indicated value is outside the margin of error defined in its specification. Generally the whole process including this adjustment is sometimes called calibration. If you send in a measuring instrument for us to calibrate we will adjust the instrument so that it operates within its specification and return the calibrated instrument to you along with its calibration data (test sheet) with a ”calibration label” showing the date of calibration attached on the instrument. There is no specific rule as to how often to calibrate a measuring instrument. Customers who ask us to perform calibration for them typically want to have their instruments calibrated at intervals of six or 12 months.



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