Inductors, transformers detection methods and experience 1 color code inductor test Multimeter placed R × 1 block, red, black pen each pick color code inductors any leads, then the pointer should be to the right swing. According to the measured resistance value, can be divided into the following three cases to identify: A measured color code inductor resistance is zero, its internal short-circuit fault. B. The size of the DC resistance of the color code inductor under test is directly related to the diameter of the enameled wire used for winding the inductor coil and the number of turns. As long as the resistance value can be measured, it can be considered that the color code inductor under test is normal . For more information, please visit the website 2 weeks in the transformer testing A dial meter to R × 1 block, in accordance with the weekly transformer winding pin arrangement of the law, one by one to check the continuity of the winding situation, and then determine whether it is normal. B Insulation Check the multimeter placed R × 10k block, do the following several state test: (1) the resistance between the primary winding and the secondary winding; (2) the resistance between the primary winding and the shell; (3) The resistance between the secondary winding and the case. The test results appear in three cases: (1) resistance is infinite: normal; (2) resistance is zero: a short circuit fault; (3) resistance is less than infinity, but greater than zero: a leakage fault. 3 power transformer testing A by observing the appearance of the transformer to check whether there is any obvious abnormalities. Such as the coil lead is broken, desoldering, insulating material whether there are traces of burning, iron core fastening screw loose, silicon steel rust, winding coil is exposed or not. B insulation test. With multimeter R × 10k block were measured iron core and primary, primary and secondary, core and the secondary, electrostatic shielding layer and the secondary and secondary winding resistance between the secondary, multimeter pointer should mean that in the infinite position is not move. Otherwise, indicating transformer insulation performance is not good. C coil off detection. The multimeter placed R × 1 block, the test, if the resistance of a winding is infinite, then the winding has an open circuit fault. D determine the primary and secondary coils. The primary and secondary pins of the power transformer are generally drawn from both sides respectively, and the primary winding is marked with 220V words, while the secondary winding is marked with the rated voltage value, such as 15V, 24V, 35V and so on. According to these marks to identify. E no-load current detection. (a) Direct measurement. All the secondary windings are fully open, the multimeter placed in the AC current block (500mA, string into the primary winding. When the primary winding plug into the 220V AC mains, the meter indicates the no-load current value. Greater than the transformer full load current of 10% to 20%. General common electronic equipment power transformer normal load current should be about 100mA. If too much, then the transformer short-circuit fault. (b) Indirect measurement. In the primary winding of the transformer in series with a 10 / 5W resistor, the secondary is still empty. Put the multimeter to AC voltage block. After the power is turned on, measure the voltage drop U across the resistor R with two test leads and then calculate the no-load current I null using Ohm's law, that is, I null = U / R. F no-load voltage detection. The power transformer primary access 220V mains, AC voltage with a multimeter then measured the value of each winding no-load voltage (U21, U22, U23, U24) should meet the requirements, the allowable error range is generally: high voltage winding ≤ ± 10 %, Low voltage winding ≤ ± 5%, voltage difference between two symmetrical windings with center tap should be ≤ ± 2%. G General low-power power transformer allows temperature rise of 40 ℃ ~ 50 ℃, if the insulation material used is better quality, allowing temperature rise can be increased. For more information, please visit the website H test to determine the winding end of the same name. In the use of power transformers, sometimes in order to obtain the required secondary voltage, two or more secondary windings can be used in series. The use of tandem method using the power transformer, to join the series of the windings of the same name side must be properly connected, can not make a mistake. Otherwise, the transformer can not work normally. I. Power Transformer short-circuit fault comprehensive detection of discrimination. Power transformer short-circuit fault occurs after the main symptoms are serious heat and secondary winding output voltage anomalies. In general, the more inter-turn short-circuit points in the coil, the greater the short-circuit current, and the more severe the transformer heats up. The simple way to test to determine if a power transformer has a short-circuit fault is to measure the no-load current (the test method is described earlier). In the case of transformers with short-circuit faults, the no-load current will be much larger than 10% of the full load current. When the short circuit is serious, the transformer will rapidly heat within tens of seconds after the no-load power is turned on. There will be a feeling of hotness when touching the iron core by hand. At this time without measuring the no-load current can be concluded that the transformer short-circuit point exists. Second, the detection methods and experience of transistors and transistor triode evaluation formula 1, diode detection methods and experience 1 detection of low-power crystal diode A judge positive and negative electrodes (a) Observe the symbol markings on the housing. The diode's housing is usually marked with a diode symbol, with a triangular arrow at one end for the positive and negative on the other end. (b) Observe the color point on the housing. At the point
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