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Transformer Detection Method And Experience Nov 01, 2017

1, color code inductor detection

Will be placed in the R × 1 block, red, black pen each color code inductor any of the lead-out, then the pointer should swing to the right. According to the measured value of the 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, measured color code inductor DC resistance value and wound inductor coil used in the enamel wire diameter, the number of turns around the circle has a direct relationship, as long as the resistance can be measured, you can think that the measured color sensor is normal of.

2, in the week of the transformer detection

A, the multimeter to R × 1 block, according to the transformer in the winding of each winding rules, one by one check the winding off the situation, and then determine whether it is normal.

B, the detection of insulation performance will be placed in the R × 10k block, do the following several state tests:

(1) the resistance between the primary winding and the secondary winding;

(2) the resistance between the primary winding and the housing;

(3) the resistance between the secondary winding and the housing.

The test results are divided into three cases:

(1) the 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, the power transformer detection

A, by observing the appearance of the transformer to check whether there are obvious abnormalities. Such as whether the coil lead broken, desoldering, insulation materials are scorched traces, the core tightening screw is loose, silicon steel sheet with or without corrosion, winding coil is exposed and so on.

B, insulation test. With a multimeter R × 10k block were measured core and primary, primary and secondary, core and the sub-level, electrostatic shielding and pantal secondary, secondary resistance between the windings, multimeter pointer should be in the infinite position is not move. Otherwise, the transformer insulation performance is poor.

C, coil on and off detection. The multimeter placed in the R × 1 block, the test, if the resistance of a winding is infinite, then this winding has a road fault.

D, identify the primary and secondary coils. Power transformer primary and secondary pins are generally drawn from both sides, and the primary winding with more than 220V words, the secondary winding is marked rated voltage, such as 15V, 24V, 35V and so on. And then according to these markers to identify.

E, no-load current detection. (a)  direct measurement method. All the secondary winding all 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 multimeter is indicated that no-load current value. More than 10% to 20% of the full load current of the transformer. General common electronic equipment Power transformer normal no-load current should be about 100mA. If too much, then the transformer has a short circuit fault. (B)  indirect measurement method. Of the primary winding in series with a 10 / 5W resistance, the secondary still all the no-load. The multimeter dial to the AC voltage block. After power, with two test leads R measured resistance R across the voltage drop U, and then calculated by Ohm's law Load current I, ie I = U / R.

F, no-load voltage detection. (U21, U22, U23, U24) should meet the required value, the allowable error range is generally: high voltage winding ≤ ± 10 (U21, U22, U23, U24) should meet the requirements of the value, the allowable error range is generally: high voltage winding ≤ ± 10 %, Low voltage winding ≤ ± 5%, with the center of the two groups of symmetrical winding voltage difference should be ≤ ± 2%.

G, the general low-power power transformer to allow the temperature rise of 40 ℃ ~ 50 ℃, if the quality of insulating materials used to allow the temperature rise can also be improved.

H, detection of the same name to identify the winding side. When using a power transformer, sometimes in order to obtain the desired secondary voltage, two or more secondary windings can be used in series. When using the power transformer in series method, the same terminal of the winding in series must be connected correctly and can not be mistaken. Otherwise, the transformer does not work properly.

I, power transformer short circuit fault detection of comprehensive detection. Power transformer short circuit after the failure of the main symptoms are serious fever and secondary winding output voltage disorders. Often, the more the short-circuit point between the turns of the coil, the greater the short-circuit current, and the more severe the transformer heat. A simple way to determine whether a power transformer has a short circuit fault is to measure no-load current (the test method has already been described earlier). There is a short circuit fault of the transformer, the no-load current value will be much greater than 10% of full load current. When the short circuit is serious, the transformer in the no-load power within tens of seconds after the rapid heat, hand touch the heart will have a hot feeling. At this point do not measure the no-load current can be determined that there is a short circuit point.

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