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Detection of switching power supply transformer

In Electronic Infomation Category: D | on April 12,2011


1, by observing the appearance of the transformer to check for any obvious anomalies. If the coil wire is broken, loose weld, insulation materials have burnt marks, whether core fastening screw loose, silicon steel sheet without rust, if exposed coil winding and BAS21LT1G datasheet and so on.

2, insulation resistance testing. R 10k block with a multimeter measured the core and BAS21LT1G price and primary, primary and BAS21LT1G suppliers and the secondary, the core and the secondary, the secondary electrostatic shield and panties, the secondary resistance between the windings, multimeter pointer should not refer to the location in the infinite action. Otherwise, the transformer insulation that bad.

3, the coil off of the test. Placed in the multimeter R 1 block, test, if a winding resistance value infinite, then there is this winding circuit failure.

4, early identification, secondary coil. Power transformer primary and secondary pin pin respectively, from both sides of the leads are generally, and more marked with the 220V primary winding of the words, the secondary winding is marked rated voltage value, such as 15V, 24V, 35V and so on. Identification based on these markers.

5, no-load current detection.

A, direct measurement method. All the secondary windings will be all open, the AC current meter placed in block (500mA, the primary winding in series. When the primary winding of the plug into 220V AC power, the meter is indicated by the load current value. This value should not be transformer full load current is greater than 10% to 20%. The most commonly normal electronic equipment power transformer load current should be 100mA or so. If the outside too much, then the transformer short-circuit failure.

B, indirect measurement method. Transformer primary winding in series with a 10 / 5W resistor, the secondary is still all empty. AC voltage meter to the block allocation. Power, the use of two tables pen measured voltage drop across the resistor R U, and then use Ohms law calculate the load current I empty, that I empty = U / R. F circuit voltage detection. The power transformer primary connection 220V electricity, then followed with a multimeter measuring AC voltage of each winding no-load voltage (U21, U22, U23, U24) should meet the requirements of value, is generally permissible error range: 10 HV Winding %, low-voltage winding 5%, with a center-tapped windings of the voltage difference between the two groups should be symmetrical 2%.

6, generally allow low-power power transformer temperature rise of 40 ~ 50 , if the quality is better insulating materials, allowing the temperature rise can be improved.

7, detection of the same name each winding end discrimination. When using the power transformer, sometimes in order to obtain the required secondary voltage can be two or more secondary windings connected in series to use. Used in series with the power transformer, to participate in series of the same name each winding terminal must be properly connected, can not be wrong. Otherwise, the transformer does not work.

8, power transformer short-circuit failure of the comprehensive test discrimination. Power transformer short-circuit failure occurred after the main symptoms are fever and severe disorders secondary winding output voltage. Typically, the coil inter-turn short circuit within the more points the greater the short-circuit current, while the more serious heat transformer. Power transformer testing to determine whether there is an easy way to short-circuit failure is to measure the load current (test method described earlier). Transformer short-circuit fault exists, the no-load current value can be much larger than the full load current of 10%. When short-circuit serious, no-load power transformer within tens of seconds after the rapid heating will be, hand-to-core will be hot feeling. At this point do not measure the load current transformer can be concluded that short circuit exists.

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