Many kinds of inductor transformers are used in the ultrasonic power supply. These inductor transformers used in the ultrasonic power supply of Weihai national litre ultrasonic production are all treated with strict aging process, and few failures occur. But some manufacturers have a simple process, and these inductor transformers sometimes fail and the conventional detection method will occur. As follows:
1, the detection of color coded inductors put the multimeter in the R * 1 block, and the red and black pens are all connected to any lead of the color code inductor, when the pointer should swing to the right. According to the measured resistance value, the following three situations can be identified:
A, the measured color code inductor resistance value is zero, the internal short circuit fault;
The value of the DC resistance of the B and the measured color code inductor is directly related to the coil diameter and the number of winding loops used to coil the inductor coil. As long as the resistance value can be measured, the measured color code inductor is normal.
2, the detection of the transformer in the middle and the week:
A, allocating the multimeter to the R x 1 gear, according to the rules of each winding pin of the transformer in the middle and the week, check the connection of each winding one by one, and then judge whether it is normal or not.
B, test insulation performance of the multimeter placed in the R x 10K gear, do the following state tests: (1) the resistance between primary and secondary windings; (2) resistance between primary winding and shell; (3) resistance between secondary windings and outer shells. The above test results are divided into three cases: (1) the obstruction is infinite: normal; (2) the resistance is zero: there is a short circuit fault; (3) the resistance is less than infinity, but more than zero: there is a leakage fault.
3. Detection of ultrasonic power transformer:
A, by observing the appearance of the transformer to check whether there are obvious anomalies. If the coil lead is broken, off - welding, whether the insulation material has burnt trace, whether the fastening screw of the iron core has loosened, the silicon steel sheet has rust, and whether the winding coil is exposed or not.
B, insulation test: use the multimeter R x 10K to measure the resistance value between the core and the primary, the primary and the secondary, the core and the secondary, the electrostatic shielding layer and the secondary and secondary windings, and the multimeter pointer should not be moved at infinity. Otherwise, it shows that the insulation performance of the transformer is bad.
C, coil on-off detection: put the multimeter in R * 1 block test, if the value of a winding is infinity, it shows that the windings have circuit breakdowns.
D, discriminant initial and secondary coils: the primary and secondary pins of the power transformer are usually extracted from both sides, and the primary windings are mostly marked with 220V, and the secondary windings are marked with the rated voltage, such as 15V, 24V, 35V and so on. Then they are identified by these markers.
E, detection of no-load current: (a) direct measurement. All the secondary windings are all opened, and the multimeter is placed in an alternating current block (500mA), which is connected to the primary winding. When the plug of the primary winding is inserted into 220V AC power, the no-load current value is indicated by the multimeter. This value should not exceed 10% to 20% of the full load current of the transformer. The normal no-load current of power transformers in common electronic equipment should be around 100mA. If it goes too far, it indicates that the transformer is short circuited. (b) indirect measurement method. In the primary winding of the transformer, a 10/5W resistor is connected in series, and the secondary parts are still empty. Dial the multimeter to the AC voltage gear. After power, voltage resistance R measured at both ends of two pen down U, and then calculate the no-load current by Ohm's law I I =U/R is empty, empty;
Detection of F, no-load voltage: the primary connection of the power transformer to the 220V city electricity and the AC voltage connection of the multimeter to measure the no-load voltage values of each winding (U21, U22, U23 and U24) should conform to the required values. The allowable error range is generally: the high voltage winding is less than + 10%, the low voltage winding is less than + 5%, and the two groups of symmetrical windings with the center tap The voltage difference should be less than 2%;
The temperature rise of the G and the general small power transformer is 40 ~ 50 degrees. If the insulation material is better, the temperature rise can be increased.
H, detection and discrimination of the same end of the windings: in the use of power transformers, sometimes in order to get the required secondary voltage, two or more secondary windings can be used in series. When the power transformer is used in series connection, the same name ends of the winding in series must be connected correctly. Otherwise, the transformer can not work properly.
The comprehensive detection and discrimination of short circuit faults of I and power transformers: the main symptoms of a power transformer after a short circuit fault are the severe fever and the output voltage disorder of the secondary winding. Usually, the more the interturn short-circuit point is, the larger the short circuit current will be, and the more serious the transformer will be. A simple way to detect whether there is a short-circuit fault in the power transformer is to measure the no-load current. The transformer with short circuit faults will be far less than the 10% of full load current. When the short circuit is serious, the transformer will rapidly generate heat within tens of seconds after the load is added to the load. At this time, no load current can be measured, and it is concluded that there is a short-circuit point in the transformer.
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