1, color-coded inductors detection
The multimeter on the R × 1 block, red, black table pen then color code the inductor any terminations, the pointer should be the right swing. According to the size of the measured resistance value points to identify the following three conditions:
A, the measured color-coded inductor resistance value is zero, the internal short circuit faults.
, The inductor DC resistance of the measured color code the size of the wound inductor coil used enameled wire diameter, the number of laps around the system has a direct relationship, as long as we can measure the resistance value can be measured color-coded inductors normal the.
2 weeks transformer testing
A, multimeter dial to the R × 1 block, the pinout law in accordance with the winding of the transformer in the week, check the winding off one by one, and then determine whether the normal.
B, detection of insulation performance multimeter placed on R × 10k block, several states tests are as follows:
(1) between the primary windi ng and secondary winding resistance value;
(2) the resistance value between the primary winding and shell;
(3) the resistance value between the secondary winding and shell.
The above test results divided into three cases:
(1) the resistance is infinite: normal;
(2) the resistance is zero: there is a short circuit fault;
(3) the resistance is less than infinity, but greater than zero: leakage faults.
3, the detection of power transformer
A, by observing the appearance of the transformer to check whether there are obvious anomalies. Such as the coil wire is broken, sealing off the insulating material is burnt traces, core fastening screw loose, silicon steel sheet with or without corrosion, the windings have exposed.
B, the insulation test. With a multimeter R × 10k block were used to measure the core and primary, primary and all secondary, core and sub-electrostatic shield and panties secondary, secondary inter-winding resistance value, the meter pointer should be the infinity position activities. Otherwise, the description of the transformer insulation performance is bad.
C, coil break detection. Multimeter in the R × 1 block, the test, a winding resistance is infinite, then this winding open circuit failure.
D, to distinguish primary and secondary windings. The power transformer prim ary pin and secondary pins are generally leads from both sides, and the primary winding 220V words, the secondary winding is marked on the value of the rated voltage, 15V, 24V, 35V. Based on these markers to identify.
E-load current detection. (A) The the î€ direct measurement method. Will all of the secondary winding is all open, the multimeter in AC current block (500mA in series with the primary winding when the primary winding of the plug into the 220V AC mains, multimeter instructions is to no-load current value. This value should not transformer full load current of 10% to 20% greater than normal common electronic equipment power transformer no-load current should be about 100mA. if exceeded too much, then the transformer short-circuit failure. (b) the the î€ indirect measurement method. a 10/5W resistor in series in the primary winding of the transformer secondary is still all no-load. to dial the multimeter to the AC voltage block. power, with two tables docum ent measuring the voltage drop across the resistance R U-, and then use Ohm\\ s law to calculate no-load current I empty, empty I = U / R.
F, no-load voltage detection. The primary access of the power transformer 220V mains AC voltage with a multimeter, then turn measured no-load voltage of each winding (U21, U22, U23, U24) shall comply with the required value, the allowable error range is generally as follows: high voltage winding ≤ ± 10 %, the low voltage winding ≤ ± 5%, two sets of symmetric winding with a center tap voltage difference should be ≤ ± 2%.
General small power transformers allow a heating rate of 40 ℃ ~ 50 ℃, if the insulating material of good quality, can also improve the allowable temperature rise.
H, detection distinguish the end of each winding of the same name. Power transformer, and sometimes in order to obtain the required secondary voltage can be two or more secondary windings connected in series to use. The power transformer in series, the series winding side of the same name must be properly connected, can not be wrong. Otherwise, the transformer can not work properly.
I, the discriminant power transformer short-circuit fault detection. The main symptoms of the power transformer short-circuit fault is a severe fever and secondary winding output voltage is abnormal. Typically, within the coil interturn short-circuit point more, the greater the short-circuit current, the transformer fever more serious. The simple method of testing to determine whether the power transformer short-circuit fault is a measure of no-load current (in front of the test method has been introduced). The presence of short-circuit fault of the transformer, its no-load current value will be greater than 10% of full load current. Severe short-circuit, the transformer no-load power within tens of seconds will quickly heat, touch the core there wi ll be a hot feeling. At this point do not measure the no-load current can be concluded that the transformer short-circuit point.
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