Transformer input four wires, work probably only two, the power supply for 220V, the fire wire connected to the "220V" end, the zero line connected to the "zero" end. After the primary side of the power supply, measuring the secondary side should be measured 6.3V open-circuit voltage. If there is no voltage, the transformer is bad.
Problem 2: how to measure the voltage of the transformer A, the detection of mid-week transformer:?
A, will be dialed to the multimeter R × 1 block, according to the mid-week transformer winding pins arranged in accordance with the law, one by one to check the winding on and off, and then determine whether it is normal.
B, test insulation performance: the multimeter will be placed in the R × 10k block, do the following state test:?
(1) the resistance between the primary and secondary windings;?
(2) the resistance value between the primary winding and the shell;?
(3) the value of resistance between the secondary winding and the case.
The above test results are divided into three cases:?
(1) resistance value is infinity: normal;?
(2) resistance value of zero: a short-circuit fault;?
(3) resistance value is less than infinity, but greater than zero: leakage fault.
Second, the detection of power transformers:?
A, by observing the external appearance of the transformer to check whether there are obvious anomalies. Such as the coil lead is broken, de-welded, whether the insulating material has burnt traces, whether the core fastening screw is loose, silicon steel sheet has no corrosion, winding coil is exposed, etc..
B, insulation test. With a multimeter R × 10k block were measured with the primary core, primary and secondary, core and secondary, electrostatic shielding layer and secondary, secondary windings between the resistance value, the multimeter pointer should be pointed at infinity position. Otherwise, the transformer insulation performance is poor.
C, coil on-off detection. The multimeter will be placed in the R × 1 block, the test, if a winding resistance value of infinity, then the winding has a circuit-breaking fault.
D, identify the primary and secondary coils. Power transformer primary and secondary pins are generally from both sides of the lead, and the primary winding more marked with 220V, secondary winding is marked with the rated voltage value, such as 15V, 24V, 35V, etc.. Then according to these markings to identify.
E, no-load current detection.
(1) direct measurement method. All windings of the secondary will be open-circuit, the multimeter is placed in the AC current block (500mA, strung into the primary winding. When the primary winding plug into the 220V AC mains, the multimeter is indicated by the no-load current value. This value should not be greater than the transformer full load current of 10% to 20%. General common electronic equipment power transformer should be in the normal no-load current of about 100mA. If too much, the transformer has a short-circuit failure.
(2) indirect measurement method. In the primary winding of the transformer in series with a 10?/5W resistor, the secondary is still all no-load. Dial the multimeter to the AC voltage block. After charging, with two pens to measure the voltage drop U at both ends of the resistor R, and then use Ohm's law to calculate the no-load current I empty, that is, I empty = U / R.
F, no-load voltage detection. The primary power transformer connected to the 220V mains, with a multimeter AC voltage connected to measure the winding no-load voltage value (U21, U22, U23, U24) should meet the requirements of the value of the permissible range of error is generally: high-voltage windings ≤ ± 10%, low-voltage windings ≤ ± 5%, with the center of the symmetrical tap of the two groups of windings should be ≤ ± 2% voltage difference.
G, the general small power transformer allows temperature rise of 40 ℃ ~ 50 ℃, if the insulation material used is of good quality, the allowable temperature rise can be increased.
H, detection and identification of the winding of the same name end. In the use of power transformers, sometimes in order to get the desired secondary voltage, two or more secondary windings can be used in series. Using series connection method when using power transformer, participate in the series connection of the winding of the same name end must be connected correctly, can not be mistaken. Otherwise, the transformer can not work properly. i. power transformer short circuit fault comprehensive detection of discrimination. Power transformer short-circuit failure occurs after the main symptom is a serious heat and secondary winding output voltage abnormality. Usually, the more short-circuit points between turns within the coil, the greater the short-circuit current, and the more serious the transformer heating. Detection to determine whether the power transformer has a short-circuit failure of the simple method is to measure the no-load current (test method has been described earlier). There is a short-circuit fault transformer, the value of its no-load current will be much larger than the full-load current of 10%. When the short-circuit is serious, the transformer in no-load power within a few tens of seconds will quickly heat up, touch the iron core will have a hot feeling. At this time, without measuring the no-load current can be concluded that the transformer has a short-circuit point exists.... >>
Question 3: How to measure the insulation resistance of the transformer? Measurement of transformer insulation resistance, for the voltage level of 10kV power transformer, we usually use 2500V megohmmeter (commonly known as shaking table). Before the test should be transformer high and low voltage side of each phase of the pile head fully discharged, discharge the transformer internal residual charge (transformer belongs to the capacitive electrical equipment), before the test. Test, insulation shaking table should be placed in a horizontal position, holding the insulation shaking table insulation parts, observe the table pointer slowly rise with shaking, at infinity instantaneous short two terminals: L and E. Will find the pointer for "O". Fang can continue to use the shaking table to test insulation resistance. Transformer insulation is divided into "high (voltage) to low (voltage), high (voltage) to the ground, low (voltage) to the ground" three kinds of cases, such as transformer insulation resistance is found to be obvious difference, should use the shielding method of testing (will be the high and low voltage side pile head casing with a copper wire shorted to the rocking table shielding pile head), using the shielding method should pay attention to shielding the line for the electrified parts, should keep the Hand on the charged parts of the safety distance. If the test, the transformer insulation resistance value rise is not big, that means the transformer internal and high and low voltage casing parts may have been damp, need to dry the transformer processing.
Question 4: How to measure the transformer loss? 1, measuring iron consumption
The iron consumption of the transformer depends on the input voltage, independent of the load.
The input power under no load includes the iron consumption of the transformer and the copper consumption of the primary winding. Transformer no-load operation, measure the no-load input power and no-load current, and measure the DC resistance of the transformer primary winding immediately after power failure. According to the DC resistance and no-load current can calculate the copper consumption of the primary winding.
Transformer iron consumption = no-load input power - primary winding no-load copper consumption.
2, measuring load copper consumption
Load copper consumption including primary winding copper consumption and secondary winding copper consumption. Transformer rated operation, temperature stabilization, measure the input current and output current. Immediately after the power failure, measure the transformer's primary winding and secondary winding DC resistance, according to the current and DC resistance were calculated transformer primary winding copper consumption and secondary winding copper consumption.
3, total loss
Total loss = iron consumption + primary winding load copper consumption + secondary winding load copper consumption.
Note: Accurate no-load input power is very important. And no-load operation, the current distortion is large, the power factor is low, the general test system is difficult to accurately measure, recommended the use of Hunan Galaxy Electric Co.
Question 5: How to measure the transformer impedance? Transformer zero-sequence impedance refers to the zero-sequence current flows through the transformer three-phase symmetrical circuit when the impedance encountered. The zero-sequence impedance characteristics of a three-phase transformer are related to the way the windings are connected. Zero-sequence impedance also depends on the structural arrangement between the windings and the core, and therefore varies when measured on different windings. Zero sequence impedance is also related to the type of core structure. Three-phase three-pillar core structure of the transformer, the zero sequence magnetic flux must pass through the core and the oil tank between the air gap and the oil tank to form a circuit, the zero sequence impedance is smaller. The three-phase five-pillar core structure of the transformer, the zero sequence flux can be formed through the side yoke circuit, so its zero sequence impedance is larger. Therefore, in the actual calculation, the transformer zero-sequence impedance is best to take the measured value
Question 6: How to test the transformer with a multimeter good or bad power transformer is good or bad, through the four-step test, can be considered "good".
1, primary and secondary all coils are not disconnected. Generally small power step-down transformer, the primary coil is thin and more, and therefore easy to break, the secondary is thick and less, rarely broken.
Primary resistance is generally in the tens to hundreds of ohms, the smaller the power, the greater the measured resistance. 181 ohms, normal, estimated for the 4~5W transformer. The secondary resistance is much smaller, should be in a few Europe to 0.few Europe.
2, the primary and secondary coils are not short-circuited, no leakage. With a multimeter high resistance file, the two pens were connected to the primary and secondary coils of each one out of the head, the indication should be more than a few megohms, infinity is better.
3, primary and secondary coils are not short-circuited with the core, no leakage. Refer to point 2 measurement.
4, the primary and secondary coils do not have a short circuit between turns. If the empty tripod on the power, the transformer is abnormally hot, we must think of this reason. And, turn-to-turn short circuit can not be measured with a multimeter.
Question 7: Simply tell me how to measure the transformer is good or bad First, from the appearance of the transformer to see if it is burnt,
If the appearance is good, measure the winding resistance of the transformer, the primary coil is generally a few hundred ohms to a few thousand ohms, and the secondary coil is generally less than 10 ohms. Then measure the insulation resistance between the windings and the core,
If the resistance is basically normal, you can try to energize, measure the output voltage is normal,
If you meet the requirements, then the transformer is good.
Question 8: How to measure the input of this transformer is how much, the output is how much 100 points From the shape, this is a small power transformer.
The parameters of the transformer are usually labeled on the body. If not, you can judge according to the following methods:
1, use a multimeter to measure the resistance of the red line on one side and the resistance of the yellow and black lines on the other side. The same color is the same winding. If the red line resistance value than the other side of the winding value is much higher, can be roughly judged to be the high-pressure side, and the other side of the yellow and black line is the load winding.
2, the transformer high-voltage winding (220V or 380V) is generally indicated by the red line.
3, connect the power supply test. Find a power cord with 220V plug and a 2A fuse in series, access to 220V. If the insurance is not burned, use a multimeter to measure the voltage value of each winding on the other side. If measured such as 6V, 12V or 24V, you can immediately determine the original rated voltage of the transformer is 220V. If measured is the other value, in fact, waste utilization is also good.
Question 9: how to measure the number of turns of the transformer 1, the number of turns of the transformer, the general instrumentation is not measured; only by calculating or actually removing the winding according to the transformer's input (output) voltage divided by the total number of turns of the winding input (output) coil, it will be calculated how many turns per volt.
2, according to the transformer voltage, power, cross-sectional area of the core, frequency, flux density (check the transformer manual) to calculate the number of turns of the transformer. See the formula:
Commonly used small transformer turns per volt formula: N = 10,000/4.44FBS
Here: N - turns per volt, F - AC frequency (our country for 50HZ), B - flux density, S -core cross-sectional area
The flux density generally varies from material to material, common silicon steel sheet to take 1.2-1.7 or so.
According to this formula, you measure the transformer core size, calculate the cross-sectional area, you can deduce the number of turns per volt. After knowing the number of turns per volt, you can easily calculate the number of primary and secondary line turns.