Household appliances often use a power supply, in case of failure of which it is important to know how to check the transformer with a multimeter. This will significantly reduce the cost of repairing equipment. It will be enough to order a new or repair the old transformer. If you do everything yourself, the savings on diagnostics will be significant.
Methods
It is advisable to familiarize yourself in advance with the question of how to check the transformer with a multimeter. This is the easiest way to troubleshoot and save on repairs. Coils can be diagnosed by measuring resistance in ohmmeter mode. During the measurement process, the goal is to determine the state of the windings by the quantitative characteristics of resistance, current, voltage.
You can figure out how to check a transformer with a multimeter if you consider the simplest electrical circuit. The connections use: load resistance, supply circuit, transformer windings. Measurements are carried out in the ammeter, voltmeter mode. Compare the obtained values with passport values.
External inspection of damagedwindings helps to simplify the diagnostic task and quickly figure out how to check the transformer with a multimeter. First of all, measurements are taken on leads that have insulation damage or charred areas. The resistance is often underestimated in such cases or a short circuit is observed at all.
Resistance
The ohmmeter mode is much more often used when deciding how to check the he alth of a transformer with a multimeter. In the process of the so-called "dialing", the conclusions of the windings are determined if there is no marking. The input winding often has a high resistance of up to hundreds of ohms - this is a step-down transformer.
The smaller the size of the transformer, the higher the resistance of the primary winding will show the measurement with a multimeter. A break will be immediately visible on the screen, as well as a short circuit will show an infinity sign. Each winding output is ringed on the transformer case to eliminate leakage currents. The latter lead to reduced voltage and deviation of the device from the nominal modes.
Voltage
Transformer windings can be checked by measuring input and output voltages. The dt 832 multimeter will help with this, which is first determined with the winding leads in the ohmmeter mode. Voltage is applied to the primary (has a high resistance for step-down devices), a voltmeter is connected to the secondary (less resistance).
In voltmeter mode dt 832 is measureddeviation of the received voltage from the passport data. If the error exceeds 20%, then it can be concluded that the transformer is faulty. In this case, an interturn circuit occurs. The windings should be carefully inspected for charring of the insulation.
When you turn on the network after a while you can smell burning, this continues to melt the insulation. Such a transformer is no longer recommended to be loaded, it has already failed. Another clear indication of an interturn short circuit is the increased heating of the winding at light load or in idle mode.
Nuances
Some transformer windings cannot be chimed. It is recommended to pay attention to the presence of a microassembly soldered into the transformer housing. This may be a rectifier circuit on the output winding or a noise filter.
The winding may not ring with high resistance, the absence of readings in this case does not indicate a malfunction. Also do not forget to check the short to the ground, if the resistance of the windings is in order. Each output of the device is subjected to verification.
Unstable operation of the transformer may be due to voltage fluctuations in the supply network. Moreover, the value of idling, when only the first winding is connected, will be within acceptable limits. Under load, the power will "sag" significantly.
Typical malfunctions
When diagnosing the technical condition of a transformer, the following types of faults are detected:
- Breakwindings - resistance infinity.
- Turn-to-turn short circuit - resistance below table values.
- Voltage and current deviations.
- Short circuit to the body - the winding melts, the supply fuse is activated.
Externally, you can determine the type of transformer, the purpose is determined according to the electrical diagram. The down wire is thicker at the output, the boost wire is thicker at the input. Accordingly, the primary winding of the step-down has a high resistance, and the step-up value has a higher output.
The windings of a powerful device cannot be checked with a multimeter. In this case, special devices and additional electrical networks are used for diagnostics. In ohmmeter mode, you can check almost all household transformers: in chargers, TVs and other devices.
