How Do You Know if a Transformer Is Bad

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Transformers are an electrical component that transmit electrical energy betwixt at least two circuits. Transformers regulate the voltage in circuits, just in some cases these can go bad and cause a circuit to not piece of work. You'll demand to identify key data nigh your transformer, like whether it's suffered visible damage and what its inputs and outputs are. Afterwards that, it should be relatively simple to test the transformer with a digital multimeter (DMM). Should you lot go along having problems with the transformer, you'll need to troubleshoot it.

1. ane

   Inspect the transformer visually. Overheating, which causes the internal wiring of the transformer to run at elevated temperatures, is a common cause of transformer failure. This often causes a physical deforming of the transformer or the area surrounding it.

   • If the transformer exterior is bulged or shows what appear to exist burn marks, don't exam the transformer. Instead, replace it.

2. two

   Determine the wiring of the transformer. The wiring should be conspicuously labeled on the transformer. However, it is always all-time to obtain a schematic of the excursion containing the transformer to make up one's mind how it is connected.

   • The schematic for the excursion will exist available in the production information or on the website of the circuit manufacturer.^[ane]

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3. 3

   Identify the transformer inputs and outputs. The first electric circuit will exist connected to the primary of the transformer. This is its electric input. The second circuit receiving power from the transformer is connected to the transformer secondary, or the output.^[2]

   • The voltage being supplied to the primary should be labeled both on the transformer and the schematic.
   • The voltage existence generated by the secondary should exist labeled in the same fashion equally the primary.

4. four

   Make up one's mind the output filtering. It is mutual to attach capacitors and diodes to the transformer secondary to convert the Air conditioning ability from the output to DC power. This data volition not be available on the transformer label.^[3]

   • Generally, yous can find the transformer conversion and output filtering information on the schematic.
   • Look for whether the transformer is AC or DC wherever the voltage is listed on the label.^[four]

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1. i

   Prepare to measure out the excursion voltages. Turn off the power to the circuit. Remove covers and panels as necessary to gain access to the circuits that contain the transformer. Acquire a digital multimeter (DMM) to take the voltage readings. DMMs are available at electrical supply stores, hardware stores, and hobby shops.^[5]

   • Generally, y'all'll need to attach the leads of your DMM to the input lines to verify that the main of the transformer is not shorted. The same process will be used to cheque the transformer secondary.

2. 2

   Ostend the proper input to the transformer. Utilise power to the circuitry. Use the DMM in Ac manner to measure the transformer chief. If the measurement is less than 80 percent of the expected voltage, the mistake could prevarication in either the transformer or the circuitry providing the principal with power. In that case:

   • Separate the transformer from the input circuit. Exam the input with your DMM. If the input power climbs to the expected value, the master of the transformer is bad.
   • If the input ability does not climb to the expected value, then the problem lies non with the transformer, simply with the input circuitry.^{[half dozen]}
   • The input and output on the transformer may be labeled with "input" and "output," or the input might exist a black and white pigtail.^[7]
   • If the transformer has terminals, the input will ordinarily be L, which stands for "line," or hot ability, and North, which stands for neutral, or the neutral power going into that wire. The output volition be the low voltage side.^[8]

3. 3

   Measure the secondary output of the transformer. If at that place is no filtering or shaping beingness performed by the secondary circuitry, use the Air-conditioning mode of the DMM to read its output. If there is, use the DC scale of the DMM.

   • If the expected voltage is not present on the secondary, either the transformer or a filtering or shaping component is bad. Exam the filtering and shaping components separately.
   • If the testing of the filtering and shaping components evidence no problems, then the transformer is bad.^[9]

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1. 1

   Understand the root of the problem. Transformer failure is normally a symptom of a different kind of failure somewhere in the electrical excursion. Transformers generally have long lives, and rarely fire out past themselves.^[10]

2. 2

   Observe replaced transformers. If the problem causing your transformer to curt out is coming from elsewhere in your circuit, it's likely the transformer will fire out again. After you've replaced the transformer, observe it to brand sure this does non happen. If it does, you lot'll need to perform additional tests.

   • An overloaded transformer volition often make snapping and crackling noises. If you hear sounds like these, cut power to the transformer to prevent exhaustion.^[11]

3. iii

   Verify the condition of external fuses, if necessary. If your transformer has an internal fuse, you may not have fuses in the line leading up to the transformer. Otherwise, there should be fuses in the power supply line to the transformer. Bank check to make certain these are in good condition and replace whatsoever that aren't working properly.

   • Blackness, melting, and deforming in fuses are good indications that the fuse has been damaged. Simple remove and supercede these.
   • In some cases, information technology might be hard to tell if a fuse is in adept condition. Attach your DMM to the fuse with ane lead on each fuse end. If current runs through the fuse, information technology's practiced.^[12]

4. 4

   Cheque for overdraw on your secondary. In some cases, the secondary of your transformer may be cartoon too much current, causing it to short out. If y'all accept a multi-tap transformer and you receive the reading "OL" from the secondary, it's likely the secondary is shorted.

   • Test this by hooking upward the secondary to its excursion and using your DMM to test the secondary lines. If the reading is to a higher place the amperage rating for the transformer, the circuit is drawing also much power.
   • Many common transformers have 3 amp fuses. The amperage rating for your transformer fuse may be labeled on the transformer, but will also exist available in the circuit schematic.^[13]

5. 5

   Remove inputs and outputs to determine the source of the failure. For linear fuses, you'll only have one input and output. In this instance, your trouble is either coming from the input circuit or the output circuit. For more complex fuses, remove inputs and outputs to the transformer one past one to determine what component of the entire circuit is causing the short.^[xiv]

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Add New Question

• Question

  Where should I look to notice the input and output of a transformer?

  

  Jesse Kuhlman is a Main Electrician and the Owner of Kuhlman Electrician Services based in Massachusetts. Jesse specializes in all aspects of abode/residential wiring, troubleshooting, generator installation, and WiFi thermostats. Jesse is also the writer of four eBooks on home wiring including "Residential Electrical Troubleshooting" which covers basic electrical troubleshooting in residential homes.

  

  Master Electrician

  Expert Answer

  The input and output on a transformer is almost always going to exist labeled—usually simply with "input" and "output."

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• A buzzing or cracking sound is ofttimes an early sign that a transformer is about to develop a burn.

• Do not assume that the master side and secondary side of the transformer are referenced to the same electrical ground. The transformer primary and secondary are frequently referenced to different grounds. Be aware of this split grounding while taking measurements.

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• While the circuits are exposed and energized for testing, accidental contact with excursion power could cause daze or injury. Impact the excursion only with the probes of the DMM.

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Things Y'all'll Need

• Schematic of the circuit
• Digital Multimeter (DMM)

About This Article

Article Summary X

To examination a transformer with a digital multimeter (DMM), first plow off power to the circuit. Next, adhere the leads of your DMM to the input lines. Apply the DMM in Air-conditioning fashion to measure the transformer chief. If the measurement is less than eighty% of the expected voltage, your problem could be with the transformer or the circuitry providing the principal power. To measure out the secondary output, utilise the Air conditioning mode if in that location'southward no filtering or shaping. Otherwise, use the DC scale to determine what the issue is. To learn how to troubleshoot your transformer, proceed reading!

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Source: https://www.wikihow.com/Test-a-Transformer

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