what should always be check when changing a transformer ? course hero

What causes a terminal to discolor?

Who checks furnace airflow?

What would a visual inspection reveal?

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Unit 61- Troubleshooting Electric Heat

Unit 60 Electric Heat Installation Flashcards | Quizlet

Study with Quizlet and memorize flashcards containing terms like The minimum distances from each of the furnace surfaces to any combustible materials describes which of the following?, Why should electric furnaces not rest directly on the ceiling joists?, Compared to the installation of a gas or oil furnace, an electric furnace installation is? and more.

UNIT 59 Electric Heat Flashcards | Quizlet

Study with Quizlet and memorize flashcards containing terms like What is the formula to figure out how much electric heat is produced by a furnace?, Baseboard heaters are ideally suited for where?, An advantage of a warm air electric furnace compared to an oil or gas furnace is and more.

What causes a terminal to discolor?

Overheating can cause a terminal to discolor or the wiring insulation to melt. What should you consider when repairing the wire or the terminal?

Who checks furnace airflow?

The technician should check the furnace airflow.

What would a visual inspection reveal?

A visual inspection might reveal a broken heating element, an open fusible link, and a cracked ceramic insulator. Which of these parts must be replaced?

How to test a transformer?

Upon completion of this course, the participant should be able to: 1 Understand the basic operation of a transformer. 2 Understand turns ratios and calculate terminal voltage and current. 3 Understand terminal markings and various single phase and three phase wiring schemes. (WYE vs DELTA). 4 Understand how to perform a polarity test on a potential transformer. 5 Understand the electrical testing methods performed on transformers such as insulation resistance testing, excitation and power factor testing. 6 Understand the various tests performed on insulating oil.

What are the tests performed on transformers?

Understand the electrical testing methods performed on transformers such as insulation resistance testing, excitation and power factor testing.

What is the function of transformers?

Electrical Transformers serve the crucial function of transforming voltage potential to a higher or lower values to meet the appliances and machinery voltage level requirements. Improper use, maintenance and neglect can cause heavy losses to businesses as well as to the environment.

What is the purpose of a transformer?

Power stations use electrical transformers to increase voltage. Sub-stations use electrical transformers to decrease voltage. Even your smartphone and laptop use transformers to charge their batteries. But what are transformers? How do they work? And why do we need them? This course will help you answer all of these questions and many more!

What do power stations use to increase voltage?

Power stations use electrical transformers to increase voltage. Sub-stations use electrical transformers to decrease voltage. Even your smartphone and laptop use transformers to charge their batteries.

Is electrical engineering knowledge beneficial?

Some electrical engineering knowledge is beneficial, but lessons are explained in depth to allow students to build their knowledge from the ground up. A bit of background engineering knowledge would be useful but is not essential.

How to test a transformer?

Both the primary and secondary terminals of the transformer should be isolated from external connections, and measurements made on each phase of all windings. Test equipment connections should be made in the following order: 1 Ground – Ensure that the transformer is first grounded directly to local station ground and then attach the test set ground. 2 Accessories – Connect any desired accessories, such as remote controls, warning beacon, PC, etc. 3 Test Leads – With the test leads disconnected from the device under test, connect the current and voltage leads to the test set and verify tightness of all connections. 4 Connect to the transformer – Each transformer configuration requires different test connections, some examples are provided in the next section. Extra care should be taken to prevent leads from falling off while testing, or connecting leads on top of or too close to one other. Voltage leads should always be placed inside (between) current leads and the transformer. 5 Input power – Plug in the test set. Before making this connection, ensure that the power source ground has a low impedance path to the local station earth ground.

Why do transformers have tap changers?

Many power and distribution transformers are equipped with tap changers to increase or decrease the turn's ratio depending on the supply voltage. Because changing ratio involves a mechanical movement from one position to another, each tap should be checked during a winding resistance test.

How to measure transformer winding resistance?

Transformer winding resistance measurements are obtained by passing a known DC current through the winding under test and measuring the voltage drop across each terminal ( Ohm's Law ). Modern test equipment for this purposes utilizes a Kelvin bridge to achieve results; you might think of a winding resistance test set as a very large low-resistance ohmmeter (DLRO).

What is winding resistance test?

Winding resistance test equipment is available in a variety of styles based on specific applications. A test set used for a power transformer would be much different than one designed for small instrument transformers. No matter what the type, winding resistance testers are always equipped with a current output, voltage measurement, and resistance meter. Photo: Testguy

Why do transformers change windings?

Winding resistance in transformers will change due to shorted turns, loose connections, or deteriorating contacts in tap changers. Regardless of the configuration, the resistance measurements are normally made ...

How long does a transformer drift?

For small transformers the drift lasts for only a few seconds; for single-phase high voltage transformers the drift may last for less than a minute; for large transformers the drift time required could last a couple minutes or more. Any change in current will cause the resistance value to change.

What is demagnetizing transformers?

Demagnetizing a transformer removes the residual magnetic flux caused by passing a polarized direct current through the windings during resistance testing. Photo: Wikimedia.

What causes a terminal to discolor?

Overheating can cause a terminal to discolor or the wiring insulation to melt. What should you consider when repairing the wire or the terminal?

Who checks furnace airflow?

The technician should check the furnace airflow.

What would a visual inspection reveal?

A visual inspection might reveal a broken heating element, an open fusible link, and a cracked ceramic insulator. Which of these parts must be replaced?