blindiop.blogg.se - 3 phase motor winding resistance chart pdf

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.

Connect to the transformer – Each transformer configuration requires different test connections, some examples are provided in the next section.

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.

Accessories – Connect any desired accessories, such as remote controls, warning beacon, PC, etc.

Ground – Ensure that the transformer is first grounded directly to local station ground and then attach the test set ground.Test equipment connections should be made in the following order: Photo: Testguyīoth the primary and secondary terminals of the transformer should be isolated from external connections, and measurements made on each phase of all windings. No matter what the type, winding resistance testers are always equipped with a current output, voltage measurement, and resistance meter. A test set used for a power transformer would be much different than one designed for small instrument transformers. Winding resistance test equipment is available in a variety of styles based on specific applications. Obtaining Winding Resistance Measurements.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). 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). Regardless of the configuration, the resistance measurements are normally made phase-to-phase and the readings are compared with each other to determine if they are acceptable. Winding resistance in transformers will change due to shorted turns, loose connections, or deteriorating contacts in tap changers. Measuring the resistance of transformer windings assures that each circuit is wired properly and that all connections are tight. The main purpose of this test is to check for gross differences between windings and for opens in the connections. Winding resistance measurements are an important diagnostic tool for assessing possible damage to transformers resulting from poor design, assembly, handling, unfavorable environments, overloading or poor maintenance. This guide provides an introduction to transformer winding resistance test methods and procedures.