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to test series and interpoles (commutating) fields from a DC motor; to determine phasing and polarity in multiwinding armatures; to test rotors in rotating frequency changers, as well as in wound rotors; to test shorts between turns in taped coils before installation into an armature or a stator; as a low voltage isolation transformer
A receptacle tester being used to check for some types of improper wiring of an outlet. For this particular tester, proper wiring is indicated by the two yellow lights. The outlet tester checks that each contact in the outlet appears to be connected to the correct wire in the building's electrical wiring. It can identify several common wiring ...
Pole mounted distribution transformers are manufactured with additive polarity, while instrument transformers are made with subtractive polarity. Where markings have been obscured or are suspect, a test can be made by interconnecting the windings and exciting the transformer, and measuring the voltages. [4]
A common form of in-circuit testing uses a bed-of-nails tester.This is a fixture that uses an array of spring-loaded pins known as "pogo pins". When a printed circuit board is aligned with and pressed down onto the bed-of-nails tester, the pins make electrical contact with locations on the circuit board, allowing them to be used as test points for in-circuit testing.
Auto-polarity for direct-current readings, shows if the electric polarity of applied voltage is positive (agrees with meter lead labels) or negative (opposite polarity to meter leads). Sample and hold, which will latch the most recent reading for examination after the instrument is removed from the circuit under test.
A 120:120 instrument isolation transformer showing two polarity marking conventions. Voltage transformers (VT), also called potential transformers (PT), are a parallel-connected type of instrument transformer. They are designed to present a negligible load to the supply being measured and have an accurate voltage ratio and phase relationship to ...
The important aspects of condition monitoring of transformers are: [2] Thermal modelling – The useful life of a transformer is partially determined by the ability of the transformer to dissipate its internally generated heat to its surroundings. [3]
The flyback transformer circuit was invented as a means of controlling the horizontal movement of the electron beam in a cathode-ray tube (CRT). Unlike conventional transformers, a flyback transformer is not fed with a signal of the same waveshape as the intended output current.