Open Circuit Test
The open circuit test, also commonly called a no-load test, is designed for discovering the magnetic properties of a DC machine. For this test, the machine is operated at rated speed but without loading it. The armature current is measured with different field currents and is used to draw the open circuit characteristic curve.
Formula:
EOC = V – Ia(Ra + Rs )
where
- EOC is open circuit voltage,
- V is applied voltage,
- Ia is armature current,
- Ra is armature resistance,
- Rs is series field resistance.
This curve is also a very useful tool that is used to analyze the magnetic properties of the machine, like the connection between field current and generated voltage. It enables ascertaining as well concerning any anomalies existing in the magnetic circuit of the machine, for example, air gap or magnetic saturation.
Testing of DC Machine
The direct current (DC) machines have been from the beginning of electrical engineering studies, since the end of the 19th century. They are used in many different industries such as manufacturing and transportation, and they are still applicable even though the current age is digital. The quality performances and dependability of these machines are the most important factors during their whole lifespan. This is why they are subject to extensive testing.
Testing is a tool that helps us to determine the functions of the machine, show if there are any mistakes, and correct them if needed. It also serves to define the instrument, which is an important criterion of its energy conservation and cost-effectiveness. Here we will consider the DC machine’s test type, procedure, and value.
Table of Content
- Definition of Testing
- Types
- Open Circuit Test
- Short Circuit Test
- Load Test
- Determination of Efficiency
- Applications