MODULE V - Electrical engineering

MODULE V Electrical engineering - Basics Page 12

2. Electric circuits

One speaks of a closed electric circuit if there is an electron flow between two poles over a conductor including resistors. The electrons flow from the negative pole (-) to the positive pole (+). Resistors in this sense can be e.g.: electric machines, electric devices, measuring instruments, electric components, light bulbs, etc... These resistors are also called power consumers.

In diagram 14, which shows a simple closed electric circuit, measuring elements for the measurement of the electric current and the voltage are drawn in using specially defined symbols according to DIN 40900 (German Industry Norm). Furthermore, voltage supply and resistance (power consumers) are drawn in with their corresponding symbols as well:

Diagram 14: Simple closed electric circuit

If one connects an electric device to a power supply one always has to pay attention to the operating voltage of this particular device.
If an electric device was designed for a voltage of 230V it can e.g. not be operated with a voltage of 110V since the amperage of this voltage is too small.
If an electric device that was designed for a voltage of 110V is connected to a voltage of 230V it will probably be destroyed since the amperage of this voltage is too high. One normally finds the electric operating information for an electric device on its rating plate or in its corresponding operating manual.

Diagram 15: Rating plate for a three-phase motor