f = PN/120 where f is frequency of power supply, P is number of poles in the machine and N = speed in rpm. So, Synchronous speed N = 120f/P. Thus for 50 Hz supply, 2 pole machine; synchronous speed = 3000rpm. ETRICAL
Within our solar system quite a bit of exploration has been done by spacecraft including orbiters and landers. Planets outside our solar system will be difficult or impossible to explore with spacecraft in our lifetimes, so astronomers and astrobiologists use other techniques to search for signs of life on these planets. In particular, astronomers are interested in planets within the habitable zone of stars.
If a planet can be on the opposite side of Earth from the Sun, its orbital path around the Sun is, by definition, outside of Earthâs orbit. Located inside Earth's orbit, Venus and Mercury are called âinferior planets.â Located outside, Mars and the rest are called âsuperior planets.â When a superior planet is 180 degrees from the Sun from the vantage point of Earth, it is said to be at opposition.