three phase ac

[amaresh92]

why do we require delta and star load connection ?
thanks.

[uart]

Perhaps you should first tell us what type of alternative load connections you are proposing.

[Skaperen]

why do we require delta and star load connection ?
thanks.
Those are the two basic ways that three phase is connected with. Note that a delta load can usually be connected with a star (wye) three phase power system by just not using the neutral.

Is there more to you question that I didn't really understand?

[amaresh92]

Those are the two basic ways that three phase is connected with. Note that a delta load can usually be connected with a star (wye) three phase power system by just not using the neutral.

Is there more to you question that I didn't really understand?

why we cant connect it as simple parallel and series as in case of single phase ac?
thanks

[Skaperen]

why we cant connect it as simple parallel and series as in case of single phase ac?
thanks

You can connect in series in certain cases. If you have 3 transformers, each with their primaries powered by separate pases in a normal three phase system, you can wire the secondaries in series. You do have to perform some vector arithmetic (or simply plot it geometrically) to see what you would get in various configurations. With two of them in series (assuming each is 240 volts), you can get a total of 240 volts in one case, or about 415.692 volts in the other case. Three of them in series can be configured for a number of voltages from zero to 480.

Paralleling the secondaries would result in very high circulating currents because of the phase angle difference. But one configuration of three secondaries can form a closed delta with minimal circulating currents (at least at the primary frequency).

If you have a simple single phase load, such as one heating element, and want to power it from all phases to keep things in balance ... sorry, you cannot do that.