Understanding Delta & Star Load Connections

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Discussion Overview

The discussion revolves around the necessity and functionality of delta and star load connections in three-phase systems, as well as the limitations of connecting loads in parallel or series as done in single-phase AC systems.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants inquire about the reasons for requiring delta and star load connections, suggesting these are fundamental configurations for three-phase systems.
  • One participant notes that delta loads can typically connect to a star (wye) power system without using the neutral, implying a relationship between the two configurations.
  • There is a question regarding the feasibility of connecting loads in simple parallel and series configurations as in single-phase AC, with participants expressing curiosity about the limitations of such approaches in three-phase systems.
  • Another participant mentions that series connections can be made under certain conditions, specifically with transformers, and discusses the need for vector arithmetic to determine outcomes in different configurations.
  • Concerns are raised about the potential for high circulating currents when paralleling secondaries due to phase angle differences, while also noting that a closed delta configuration can minimize these currents.
  • One participant asserts that powering a single-phase load from all phases to maintain balance is not possible, indicating a limitation in the approach.

Areas of Agreement / Disagreement

Participants express curiosity and raise questions about the topic, but there is no consensus on the necessity or implications of delta and star connections, nor on the feasibility of alternative configurations.

Contextual Notes

Participants have not fully explored the assumptions behind their claims regarding load connections and the implications of different configurations, leaving some aspects unresolved.

amaresh92
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why do we require delta and star load connection ?
thanks.
 
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Perhaps you should first tell us what type of alternative load connections you are proposing.
 
amaresh92 said:
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?
 
Skaperen said:
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 can't connect it as simple parallel and series as in case of single phase ac?
thanks
 
amaresh92 said:
why we can't 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.
 

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