A polyphase circuit refers to an electrical circuit that consists of multiple alternating current (AC) voltage or current sources, usually with a phase difference between them. These circuits are commonly used in power distribution systems and electric machines to efficiently transmit and utilize electrical energy. One common configuration of a polyphase circuit is the delta connected system, also known as the delta connection.
In a delta connected system, three voltage or current sources are connected in a triangular arrangement, resembling the Greek letter "Δ" (delta). Each source represents a phase, and the connections between them form closed loops. The key characteristics of a delta connected system are as follows:
Number of Phases: A delta connected system typically consists of three phases, often referred to as Phase A, Phase B, and Phase C.
Phase Voltages and Currents: The voltage or current in each phase of a delta connection can be represented by line-to-line values. This means that the voltage or current measured between any two phases (line-to-line) is the actual voltage or current of that phase. In contrast, in a wye (star) connection, the line-to-neutral voltage or current represents the phase voltage or current.
Phase Relationships: The phase difference between any two phases in a delta connection is typically 120 degrees. This phase displacement is crucial for creating a rotating magnetic field in AC machines, which is used in motors and generators.
Voltage and Current Relationships: In a balanced delta connection (where all three phases have equal magnitudes and 120-degree phase differences), the line-to-line voltage is equal to the square root of 3 times the phase voltage. Similarly, the line current is equal to the phase current.
Advantages: Delta connections are useful in applications where high power is needed, such as industrial motors. They can handle higher voltages and currents compared to wye connections.
Disadvantages: Delta-connected systems do not provide a neutral connection, which can be a limitation in certain applications where a neutral point is required for grounding or for supplying single-phase loads.
Overall, delta connected systems are an essential part of polyphase power distribution and utilization. They are widely used in various industrial and commercial settings, especially where high power levels and efficient utilization of three-phase power are needed.