In a star-delta (or wye-delta) connection, which is commonly used for three-phase electrical systems, the relationship between currents in the star and delta configurations is governed by the way these connections are wired.
### Star (Wye) Connection
In a star connection, each phase of the three-phase load is connected to a common neutral point. Here's how the currents work in this configuration:
1. **Line Current (I_L):** The current flowing through each phase of the load (from the line to the neutral point) is called the line current.
2. **Phase Current (I_Ph):** The current flowing through each phase winding of the load.
In a star connection:
- **Line Current (I_L)** is equal to the **Phase Current (I_Ph)**.
### Delta Connection
In a delta connection, the ends of each of the three windings are connected in a loop, forming a closed triangular shape. Here's how the currents work in this configuration:
1. **Line Current (I_L):** The current flowing through each phase of the load from one line to the next line.
2. **Phase Current (I_Ph):** The current flowing through each winding of the load.
In a delta connection:
- The **Line Current (I_L)** is equal to \(\sqrt{3}\) times the **Phase Current (I_Ph)**.
### Current Relationship Between Star and Delta Connections
When converting from a star connection to a delta connection (or vice versa), the relationship between the line currents and phase currents in each connection type is as follows:
1. **From Star to Delta:**
- The phase current in the star connection is related to the phase current in the delta connection by a factor of \(\sqrt{3}\).
- The line current in the delta connection is related to the phase current in the star connection by the same factor.
Specifically:
- **I_Ph(Star) = I_Ph(Delta) / \sqrt{3}**
- **I_L(Delta) = \sqrt{3} * I_Ph(Star)**
2. **From Delta to Star:**
- The phase current in the delta connection is related to the phase current in the star connection by a factor of \(\sqrt{3}\).
- The line current in the star connection is related to the phase current in the delta connection by the same factor.
Specifically:
- **I_Ph(Delta) = I_Ph(Star) * \sqrt{3}**
- **I_L(Star) = I_Ph(Delta) / \sqrt{3}**
### Summary
- In a **Star Connection**: Line Current = Phase Current.
- In a **Delta Connection**: Line Current = \(\sqrt{3}\) * Phase Current.
When changing from one configuration to the other, these relationships help in calculating the appropriate current values and understanding how the load current distribution shifts between the two connection types.