In electrical engineering, a delta connection is a specific way of connecting three electrical components (often resistors, capacitors, inductors, or transformer windings) in a three-phase electrical system, forming a triangular, closed-loop configuration.
Understanding the Delta Connection
The "delta" refers to the triangular shape (resembling the Greek letter Δ) formed by the interconnection of the three components. The supply voltage is connected to each of the three vertices (junctions) of the triangle, and the load is also connected in a similar fashion, or in a wye configuration.
Key Characteristics:
- Shape: The connection is visually represented as a closed triangle.
- Phases: Used in three-phase power systems.
- Voltage and Current Relationships: In a balanced delta connection:
- Line voltage (voltage between lines) is equal to the phase voltage (voltage across each component in the delta).
- Line current (current flowing in the lines) is √3 times the phase current (current flowing through each component in the delta). This is because the line current splits and flows through two delta-connected components.
Advantages:
- Higher Starting Torque (Motors): Delta connections are sometimes used for starting induction motors, initially connecting them in delta to provide higher starting torque.
- Continued Operation with One Phase Down: If one phase is lost in a delta-connected system, the remaining two phases can still deliver power to the load (though at a reduced capacity). The system becomes unbalanced, but it can continue to operate.
Disadvantages:
- No Neutral Point: Delta connections do not provide a neutral point, which can limit their use in certain applications where a neutral connection is required for single-phase loads or grounding purposes.
- Harmonic Current Issues: Delta-connected transformer windings can trap certain harmonic currents, which can cause overheating and other problems.
Delta vs. Wye (Star) Connections
Delta connections are often compared and contrasted with wye (or star) connections. In a wye connection, three components are connected at a common point (the neutral point), with the other ends connected to the three phases.
| Feature | Delta Connection | Wye (Star) Connection |
|---|---|---|
| Shape | Triangle | Star (Y) |
| Neutral Point | No Neutral | Neutral Point Available |
| Voltage | Line voltage = Phase voltage | Line voltage = √3 * Phase voltage |
| Current | Line current = √3 * Phase current | Line current = Phase current |
| Applications | Power transmission, motor starting (sometimes) | Power distribution, supplying single-phase loads |
Example Applications
- Power Transmission: Delta connections are frequently used in power transmission systems, particularly in high-voltage applications.
- Transformer Windings: Transformer windings can be connected in delta or wye configurations, depending on the specific application requirements. Delta-delta and delta-wye transformer configurations are common.
- Motor Starting: As mentioned earlier, delta connections can be used for starting induction motors to provide a higher starting torque. After the motor reaches a certain speed, it may be switched to a wye connection to reduce the current draw.
