## Three-Phase Ports

In Simscape™ Electrical™ software, you can connect the phases of a three-phase system between blocks using two types of ports.

• Composite three-phase port

• Expanded three-phase port

Composite three-phase ports represent three individual electrical conserving ports with a single block port. You can use composite three-phase ports to build models that correspond to single-line diagrams of three-phase electrical systems. Instead of explicitly connecting each phase of the three-phase system between blocks, you connect all three phases using a single port. You can connect composite three-phase ports only to other composite three-phase ports.

Expanded three-phase ports represent the individual phases of a three-phase system using three separate electrical conserving ports. You individually connect each phase of the three-phase system between blocks. Electrical conserving ports can connect directly to electrical components from the Simscape and Simscape Electrical libraries.

Composite three-phase ports produce results with the same fidelity as expanded three-phase ports. Both connection methods consider instantaneous phase voltages and currents and are suitable for modeling balanced and unbalanced three-phase electrical power systems. Each electrical conserving port in an expanded three-phase port has a Through variable of scalar current and an Across variable of scalar voltage. For a composite three-phase port, the Through variable is a three-element current, and the Across variable is a three-element voltage.

You can use the Phase Splitter block to expand a composite three-phase port into separate electrical conserving ports. The separate electrical ports can then connect to Simscape Electrical electrical components.

The figure shows two simple circuits that contrast the composite and expanded connection methods. The two circuits produce the same results.

The top circuit uses a Voltage Source block with a composite three-phase port ~. The bottom circuit uses a Voltage Source block with expanded electrical conserving ports a, b, and c. In each circuit, the instantaneous phase voltages and currents are the same.

### Expand and Collapse Three-Phase Ports on a Block

Simscape Electrical blocks that have composite three-phase ports have an option to switch between composite and expanded ports.

To switch between composite and expanded ports, double-click the block, then set the Modeling option or the Electrical connection parameter to either ```Expanded three-phase ports``` or `Composite three-phase ports`.

For blocks with a single composite port ~, the expanded electrical ports are labeled a, b, and c. For blocks with more than one composite port ~1 and ~2, the expanded electrical ports are labeled a1, b1, c1 and a2, b2, c2.