Relay

Model switching and associated delay of relay

Library

Passive Devices

Description

The Relay block models a relay controlled by an external physical signal. In the steady state, the relay behaves as follows:

  • When the physical signal input PS rises above the Threshold parameter, the relay is energized (meaning closed). The common port C connects to the normally open port S2.

  • When the physical signal input PS falls below the Threshold parameter, the relay is not energized (meaning open). The common port C connects to the normally closed port S1.

During switching, the relay behaves as follows:

  • When the relay closes, the C to S1 connection breaks open after delay Time-to-break C-S1 connection. The C to S2 connection closes after delay Time-to-make C-S2 connection.

  • When the relay opens, the C to S2 connection breaks open after delay Time-to-break C-S2 connection. The C to S1 connection closes after delay Time-to-make C-S1 connection.

You can specify break delays that are longer than the close delays to implement a make-before-break behavior.

Basic Assumptions and Limitations

If the PS input changes during the switching process, the block behavior can be inaccurate. The switching delay occurs due to both mechanical inertia and the fact that modeling inertia as a delay requires approximation.

Dialog Box and Parameters

Time-to-break C-S1 connection

Time it takes the connection between ports C and S1 to break apart when the relay is energized. The default value is 0 s.

Time-to-make C-S1 connection

Time it takes the connection between ports C and S1 to close when the relay is not energized. The default value is 0 s.

Time-to-break C-S2 connection

Time it takes the connection between ports C and S2 to break apart when the relay is not energized. The default value is 0 s.

Time-to-make C-S2 connection

Time it takes the connection between ports C and S2 to close when the relay is not energized. The default value is 0 s.

Connected resistance R

Resistance across closed relay contacts. The parameter value must be greater than zero. The default value is 0.01 Ω.

Open-circuit conductance G

Conductance across open relay contacts. The parameter value must be greater than zero. The default value is 1e-08 1/Ω.

Threshold

If the physical signal input rises above this value, the relay is energized. Conversely, if the physical signal input falls below this value, the relay is de-energized. The default value is 0.

Initial connection

For the initial state of the relay, select one of the following options:

  • C to S1 closed, C to S2 open — The common port C connects to the S1 contact. This is the default option.

  • C to S1 open, C to S2 closed — The common port C connects to the S2 contact.

Ports

This block has the following ports:

PS

Physical signal that energizes and de-energizes the relay

C

Common electrical port

S1

Normally-closed electrical port

S2

Normally-open electrical port

See Also

Was this topic helpful?