STS_CTRL
Dual-source transfer switch supervision: break-before-make sequencing, retransfer delay, sync gating and hunting lockout.
When to use it
Use STS_CTRL when a single-corded load is fed from two independent sources through a transfer switch, one source is preferred, and the switch must never bridge the two — while still moving fast enough that the load survives losing the source in service.
Interface
The published port signature. This is the whole of what the block exposes to your program — the implementation body is not shown here and ships with the download.
Inputs
| Port | Type |
|---|---|
| ENABLE | BOOL |
| SRC_A_OK | BOOL |
| SRC_B_OK | BOOL |
| PREFER_B | BOOL |
| SYNC_OK | BOOL |
| A_CLOSED | BOOL |
| B_CLOSED | BOOL |
| BBM_T | TIME |
| RETRANS_DLY | TIME |
| XFER_TMO | TIME |
| STABLE_T | TIME |
| MAX_XFERS | INT |
| ACK | BOOL |
Outputs
| Port | Type |
|---|---|
| ON_SRC | USINT |
| CLOSE_A | BOOL |
| CLOSE_B | BOOL |
| IN_TRANSFER | BOOL |
| XFER_CNT | UDINT |
| ALM_NO_SOURCE | BOOL |
| ALM_XFER_FAIL | BOOL |
| ALM_HUNTING | BOOL |
| ALM_UNSYNC_BLOCK | BOOL |
| ALM_BOTH_CLOSED | BOOL |
| ALM_CFG_ERR | BOOL |
IEC 61499 event interface
EI INIT, REQ·EO INITO, CNF
Supervised control write
STS_CTRL commands a real actuator. It is written to sit underneath your own interlock, permissive and protection logic — not to replace it. Commission it as you would any control block you wrote yourself.
Validation evidence
- Tests
- 12
- Simulated scans
- 292
- Simulator
- v0.1.0
Complete IEC 61131-3 implementation with a published test suite that runs on the vplant simulator. The counts above are that suite, executed on this build.
- Conforms to IEC 61131-3
- Conforms to IEC 61499
Download STS_CTRL — free
Create a free Ri Tech account to download the block. You get the Structured Text body, the Rockwell Add-On Instruction (.L5X), the Schneider Control Expert DFB (.XDB), PLCopen XML, the IEC 61499 function block type (.fbt) and the datasheet.
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