minor: the fuse as a thermal model, within IEC 60269 and following ABB's gG curves, as an importable package (fuse/)

CLAUDE.md

@@ -86,6 +86,9 @@ The app supports two modes controlled by the `--desktop` flag:
 - `cmd/simulator/templates/index.html` - Embedded dashboard UI
 - `cmd/simulator/wails.json` - Wails configuration
 
+**Public package:**
+- `fuse/` - each phase's fuse as a thermal model (element, body, holder; I² heating), within IEC 60269-1's gates and following ABB's gG curves for 16-63 A; no dependencies, so an EMS's own simulation (FTW's `go/internal/sitesim`) imports the same model
+
 **Internal packages:**
 - `internal/modbus/server.go` - Modbus TCP server with register storage and logging
 - `internal/modbus/registers.go` - Register definitions, encoding/decoding (U16, I16, U32, I32)

cmd/simulator/app.go

@@ -7,6 +7,7 @@ import (
 	"math"
 	"time"
 
+	"github.com/srcfl/device-simulator/fuse"
 	"github.com/srcfl/device-simulator/internal/modbus"
 	"github.com/srcfl/device-simulator/internal/modbus/devices"
 	"github.com/srcfl/device-simulator/internal/settings"
@@ -906,18 +907,37 @@ func (a *App) UpdateSiteConfig(id int, config map[string]interface{}) error {
 	if baseLoad, ok := config["base_load_w"].(float64); ok {
 		site.BaseLoadW = baseLoad
 	}
-	if fuseSize, ok := config["fuse_size"].(float64); ok {
+	fuseSize, sizeSet := config["fuse_size"].(float64)
+	fuseProfile, profileSet := config["fuse_profile"].(string)
+	if sizeSet || profileSet {
+		size, profile := site.FuseSize, site.FuseProfile
+		if sizeSet {
+			if fuseSize != math.Trunc(fuseSize) {
+				return fmt.Errorf("fuse size %v A is not whole amperes", fuseSize)
+			}
+			size = int(fuseSize)
+		}
+		if profileSet {
+			profile = fuseProfile
+		}
+		if err := checkFuse(size, profile); err != nil {
+			return err
+		}
+	}
+	if sizeSet {
 		site.FuseSize = int(fuseSize)
 		site.FuseDamage = PhaseLoads{}
+		site.FuseHeat = [3]fuse.Phase{}
 		site.FuseOverload = FuseOverload{}
 	}
-	if fuseProfile, ok := config["fuse_profile"].(string); ok {
+	if profileSet {
 		if _, exists := fuseProfiles[fuseProfile]; !exists {
 			return fmt.Errorf("unknown fuse profile")
 		}
 		if site.FuseProfile != fuseProfile {
 			site.FuseProfile = fuseProfile
 			site.FuseDamage = PhaseLoads{}
+			site.FuseHeat = [3]fuse.Phase{}
 			site.FuseOverload = FuseOverload{}
 		}
 	}
@@ -935,19 +955,19 @@ func (a *App) UpdateSiteConfig(id int, config map[string]interface{}) error {
 	if fb, ok := config["fuse_blown"].(map[string]interface{}); ok {
 		if l1, ok := parseBool(fb["l1"]); ok {
 			if site.FuseBlown.L1 && !l1 {
-				site.FuseDamage.L1 = 0
+				site.FuseDamage.L1, site.FuseHeat[0] = 0, fuse.Phase{}
 			}
 			site.FuseBlown.L1 = l1
 		}
 		if l2, ok := parseBool(fb["l2"]); ok {
 			if site.FuseBlown.L2 && !l2 {
-				site.FuseDamage.L2 = 0
+				site.FuseDamage.L2, site.FuseHeat[1] = 0, fuse.Phase{}
 			}
 			site.FuseBlown.L2 = l2
 		}
 		if l3, ok := parseBool(fb["l3"]); ok {
 			if site.FuseBlown.L3 && !l3 {
-				site.FuseDamage.L3 = 0
+				site.FuseDamage.L3, site.FuseHeat[2] = 0, fuse.Phase{}
 			}
 			site.FuseBlown.L3 = l3
 		}