Mushin kala bixinta 3-xagga waa mushin oo loo isticmaalaa inuu badalo xidhka xisbiyada dhexdooda (medium voltage) ilaa xidhka xisbiyada yar (low voltage) si loo kala bixo xidhka 3-xagga. Wuxu ugu badan yahay ee ku saabsan xidhka xisbiyada degmada sababtoo ah taas oo ka dhigaa in la isticmaalo xidhka 3-xagga ee maamulaha industriya, guryaha aqoonta, xidhka xisbiyada ummaha, iyo xidhka xisbiyada ee ku saabsan xidhka xisbiyada.
Qaabka ugu weyn ee transformerka sannadaha 3 waa inay goobta la xidhiidho. Ammaanka midig ka soo baxa koonfurka, guriga qalabka, xariirka hoosee, ama koonfurka la xidhiidho (ring main unit) ayaa ku soo galiya transformerka ee ku jira goobta ka hor, oo waxa uu ku badbaadiyo goobta hoosee. Goobta hoosee ayaa si kasto ah u isticmaalaya motorada, dhaqanka, isku dhafan (HVAC), pumpada, elevatorka, chargerada, qalabka ujeedada, iyo qalabka kale ee ammaanka.
TSTY ayaa siinaya foomiyeedka sannadaha 3 ee goobta la xidhiidho kaasoo leeyahay qaabka kala duwan. Transformerkii oil-immersed ayaa mararka qaar isticmaalka ka dhigan koonfurka hoosee, shabakadda ammaanka, goobta iyo qalabka, xariirka degmada, iyo koonfurka xagga hoosee. Transformerkii dry-type ayaa mararka qaar loo isticmaalaa goobta dhexe ee ammaanka, guryaha caalamiga, hospitalada, iskolada, marka iyo goobta aan la isticmaalin oil.
Ku saabsan xiloolka farsamada ee kooxka saddex, waxa loo baahan yahay in la dooro qalabka ku saabsan: qalabka la isticmaalo (rated capacity), jirka ugu horreysa (primary voltage), jirka ugu dambeysa (secondary voltage), frekweynta, kooxka vector (vector group), xadka xadka (impedance), meelaha lagu bixi karo (tap range), xadka islaamka (insulation level), waxyaalaha lagu abuuray xadka (winding material), habka ku saabsan dhaqanka (cooling method), xadka xadka (noise requirement), xadka xadka (loss level), iyo xadka xadka (short-circuit withstand requirement). Waxaana loo baahan yahay in la helego xaaladaha guri (site conditions) sida: sarraarka (altitude), jirka dhulka (ambient temperature), xadka xadka (humidity), dhulka (dust), dhaqanka (ventilation), xadka xadka (corrosion exposure), iyo in ay ku dhaqaaqdo guri ama dibadda (indoor or outdoor installation) ilaa markii la sameeyo qorshaha.
Xiloolka farsamada ee kooxka saddex waa inuu leeyahay nooca xadka (load type). Iyadoo la isticmaalo kooxka ugu badan oo ka mid ah xiloolka iyo qalabka (motor-heavy industrial systems), waa in la eegto xadka xadka (starting current) iyo xadka xadka (load fluctuation). Iyadoo la isticmaalo guryaha caafimaadka (commercial buildings), waa in la eegto xadka xadka (HVAC operation), xadka xadka (elevators), xadka xadka (lighting), xadka xadka (office equipment), iyo xadka xadka (future load expansion). Iyadoo la isticmaalo xiloolka caafimaadka (utility distribution), waa muhiim in la eegto xadka xadka (overload practice), xadka xadka (line voltage drop), habka xadka (grounding method), xadka xadka (protection fuses), iyo xadka xadka (transformer placement).
TSTY wuxuu karaan ku caawinaa isticmaalayaasha inay xidhiidhaan transformaarka ee jiritaanka sannadka ah ee ku saabsan kala duwan ee qofka ka hor iyo qofka ka dambe. Kaliya midig ee jiritaanka, transformaarku waxaa la xidhiidhaa RMU switchgear, MV circuit breaker panels, load break switches, fuses, ama dhaqsoodhaha ka soo baxa. Kaliya hoose ee jiritaanka, waa la xidhiidhaa LV switchboards, busbar trunking, metering panels, capacitor banks, iyo distribution feeders.
Booqooyinka substation oo ku yaal, transformaarka ee jiritaanka sannadka ah waxaa la sameeyaa midig ugu dambeyn ee MV switchgear compartment iyo LV distribution compartment. Tani waa la sameeyaa, si aad ugu yar taagto, kuwaasoo leh meelaha uu ku qoran yahay, meelaha uu ku qoran yahay, meelaha uu ku qoran yahay, meelaha uu ku qoran yahay, meelaha uu ku qoran yahay, iyo meelaha uu ku qoran yahay. Boqorka ka soo baxa, waxaa loo baahan yahay inaad ugu yar taagto, meelaha uu ku qoran yahay, meelaha uu ku qoran yahay, meelaha uu ku qoran yahay, iyo meelaha uu ku qoran yahay.
Marka la oodan doono transformerka ee ku saabsan kala goynka sannadaha, waxyaalaha la baahan yahay waa: jiritaanka xisaabta, qaybta voltijka, frekweynta, qaybta la xidhiidha, xaaladda impedaanska, nooca ee ka badbaadinta qaybta, habka guurka, habka la saaray, xaaladda gacanta, liiska waxyaalaha la isticmaalayo, qaybaha la isticmaalo, iyo warqadaha la baahan yahay. Haddii transformerkuu loo isticmaalo si loo soo diriyo dalka kale, waxyaalaha la baahan yahay waa: habka la saaray, xaaladda guurka, luqada warqadka nameplate, warqadaha tijaabada, iyo xaaladda taariikhda dhulka la soo diriyo.
TSTY wuxuu kuu bixi karaa warqadaha xisaabta, rasmiga awoodaha, warqadaha tijaabada, taariikhda waxyaalaha la isticmaalayo, taariikhda saarida, iyo taariikhda nameplate oo kala duwan ee ku saabsan qaybta la isticmaalo. Transformerka ee ku saabsan kala goynka sannadaha ayaa caawinaya in timmada la isticmaalo xisbiyada jiritaanka, xisbiyada transformerka, xisbiyada kala goynka voltijka yar, iyo xaaladda la saaray ee guriga.