Karamin Rilayin Tsaye Don Hanyar Gida Da Turon Mote?

Takarda Mafi Yawan Jiki don Inganci Masu Kisan: Tsarin, Zabubbukan da Amfani

A cikin na'urar kisan masu kisan, takarda suka amfani da fuses domin inganta yawan jiki. Amma ba zan iya inganta yawan jiki wanda ya faruwa saboda kisan masu kisan da ya dace, kisan hagu-hagu, ko kisan da ya dace da kisan da ya dace da kisan da ya dace. A gaba, an amfani da takarda mafi yawan jiki ga kisan masu kisan. Wannan takarda mafi yawan jiki shi ne babban wurin da ya yi aiki saboda tsari na takarda, kuma ya fi shi da wannan mafi yawan jiki. Ya yi aiki tare da tsari na takarda wanda ya haɗa a cikin wurin da ya taka tsari, wanda ya baƙe birnin lalace (wurin da aka sanya da abubuwan kirkiro) zuwa kusa. Idan kusan ya kai waɗanda, ya haɗa mekana da ya yi aiki, ta kasa takarda na kontrol. Wannan ya haɗa contactor da ya kasa, kuma ya kasa takarda na gaba, don haka ya inganta kisan masu kisan daga kisan masu kisan.

Takarda mafi yawan jiki suna kula da adadin wurin da ya taka tsari: biyu da uku. Takarda uku suna kula da motoci da ke da phase-loss protection da kuma motoci da ba ke da phase-loss protection. Tsohon series sun haɗa JR0, JR9, JR14, da JR16. Tsari na ampere-second da ya haɗa takarda mafi yawan jiki suna kula da tsari na inverse-time wanda ya dace da kurba na motor da ke da ita: idan kisan masu kisan ya kai, lokacin da ake magance ita ce mai kasa; idan kisan masu kisan ya kisa, lokacin da ake magance ita ce mai ci. Idan ake zaɓe daidai, takarda zan iya magance idan kisan masu kisan ya kai, don haka ya yi amfani da kisan masu kisan da ke da ita daga kisan masu kisan, amma ya inganta kisan masu kisan daga kisan masu kisan.

Saboda hakan, takarda mafi yawan jiki suna amfani da su a cikin na'urar industri don inganta kisan masu kisan.

I. Inganta Kisan Masu Kisan Da Takarda Mafi Yawan Jiki

Tsarin da ake kafa wurin stator na kisan masu kisan yana haɗa tsari na kisan masu kisan da phase-loss current, wanda baki da shi ya nuna tsarin da ya fi shi takarda mafi yawan jiki.

Star (Y) Connected Stator Windings

A cikin star connection, line current yana iya da phase current. Idan kisan masu kisan ya kai, duk phase currents biyu uku suna kai. Idan kisan masu kisan ya dace da kisan masu kisan da ya dace, takarda biyu mafi yawan jiki zan iya inganta kisan masu kisan da uku. Amma idan kisan masu kisan ya ba dace (misali, 4% voltage imbalance zan iya ba 25% current imbalance), ko idan kisan masu kisan da ya dace da kisan masu kisan da ya dace, takarda biyu mafi yawan jiki ba zan iya inganta kisan masu kisan. A cikin hakan, zan iya amfani da takarda uku mafi yawan jiki.

Delta (Δ) Connected Stator Windings

A cikin aiki daidai, line current (I) = 0.58 × phase current (Iφ), da phase current Iφ = 0.58 × line current I. Idan akwai kisan masu kisan da ya dace (misali, fuse tana dace), kamar yadda ake nuna a Figure 1 (da phase B tana dace), saboda impedance na wurin da ke da ita, Ic = Ia + Ib = 1.5Iφ, da Ib = (2/3)Ic. Wannan yana nuna cewa line current ba zan iya nuna phase current daidai, kuma idan ake amfani da line current don inganta, ba zan iya nuna yawan jiki da ke da wurin.

Idan kisan masu kisan da ya dace a kan full load, Ia = 0.58Ie, Ib = 1.16Ie—wannan overcurrent yana iya ba takarda uku mafi yawan jiki da ke da ita magance ita. Amma idan kisan masu kisan da ya dace a kan 64% na rated load, Ia = 0.37Ie, Ib = 0.75Ie. Overcurrent da ke da phase loss ba zan iya ba takarda uku mafi yawan jiki da ke da ita magance ita, amma phase tana da 58% da ke da ita da kisan masu kisan da ya dace, wanda zan iya ba kisan masu kisan da ke da ita dace. Saboda hakan, don kisan masu kisan da ke da delta connection, takarda uku mafi yawan jiki ba zan iya inganta kisan masu kisan; phase-loss protective relays zan iya amfani.

Idan akwai wurin stator da ya dace (misali, kisan masu kisan da ya dace bayan ake kafa wurin lead da terminal, kamar yadda ake nuna a Figure 2), Ia = Ic = Iφ, da Ib = Iφ. Hakan, line current yana iya da phase current, kamar yadda ake nuna a aiki daidai. A cikin hakan, phase-loss protective relay zan iya inganta kisan masu kisan, amma phase-loss protection devices da ke da ita da ke amfani supply-side phase loss ba zan iya nuna ita.

II. Zabubbukan Takarda Mafi Yawan Jiki

Zabubbukan da amfani da takarda mafi yawan jiki daidai shi ne babban littafi, amma kisan masu kisan da ya dace saboda zabubbukan da amfani da takarda mafi yawan jiki ba daidai ba suka faruwa. Saboda hakan, mutane da ba suka amfani ba zan iya duba shi ne:

• Fahimtar model, specifications, da characteristics na kisan masu kisan da ke da ita inganta.

• Type Selection: A cikin yankunan da ke da ita kisan masu kisan da ya dace, amfani da takarda uku mafi yawan jiki don kisan masu kisan da ke da star connection, da kuma phase-loss protective relays don kisan masu kisan da ke da delta connection.

• Current Rating Selection: Zabu rated current na takarda mafi yawan jiki saboda rated current na kisan masu kisan, sannan zabu rated current na heating element. Adjustable range na setting current na heating element zan iya nuna a tables na manufacturer. Idan kisan masu kisan da ya dace ya kai 6 times na rated current da kisan masu kisan da ya dace, set the heating element’s current to equal the motor’s rated current. Don kisan masu kisan da kisan masu kisan da ya dace da impact loads, ko kisan masu kisan da ba ake amfani ba, set the current to 1.1–1.15 times the motor’s rated current.

• Example: Kisan masu kisan da rated current of 30.3 A, starting current 6 times rated, short starting time, and no impact load. Suitable models include JR0-40, JR0-60, or JR16-60. Using JR16-60: relay rated current is 60 A, three-pole type. Select a 32 A heating element, adjustable to around 30.3 A.

• Connection Wire Selection: Amfani da wires da ke da ita daidai ko daidai zan iya ba heat dissipation da takarda mafi yawan jiki. Size na wire zan iya nuna a instructions na manufacturer ko electrical handbooks.

• Kisan masu kisan da kisan masu kisan da ya dace ko cooling: Set the thermal relay’s rated current to 60%–80% of the motor’s rated current.

• Reset Mode: Takarda mafi yawan jiki suna amfani da manual da automatic reset modes, switchable via an adjustment screw. Manufacturers usually ship them in automatic reset mode. The choice depends on the control circuit. As a rule, even if the relay resets automatically, the protected motor should not restart automatically—otherwise, set the relay to manual reset to prevent repeated starts under fault conditions and equipment damage. For example, in manual start/stop circuits using push buttons, automatic reset is acceptable; in automatic start circuits, use manual reset.

III. Precautions During Use

To extend the service life of thermal relays and ensure optimal performance, observe the following:

• Use connection wires at the relay terminals with cross-sections strictly according to specifications.

• Thermal relays cannot provide short-circuit protection—fuses must be installed separately. They are unsuitable for motors with very long starting times, frequent operation, or intermittent duty cycles.

• When installed with other devices, mount the thermal relay below them to avoid heat interference. Clean dust and dirt regularly.

• After tripping, automatic reset occurs within 5 seconds; manual reset requires waiting 2 minutes before pressing the reset button.

• After a short-circuit fault, check the heating element for damage and the bimetallic strip for deformation (never bend the bimetallic strip), but do not remove components.

• When replacing a thermal relay, ensure the new one matches the original specifications.

Conclusion

Only by properly selecting, correctly wiring, and appropriately using thermal relays can effective overload protection for motors be achieved.