Himayar Motor: Turukan Da Gaba-Gaban Da Aikacewa
Sistem zabe masu kirki shi ne kungiyar wurare da tattalin da suka samun hankali ga wani kirki mai elektrik don sauya daga jama'a da kuma lalace. Kirki mai elektrik shi ne muhimmiyar yadda a cikin damar da ke gudanar da suka yi a kan al'adu da kuma al'umma, tare da wasu abubuwa mafi yawa zuwa masu karfi. Saboda haka, ita ce muhimmiya da a tabbatar da aiki da na kula da dalilin kirki da kuma tushen.
A wannan takardan, za a hada da nafin da ke gudanar da abubuwan da suka haifar da kirki, nafin da ke gudanar da wurare da suka zaba masu kirki, da kuma tattaunawa da suke zaba saboda National Electrical Code (NEC) da kuma siffofin kirki.
Me Ke Nafin Haifar Da Kirki?
Haifar da kirki shi ne yanayin da ya ba kirki ya ci gaba da na kula ko kuma ya faɗa. Haifar da kirki za su faɗa a bari biyu:
Haifar da na farko: Waɗannan su ne haifar da suka faruwa daga tushen kasa ko kuma abubuwan da suka gudanar da kirki. Wasu misalai na haifar da na farko sun hada da:
Farkon kasa mai tsawon voltage: Wannan ya faru a lokacin da tsawon voltages ta goma sha ɗaya ba da adadin magana ko kuma tushen magana. Wannan za iya ba da tsaro na farko da kuma tsaro na farko a cikin kirki, wanda ya ba da lafiya da kuma tsaro na farko.
Voltage mai tsawo: Wannan ya faru a lokacin da voltage ta goma tsawo da ƙarin da na kirki. Wannan za iya ba da tsaro mai tsawo, current mai yawa, da kuma tsaro mai tsawo a cikin kirki.
Phase sequence mai yau: Wannan ya faru a lokacin da tsari na phase ta goma yau. Wannan za iya ba da hirna mai yau a cikin kirki, wanda ya ba da lafiya da kuma kirki.
Loss of synchronism: Wannan ya faru a lokacin da synchronous motor ta goma hankali da frequency na kasa. Wannan za iya ba da slip mai yawa, hunting, da kuma kalmomi mai tsawo a cikin kirki.
Haifar da na uku: Waɗannan su ne haifar da suka faruwa daga kirki ko kuma abubuwan da suka gudanar da kirki. Wasu misalai na haifar da na uku sun hada da:
Bearing failure: Wannan ya faru a lokacin da bearing da suka taimakawa shaft na kirki ta goma yau ko kuma ya ɗaya saboda friction, masu halin kuɗi, ko kuma stress mai kyau. Wannan za iya ba da karshe, kusa, shaft misalignment, da kuma stalling a cikin kirki.
Overheating: Wannan ya faru a lokacin da temperature na kirki ta goma tsawo da ƙarin da thermal limit saboda overloading, insufficient cooling, ambient conditions, ko kuma insulation breakdown. Wannan za iya ba da lafiyar da insulation, winding damage, da kuma kalmomi mai tsawo a cikin kirki.
Winding failure: Wannan ya faru a lokacin da windings na kirki ta goma short-circuited ko kuma open-circuit saboda insulation breakdown, mechanical stress, ko kuma haifar da na farko. Wannan za iya ba da sparks, smoke, fire, da kuma loss of torque a cikin kirki.
Earth fault: Wannan ya faru a lokacin da phase conductor na kirki ta goma gida da wani part na circuit ko kuma equipment da suka guda. Wannan za iya ba da high fault currents, damage to the insulation and equipment, da kuma potential shock hazards.
Haifar da kirki zai iya ba da lafiya mai yawa ga aiki, kula, da kuma shekarun kirki da tushensa. Saboda haka, ita ce muhimmiya da a bayyana da a zaba saboda su da wurare da tattalin da suka hukuma.
Me Ke Nafin Wurare Da Suke Zaba Masu Kirki?
Wurare da suke zaba masu kirki shi ne wurare da suke duba da kuma hukuma wata ko kusan parametere na kirki ko tushensa, kamar current, voltage, temperature, speed ko kuma torque. Dalilin wurare da suke zaba masu kirki shi ne don in sauya da kuma kalmomi mai tsawo ga kirki da tushensa a lokacin da haifar ko kuma yanayin da ba da kula.
Akwai wurare da suke zaba masu kirki da yawa daga babu saboda aiki, siffar, da kuma aiki. Wasu misalai na sun hada da:
Fuses: Waɗannan su ne wurare da suke hukuma circuit idan high current ta faruwar da su saboda short circuit ko overload. Sun hada da metal strip ko wire wanda ya goma yau idan an haife da fault current. Fuses su ne wurare da suke hukuma, kawai, da kuma amanna da suke bayyana saboda short-circuits. Amma, suna da wasu disadvantages, kamar:
Sun ba da aiki da ba suka sake faruwar da su ba da aiki.
Ba su ba da aiki saboda overloads ko under-voltages.
Ba su ba da indication ko isolation of the fault location.
Circuit breakers: Waɗannan su ne wurare da suke hukuma circuit idan high current ta faruwar da su saboda short circuit ko overload. Sun hada da pair of contacts wanda suke bukata ko kuma kara aiki da electromechanical mechanism wanda an fitowa da sensing element. Circuit breakers su ne wurare da suke hukuma da suke hukuma waɗannan:
Reusability and resetability after each operation.
Protection against overloads and under-voltages by adjusting their trip settings.
Indication and isolation of the fault location by manual or automatic operation.
Overload relays: Waɗannan su ne wurare da suke hukuma circuit idan high current ta faruwar da su saboda overload. Sun hada da sensing element wanda suke duba current da contact wanda suke bukata ko kuma kara aiki da electromechanical ko electronic mechanism. Overload relays su ne wurare da suke hukuma masu kirki saboda overheating da insulation damage saboda prolonged overloads ko unbalanced voltages. Akwai biyu na main types of overload relays:
Faster response and better protection against short-circuit currents or ground faults.
Immunity to ambient temperature and no need for adjustment.
Higher accuracy and repeatability due to digital processing.
Additional features such as phase loss detection, reverse rotation detection, communication, and diagnostics.
They are slow to respond and may not protect against short-circuit currents or ground faults.
They are affected by ambient temperature and may need to be adjusted accordingly.
They have limited accuracy and repeatability due to mechanical wear and tear.
Thermal overload relays: Waɗannan su ne wurare da suke amfani da bimetallic strip ko heating element don suke duba temperature rise na motor current. Idan current ta goma ƙarin da preset value, thermal element ya goma bend ko kuma melt, wanda ya ba contact ya bukata ko kuma kara aiki. Thermal overload relays su ne wurare da suke hukuma, kawai, da kuma amanna da suke bayyana saboda inverse time protection, meaning they trip faster for higher overloads. Amma, suna da wasu disadvantages, kamar:
Electronic or digital overload relays: Waɗannan su ne wurare da suke amfani da current transformer ko shunt resistor don suke duba motor current da microprocessor ko solid-state circuit don suke hukuma contact. Idan current ta goma ƙarin da preset value, electronic element ya ba signal don bukata ko kuma kara aiki. Electronic or digital overload relays su ne wurare da suke hukuma da suke hukuma waɗannan:
Differential protection relays: Waɗannan su ne wurare da suke koyar current da input da output terminals na kirki ko winding. Idan farkon da current ta goma ƙarin da wani value, indicating a winding fault, relay ya hukuma circuit. Differential protection relays su ne wurare da suke hukuma da suke hukuma waɗannan:
Reverse rotation protection relays: Waɗannan su ne wurare da suke duba direction of rotation na kirki da suke hukuma saboda running in reverse. Reverse rotation zai iya ba da lafiya ga kirki ko kuma load, musamman a cikin applications kamar conveyor belts, pumps, ko fans. Reverse rotation protection relays zai iya amfani da methods da suke duba rotation direction, kamar:
Phase sequence detection: Wannan method ya amfani da voltage relay ko wattmeter relay don suke duba phase sequence na supply voltage. Idan phase sequence ta goma yau, indicating reverse rotation, relay ya hukuma circuit.
Negative sequence detection: Wannan method ya amfani da current relay ko power relay don suke duba negative sequence component na motor current. Idan negative sequence component ta goma ƙarin, indicating reverse rotation, relay ya hukuma circuit.
Speed detection: Wannan method ya amfani da speed sensor ko tachometer don suke duba speed na motor shaft. Idan speed ta goma negative, indicating reverse rotation, relay ya hukuma circuit.
Yadda A Zaba Wurare Da Suke Zaba Masu Kirki?
Zaban wurare da suke zaba masu kirki ya ƙunshi wasu factors, kamar:
Type and size of the motor
Characteristics and ratings of the motor
Type and severity of possible faults
Requirements of the NEC and other standards
Cost and availability of the devices
NEC Article 430 provides general rules and guidelines for selecting motor protection devices based on these factors. However, it is also important to consult with the manufacturer’s recommendations and specifications for each motor and device.
Wasu general steps for selecting motor protection devices are:
Determine the full-load current (FLC) of the motor from its nameplate or from NEC Table 430.250 for AC motors or Table 430.251(B) for DC motors.
Select an overload protection device that can handle at least 115% of the FLC for motors with a service factor of 1.15 or higher or with a temperature rise of 40°C or less; or 125% of the FLC for other motors. The overload protection device can be a thermal overload relay, an electronic or digital overload relay, or a differential protection relay, depending on the type and size of the motor.
Select a short-circuit and ground-fault protection device that can handle at least 150% of the FLC for motors with a service factor of 1.15 or higher or with a temperature rise of 40°C or less; or 175% of the FLC for other motors. The short-circuit and ground-fault protection device can be a fuse or a circuit breaker, depending on the type and size of the motor.
Select a reverse rotation protection device if the motor or the load cannot tolerate reverse rotation. The reverse rotation protection device can be a phase sequence detection relay, a negative sequence detection relay, or a speed detection relay, depending on the type and size of the motor.
Select the conductor sizes for the motor circuit according to NEC Table 310.15(B)(16) for general wiring and NEC Table 430.250 for motor branch circuits. The conductors should have an ampacity not less than 125% of the FLC for motors with a service factor of 1.15 or higher or with a temperature rise of 40°C or less; or 115% of the FLC for other motors.
Select the appropriate devices and methods for motor control, starting, stopping, speed regulation, and communication according to the type and application of the motor.
结论
Motor protection is a vital aspect of electrical engineering that ensures the safety and efficiency of electric motors and their circuits. Motor protection devices are selected based on the type and size of the motor, the type and severity of possible faults, the requirements of the NEC and other standards, and the cost and availability of the devices. Motor protection devices include fuses, circuit breakers, overload relays, differential protection relays, and reverse rotation protection relays. Motor protection devices monitor and control parameters such as current, voltage, temperature, speed, and torque to prevent or minimize damage to the motor and its circuit in case of a fault or abnormal condition.
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