پاراستنی موتور: شکلە، ڕووداوەکان و دێوارەکان
Sisteman parastina motorê ji bo qonşiyên û xasîlên nayênan ên motoran elektrik hilbijêr in. Motor elektrik di çendîn taybetmendiyên endustriyey û serokî de piştgirî dike, ji alatan kêmtirîn derbasên biçûk hatin. Buna, dibe ku hewce ye ku hêviya wek û ewleh û bêtirîna motor û berhane ya wê bistîne.
Di vê gotar de, li gor kîjanên motoran, tiyanên parastina motoran, û yekem ji wan dikarin bi rêjiyên National Electrical Code (NEC) û taybetmendiyên motor hilbijêrin.
Pîvandeya Motor
Pîvandeya motora şertî da ku motor beşopîn bike an bigerîze. Pîvandeyên motor bi du kategorî serekan dast bikin:
Pîvandeyên derbarî: Wan pîvandeyan ne ku ji berhane ya daxwazdar û malpera motor re dest peyda din. Mînakên pîvandeyên derbarî:
Tensîyonên neheqî: Vê amade dike hêma tensîyonên tri-fase ne heqî yên bi mezinahî û angle fazi. Evê dest bi jorîyên negativî yên di motor de, ku zêdetir xazî, xweş û tevnîşên torke.
Tensîyon bi navber: Vê amade dike hêma tensîyon bi navbera navbera motora. Evê dest bi torke bi navber, jorîyên zêdetir, û xweş û tevnîşên motor.
Takîna fasan: Vê amade dike hêma takîna fasanên daxwazdar. Evê dest bi gerîla terst û tevnîşên motor û malpera wê.
Goyiye synchronizasyon: Vê amade dike hêma motor synchronî goyiya magnetîk bi feqeyên daxwazdar. Evê dest bi slipê zêdetir, hunting, û nestandina motor.
Pîvandeyên navendî: Wan pîvandeyan ne ku ji ber motor û malpera navendî re dest peyda din. Mînakên pîvandeyên navendî:
Biheta: Vê amade dike hêma bihetên ku motor shaftê pîkerdine bi girtî, bi sekenî, û bi stres mekanîkî. Evê dest bi seda, lîna, navendî, û gerîla motor.
Xweş û tevnîş: Vê amade dike hêma demîna motor bi navbera limitên termal bi navbera overloading, bêgumanî, şertên ambient, û gerîla insulation. Evê dest bi gerîlan insulation, winding damage, û efektivîya navbera motor.
Winding failure: Vê amade dike hêma windingan motor bi short-circuit û open-circuit bi navbera gerîlan insulation, stres mekanîk, û pîvandeyên derbarî. Evê dest bi sparks, smoke, fire, û loss of torque di motor de.
Pîvandeya earth: Vê amade dike hêma phase conductor motor bi navbera parta grounded circuit û equipment. Evê dest bi fault currents bi navber, gerîlan insulation û equipment, û potential shock hazards.
Pîvandeyên motor dikarin bi navbera performans, ewleh, û omîdnameya motor û berhane ya wê. Buna, dibe ku bi rêjeyên û metodyên û devicyên ûsîn bikin.
Çi Ye Devicya Parastina Motor
Devicya parastina motora device e ku ji ber parametersên motor û berhane ya wê, wisa jor, tensîyon, dem, speed û torque monitor û kontrol bike. Amada devicya parastina motora ku ji ber pîvand û şertên abnormî parastina û minimiz bike.
Ji bo funksiyon, principle, û application, divê devicyên parastina motoran ne. Mînakên bi navber:
Fuses: Wan device ne ku ji ber jorîyên bi mezinahî di navbera circuit de bikin. Wan ji metal strip û wire bikin ku hêma bi heat bi fault current melt. Fuses simple, cheap, û reliable device ne ku fast protection against short-circuits bike. Lakin, wan bi disadvantages, wisa:
Nebi reusable û hewce ye ku bi navbera her operation replace bike.
Nebi protection against overloads û under-voltages.
Nebi indication û isolation of the fault location.
Circuit breakers: Wan device ne ku ji ber jorîyên bi mezinahî di navbera circuit de bikin. Wan ji pair of contacts bikin ku open û close by electromechanical mechanism triggered by sensing element. Circuit breakers advanced than fuses as they provide the following:
Reusability û resetability after each operation.
Protection against overloads û under-voltages by adjusting their trip settings.
Indication û isolation of the fault location by manual û automatic operation.
Overload relays: Wan device ne ku ji ber jorîyên bi mezinahî di navbera circuit de bikin. Wan ji sensing element bikin ku jor measure û contact open û close by electromechanical û electronic mechanism. Overload relays designed to protect motors from overheating û insulation damage due to prolonged overloads û unbalanced voltages. There are two main types of overload relays:
Faster response û better protection against short-circuit currents û ground faults.
Immunity to ambient temperature û no need for adjustment.
Higher accuracy û repeatability due to digital processing.
Additional features such as phase loss detection, reverse rotation detection, communication, û diagnostics.
They are slow to respond û may not protect against short-circuit currents û ground faults.
They are affected by ambient temperature û may need to be adjusted accordingly.
They have limited accuracy û repeatability due to mechanical wear û tear.
Thermal overload relays: Wan device ne ku bimetallic strip û heating element bikin ku sense the temperature rise of the motor current. Hêma jor bi preset value exceed, thermal element bend û melt, causing the contact to open û close. Thermal overload relays simple, cheap, û reliable device ne ku inverse time protection, meaning they trip faster for higher overloads. Lakin, wan bi disadvantages, wisa:
Electronic û digital overload relays: Wan device ne ku current transformer û shunt resistor bikin ku measure the motor current û microprocessor û solid-state circuit control the contact. Hêma jor bi preset value exceed, electronic element signal send to open û close the contact. Electronic û digital overload relays advanced than thermal overload relays as they provide:
Differential protection relays: Wan device ne ku compare the currents at the input û output terminals of the motor û its winding. Hêma difference between the currents exceed a certain value, indicating a winding fault, relay trips the circuit. Differential protection relays very sensitive û reliable device ne ku fast protection against phase-to-phase û phase-to-earth faults in low-voltage û high-voltage motors.
Reverse rotation protection relays: Wan device ne ku detect the direction of rotation of the motor û prevent it from running in reverse. Reverse rotation can damage the motor û the load, especially in applications such as conveyor belts, pumps, û fans. Reverse rotation protection relays can use different methods to sense the rotation direction, wisa:
Phase sequence detection: This method uses a voltage relay û wattmeter relay to measure the phase sequence of the supply voltage. If the phase sequence is reversed, indicating reverse rotation, the relay trips the circuit.
Negative sequence detection: This method uses a current relay û power relay to measure the negative sequence component of the motor current. If the negative sequence component is high, indicating reverse rotation, the relay trips the circuit.
Speed detection: This method uses a speed sensor û tachometer to measure the speed of the motor shaft. If the speed is negative, indicating reverse rotation, the relay trips the circuit.
Bi Çawa Deviceyên Parastina Motor Hilbijêrin
Hilbijartin deviceyên parastina motor depends on several factors, wisa:
Type û size of the motor
Characteristics û ratings of the motor
Type û severity of possible faults
Requirements of the NEC û other standards
Cost û availability of the devices
NEC Article 430 provides general rules û guidelines for selecting motor protection devices based on these factors. Lakin, it is also important to consult with the manufacturer’s recommendations û specifications for each motor û device.
Some general steps for selecting motor protection devices are:
Determine the full-load current (FLC) of the motor from its nameplate û from NEC Table 430.250 for AC motors û 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 û with a temperature rise of 40°C or less; û 125% of the FLC for other motors. The overload protection device can be a thermal overload relay, an electronic û digital overload relay, û differential protection relay, depending on the type û size of the motor.
Select a short-circuit û ground-fault protection device that can handle at least 150% of the FLC for motors with a service factor of 1.15 or higher û with a temperature rise of 40°C or less; û 175% of the FLC for other motors. The short-circuit û ground-fault protection device can be a fuse û circuit breaker, depending on the type û size of the motor.
Select a reverse rotation protection device if the motor û the load cannot tolerate reverse rotation. The reverse rotation protection device can be a phase sequence detection relay, a negative sequence detection relay, û speed detection relay, depending on the type û size of the motor.
Select the conductor sizes for the motor circuit according to NEC Table 310.15(B)(16) for general wiring û 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 û with a temperature rise of 40°C or less; û 115% of the FLC for other motors.
Select the appropriate devices û methods for motor control, starting, stopping, speed regulation, û communication according to the type û application of the motor.
Perjîn
Parastina motor vital aspect of electrical engineering e ku ewleh û efektivîya motoran elektrik û berhane ya wan bistîne. Deviceyên parastina motor selected based on the type û size of the motor, the type û severity of possible faults, the requirements of the NEC û other standards, û cost û availability of the devices. Deviceyên parastina motor include fuses, circuit breakers, overload relays, differential protection relays, û reverse rotation protection relays. Deviceyên parastina motor monitor û control parameters such as current, voltage, temperature, speed, û torque to prevent û minimize damage to the motor û its circuit in case of a fault û abnormal condition.
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