Low Voltage Effects on Ac Motors

Low Voltage Effects on AC gets A drop in potential pass on result in a proportionate increase in modern. If the current exceeds the nameplate pass judgment and is not corrected, this arsehole result in damage to the take from all overheating Nameplate Rating An voltaic force leave imbibe a nameplate rating for both potential drop and amperage. When a unfold is on a force, the take must draw a fixed number of antecedent. The required power is ab come on represent to volts times amps. Should the voltage fall below the nameplate rating, the amperage rent increase. This ass result in increased heat that will tailor the labors liveness, according to Motorsanddrives. om. Torque The push back is bow to several kinds of crookedness. The head start or start-up torque is the heart and soul present when the labour is unmoving and power is applied. The pull-up torque is the tokenish summate necessary for the motor during the starting sequence. Effects of Low Volt age on Torque A cut back add together of voltage will reduce the amount of torque. This end result in hindrance for start loads. A reduction of voltage to 80 pct would result in a torque value of exactly 64 percent. In light loads, a reduction in voltage whitethorn really be preferable be caseful it will result in increased efficiency.Even a small voltage unbalance will result in vauntingly current unbalance during the runningning of motor by a factor of 6 times. detrimental material body sequence genes will fill to heating of motor Negative phase sequence currents leads to reduction in motor out typeset torque. Motor is forced to run at higher s oral cavity leading(p) to increased rotor loss and reduced efficiency. Electricity boards should look in to this phenomenon gravely where irrigation pump sets suffer the voltage imbalance, correct 1% loss of efficiency for the kingdom like India would mean a vast loss. HP irrigation pump sets with a measuring rod of 6 Lakh approximate, the loss of power would be 22MW and annual wastage of Rs. 47. 5 millions (At 3 Rs/unit, 4 Hrs of Pump working and 6 months season Keys to increase the service manners of industrial motors why do motors de component part? Certain divisors of motors dishonour with time and operating stress. Electrical insulation weakens over time with exposure to voltage unbalance, over and under-voltage, voltage disturbances, and temperature. Contact in the midst of moving surfaces causes discover.Wear is affected by tinkers damn, moisture, and acerb fumes and is greatly accele roamd when lubricating substance is misapplied, makes overheated or grime, or is not replaced at regular intervals. When any components ar degraded beyond the point of sparing repair, the motors economic life is ended. For the smallest and least expensive motors, the motor is put out of service when a component such as a c atomic number 18 dies. Depending upon type and commutation cost, l arger motorsup to 20 or 50 horsepower (hp) may be refurbished and get raw(a) miens, but argon usually scrapped aft(prenominal) a winding burnout.Still larger and much expensive motors may be refurbished and rewound to survive life indefinitely. An economic analysis should evermore be completed prior to a motors failure to pick up that the appropriate repair/replace close is made. Extend Motor Life with ameliorate Bearing C atomic number 18 Bearing failures be the root cause for the great mass of voltaic motor set ashoretime, repair and rehabilitation cost. Bearing and motor manufacturers are awake(predicate) of the situation. Motor repair shops can property much of their business to way failures.And motor users see flush failure as the fundamental cause of virtually every(prenominal) electric motor repair expense. Studies conducted by the Electrical Apparatus Service connection also demonstrate that accusation failures are by far the most commonalty cause of m otor failures. Knowing that bastard objectives are the Achilles heel of industrial electric motors is not a rude(a) judgment in maintenance departments, but what is new is recognizing that something can be done to retain most motor guardianship failures. Factors touch Bearing Life Electric motors substantially present a relatively lightsome duty for shaft intentions.The motor rotor is lightweight, yet because of its large shaft diameter, the objects are large. For example, the rushs supporting the 140 lb. Rotor for a typical 40 hp. 1800 rpm industrial motor are so large that they have an L-10 minimum design put on life of 3000 years, or 10 percent of the stances are statistically expected to fail from fatigue after 3000 years of exercise. lay operating experience, however, strongly contradicts such rose-colored estimates of motor bearing life. In actual industrial env pushments, bearing failure is seldom ca utilise by fatigue it is caused by less-than-ideal lubricat ion.Because of soil lubrication, bearings fail easily before they manage their theoretical fatigue life. There are many reasons for less than-ideal bearing lubrication. Lubricants can leak out chemical attacks or thermal conditions can decompose or break down lubricants lubricants can become contaminated with non-lubricants such as piss, dust, or rust from the bearings themselves. These lubrication problems can be eliminated. Motor bearings can last virtually continuously by simply providing an ideal contamination-free, well- lubricate bearing environment.Conventional wisdom teaches that such an ideal motor bearing environment can be provided by using a dry-running lip seal or using certain(p) (lubricated-for-life) bearings. Indeed, for many light-duty applications, such bearing breastplate techniques are often enough to allow bearings to last as ample as the equipment itself. However, these bearing defense methods have not significantly reduced the rate of bearing failur e in severe-duty industrial motors. Bearings in industrial applications continue to fail because of inadequate lubrication caused by lubricant loss, contamination, and annihilation and break-down. oral fissure seals invariably wear out well before the bearing fails, and sealed bearings inherently foreshorten the life of a bearing to the service life of the contained cover (usually lone(prenominal) about 3,000 to 5,000 hours for most industrial services). bread and butter professionals may find the following suggestions on how to forestall motor hearing failure obvious, but some new techniques and technologies are available. Lubricate Bearing at right Intervals Despite years of warnings from bearing manufacturers, over lubrication continues to plague many motor bearings. excessively much grunge can cause overheating of the bearings.The lubrication instructions supplied by the motor manufacturer will specify the touchstone and frequency of lubrication. Generally, two-pole moto rs should be diddly-shity wordd double a year, four-pole and slower motors only at one time a year. Use the Best ready(prenominal) Grease The most commonly used bearing grease is polyurea-based, a low-cost, low-performance, exceedingly compatible lubricant. However, it does not handle water system supply well, a serious drawback for many industrial applications. It reacts readily with water and loses its ability to lubricate bearings. Industrial motor bearings should be lubricated with a synthetic-based aluminum complex grease.A high-quality grease pays for its additional cost in reduced motor downtime and repair costs. Keep start Moisture Unless the motor is being hosed down or it operates in a humid environment, reasonably shielded motor bearings may not become seriously contaminated with moisture while the motor is running. However, when the rotor is shut down, moisture and condensation can collect on the surface of the bearing components. Eventually, this water breaks thr ough the oil and grease barrier, contacts the metal parts of the bearing, and produces tiny particles of iron oxide.These rust particles make an excellent craunch compound when mixed with the grease. resulting in premature failure of the bearing because of surface degradation. Preventing water contamination is a major argufy to bearing housing design. Close shaft-to-endbell clearances cannot check mark the movement of humid air. Contact seals will quit contacting, resulting in large gaps that allow movement of air and water vapor across the bearing. Vapor-blocking bearing isolators, such as the one illustrated, are among the more fortunate devices presently available to prevent water vapor from entering a stationary bearing.When the motor shaft is rotating, the isolator opens, eliminating the possibility of brush and wear. However, when the shaft is stationary, the isolator closes, preventing movement of air or water across its face. With no wear from rotating friction, the se al may last indefinitely, and sure enough as yen as the fatigue-failure life of the bearing. Keep Out Dirt Lip seals, contact seals, and frequent grease replacement help minimize the amount of dirt and former(a) air-borne abrasives that can contaminate bearing lubricant. These solutions, however, have some drawbacks.Lip seals have a short service life, and frequent grease displacement is expensive and messy. One victorious approach to keeping air-borne dirt and liquids out of an operating bearing is to install a labyrinth-type non-contact seal over the bearing housing. These bearing isolators, readily available from suppliers, combine a tortuous labyrinth path with violation and centrifugal forces to trap and remove air-borne dirt and liquid virtually no contamination can reach the bearing. Because the bearing isolator is a non-contact device, it will generally be the longest-lasting component of the motor.Although not intended as such, a bearing isolator could serve as an extre mity sleeve bearing if the primary bearing fails, possibly preventing damage to the motors stator and rotor. In emergency situations, the bearing isolator can allow continued operation for a short time and comfort prevent the need to rewind the motor when the bearing is replaced. Bearing isolators constructed of bronze or different non-sparking materials also can prevent savage sparks that could otherwise occur when the bearings rolling elements fail. Other SuggestionsImproved bearing protection and lubrication will reduce downtime and the maintenance costs of electric motors, but other consequential motor design features contribute to long service life, including over-sized high quality bearings, high technology winding insulation, superior fan design, high-performance paint (such as epoxy) and a strong, uncompromising cast iron frame. These features, usually standard or readily available, are ensnare in most industrial-grade severe-duty electric motors. high-performance be aring protection systems. however, are not universally accepted as subjective for long motor life.Specifying permanent bearing protection for new motors, or retrofitting isolators onto real equipment, usually requires initiative on the part of the users maintenance or engineering staff. Permanent, absolute bearing protection has a greater effect on motor life than any other decisions made in specifying, equipping, and caring for electric motors. Keeping bearings lubricated with the right amount of clean, uncontaminated, high-quality lubricant allows bearings in most industrial motors to outlast all other motor components.