{"id":170,"date":"2026-07-08T08:56:55","date_gmt":"2026-07-08T08:56:55","guid":{"rendered":"https:\/\/industrialelectricmotor.net\/?p=170"},"modified":"2026-07-08T08:56:55","modified_gmt":"2026-07-08T08:56:55","slug":"how-to-maintain-an-industrial-electric-motor","status":"publish","type":"post","link":"https:\/\/industrialelectricmotor.net\/da\/how-to-maintain-an-industrial-electric-motor\/","title":{"rendered":"How to Maintain an Industrial Electric Motor"},"content":{"rendered":"
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Korea Ever-Power \u00b7 Maintenance Guide \u00b7 IEC 60034<\/span><\/p>\n

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How to Maintain an Industrial Electric Motor:
\nComplete Maintenance Checklist<\/span><\/h1>\n

Planned electric motor maintenance extends motor service life from an average of 8 to 12 years under reactive maintenance to 20 to 30 years under a structured programme. The tasks involved are straightforward \u2014 bearing lubrication, insulation resistance measurement, current balance monitoring, and cooling system cleaning \u2014 but they must be carried out at consistent intervals based on the motor\u2019s actual operating conditions, not on a generic calendar schedule. This checklist covers everything a maintenance team needs to protect the investment in a three-phase industrial motor fleet.<\/p>\n

Daily \/ Weekly Checks<\/span>
\nMonthly Monitoring<\/span>
\nAnnual Inspection<\/span>
\nBearing Replacement<\/span>
\nInsulation Resistance<\/span><\/div>\n<\/div>\n<\/div>\n

<\/p>\n

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20\u201330 yr<\/div>\n
Service life with planned maintenance<\/div>\n<\/div>\n
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8\u201312 yr<\/div>\n
Average life under reactive maintenance<\/div>\n<\/div>\n
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44%<\/div>\n
Failures caused by bearing faults<\/div>\n<\/div>\n
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26%<\/div>\n
Failures from insulation breakdown<\/div>\n<\/div>\n
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< 1 h<\/div>\n
Time for a complete annual inspection<\/div>\n<\/div>\n<\/div>\n

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\"Electric<\/p>\n
Systematic motor inspection \u2014 bearing temperature measurement, current balance monitoring, and insulation resistance testing are the three highest-value electric motor maintenance tasks, catching 70 percent of developing faults before they cause unplanned downtime.<\/div>\n<\/div>\n

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Contents<\/div>\n
1. Why Planned Maintenance Reduces Total Cost<\/a>
\n2. Daily and Weekly Visual Checks<\/a>
\n3. Monthly Checks<\/a>
\n4. Annual Maintenance<\/a>
\n5. Bearing Replacement<\/a>
\n6. Winding Re-varnish and Rewind Decision<\/a>
\n7. Maintenance Schedule Reference<\/a>
\n8. Frequently Asked Questions<\/a><\/div>\n<\/div>\n

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1. Why Planned Maintenance Reduces Total Cost of Ownership<\/h2>\n

The total cost of owning an industrial electric motor over its service life is dominated by energy cost (typically 97 to 99 percent of total lifetime cost for continuously running motors) and failure-related costs (unplanned downtime, emergency replacement, production loss). The motor purchase price accounts for less than 2 percent of total lifetime cost in most applications.<\/p>\n

Electric motor maintenance programmes work on two distinct mechanisms. First, they extend service life by preventing the progressive damage that accumulates from contaminated bearings, degraded insulation, and blocked cooling \u2014 reducing the frequency of early failure. Second, they give maintenance teams advance warning of developing faults, allowing motors to be replaced on a planned schedule during scheduled production downtime rather than as an emergency during production hours. Emergency motor replacements typically cost 4 to 10 times more than planned replacements when production loss cost is included.<\/p>\n

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44%<\/div>\n
of motor failures stem from bearing faults \u2014 almost all preventable with correct lubrication and alignment<\/div>\n<\/div>\n
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26%<\/div>\n
from insulation breakdown \u2014 detected early by insulation resistance trending before failure<\/div>\n<\/div>\n
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21%<\/div>\n
from overloading and over-temperature \u2014 prevented by current monitoring and cooling maintenance<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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2. Daily and Weekly Visual Checks<\/h2>\n

Daily and weekly electric motor maintenance checks require no tools and no motor isolation \u2014 they are performed during normal production operation by operations or maintenance staff as part of a routine equipment walk-around. Despite their simplicity, they catch a significant proportion of developing problems before they cause a production stop.<\/p>\n

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DAILY<\/div>\n
Listen for unusual noise<\/div>\n<\/div>\n

Walk past each motor during normal operation and listen for changes from the baseline sound. Grinding or rumbling from bearings, increased humming from electrical issues, or rattling from loose fan cover or terminal box screws are all audible before they appear in any instrument reading. Log any change from normal baseline sound immediately and schedule investigation.<\/p>\n<\/div>\n

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DAILY<\/div>\n
Check frame temperature by touch<\/div>\n<\/div>\n

Briefly touch the motor frame (not the fan cover \u2014 this can be hotter than the frame) to confirm it is warm but not excessively hot. A Class F motor in normal S1 duty at 40\u00b0C ambient will have a frame surface temperature of approximately 55 to 75\u00b0C \u2014 warm to the touch but holdable for 1 to 2 seconds. A frame too hot to touch briefly (above approximately 80\u00b0C surface) indicates overloading, blocked cooling, or elevated ambient temperature requiring investigation.<\/p>\n<\/div>\n

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WEEKLY<\/div>\n
Visual inspection of motor and mounting<\/div>\n<\/div>\n

Check for: visible grease or oil leakage around the shaft seal (indicates seal wear); corrosion on frame, end shields, or fasteners (indicates moisture ingress or chemical exposure requiring immediate investigation in food and chemical plant areas); dust or debris accumulation on cooling fins restricting airflow; loose or missing hold-down bolt nuts; coupling guard in place and secure; terminal box cover sealed and screws tight.<\/p>\n<\/div>\n

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WEEKLY<\/div>\n
Check for vibration by touch<\/div>\n<\/div>\n

Briefly place a hand flat on the motor frame while it is running. Normal vibration should be barely perceptible. Vibration clearly felt by touch, or vibration visible in the mounting structure, indicates a developing mechanical issue \u2014 misalignment, unbalanced load, or bearing deterioration. Log the observation and schedule a formal vibration measurement at the next available opportunity.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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3. Monthly Checks: Current, Vibration, and Temperature<\/h2>\n

\"Electric<\/p>\n

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Phase Current Measurement<\/div>\n

Measure all three phase currents with a clamp meter under the motor\u2019s normal operating load. Record the values and compare with the nameplate full-load current and with previous monthly readings. Acceptable current balance: all three phases within 5 percent of each other. Current above nameplate indicates overload. A current imbalance above 5 percent indicates supply voltage imbalance or a developing winding fault and requires further investigation. Trending current readings over successive months reveals progressive changes before they reach fault level.<\/p>\n

Record: I-L1, I-L2, I-L3 (A); date and load condition; compare with previous reading<\/div>\n<\/div>\n
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Bearing Temperature<\/div>\n

Measure the bearing housing temperature at both drive-end and non-drive-end bearing positions using a contact or infrared thermometer. Compare with the baseline temperature established during commissioning. A bearing temperature rise of 10 K above the established baseline at the same ambient temperature and load indicates developing bearing deterioration (contamination, loss of lubrication, or beginning of fatigue). Bearing temperature above 90\u00b0C at the housing surface requires immediate investigation regardless of the trend.<\/p>\n

Normal range: frame ambient + 15\u201335 K. Alert: more than 10 K above established baseline<\/div>\n<\/div>\n
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Vibration Velocity<\/div>\n

Measure vibration velocity (mm\/s RMS) at the bearing housing in three axes: horizontal, vertical, and axial. Compare with IEC 60034-14 Grade A limit of 2.8 mm\/s RMS for standard motors in frames 56 to 400. Levels above 4.5 mm\/s indicate a developing problem requiring investigation. Trending vibration over successive months reveals alignment deterioration, foundation loosening, or bearing wear progression. Monthly vibration trending is the most effective condition monitoring technique for early fault detection in electric motor installations.<\/p>\n

IEC limit: 2.8 mm\/s RMS. Investigate above 4.5 mm\/s. Trend monthly for progression<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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4. Annual Maintenance: Insulation, Bearings, Terminals<\/h2>\n

Annual electric motor maintenance requires a planned shutdown period \u2014 typically during scheduled plant maintenance or equipment overhaul intervals. The motor should be isolated, locked out, and allowed to cool before any work begins. The following tasks should be completed at every annual maintenance interval:<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n\n
Task<\/th>\nMethod<\/th>\nAcceptance Criterion<\/th>\nAction If Failed<\/th>\n<\/tr>\n<\/thead>\n
Insulation resistance test<\/td>\n500 V DC megohmmeter, phase-to-earth<\/td>\n\u2265 1 M\u03a9 at 20\u00b0C<\/td>\nDry out; retest. If still low, inspect and rewind.<\/td>\n<\/tr>\n
Winding resistance balance<\/td>\nMilliohmmeter on each phase<\/td>\nAll phases within \u00b12%<\/td>\nInvestigate for turn-to-turn short or open circuit.<\/td>\n<\/tr>\n
Cooling fin cleaning<\/td>\nCompressed air or vacuum<\/td>\nAll passages clear of debris<\/td>\nManual cleaning with brush if debris is packed.<\/td>\n<\/tr>\n
Terminal tightness check<\/td>\nTorque wrench to IEC 60999 spec<\/td>\nNo looseness; no discolouration<\/td>\nRe-torque; replace discoloured terminals.<\/td>\n<\/tr>\n
Bearing assessment<\/td>\nListen and feel for roughness; check grease<\/td>\nSmooth rotation; fresh grease<\/td>\nRegrease if due; replace if rough.<\/td>\n<\/tr>\n
Earth continuity check<\/td>\nLow-resistance ohmmeter, frame to PE<\/td>\n< 0.5 \u03a9 frame to PE terminal<\/td>\nCheck earth lead and connection; clean contact point.<\/td>\n<\/tr>\n
Alignment re-check<\/td>\nDial indicator or laser alignment<\/td>\nWithin coupling manufacturer spec<\/td>\nRe-align with shims; check foundation bolts.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n

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5. Bearing Replacement Intervals and Procedure<\/h2>\n
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Bearings are the primary wear component in squirrel-cage AC induction motors. Bearing selection and replacement intervals depend on the operating speed, radial load, ambient temperature, and lubrication condition. Korea Ever-Power Y2 series motors in frames up to 160L use sealed-for-life deep-groove ball bearings that require no regreasing and should be replaced at the intervals below. Frame sizes 180M and above use re-greasable bearings with grease nipples.<\/p>\n

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Bearing Replacement Intervals<\/div>\n\n\n\n\n\n\n\n\n\n
Operating Condition<\/th>\nReplace At<\/th>\n<\/tr>\n<\/thead>\n
Normal load, 40\u00b0C ambient, continuous<\/td>\n20,000\u201330,000 h<\/td>\n<\/tr>\n
High radial load (belt or chain drive)<\/td>\n10,000\u201315,000 h<\/td>\n<\/tr>\n
High ambient temperature (>50\u00b0C)<\/td>\n10,000\u201320,000 h<\/td>\n<\/tr>\n
Frequent starts \/ stops (>60\/hour)<\/td>\n8,000\u201312,000 h<\/td>\n<\/tr>\n
VFD-driven (bearing current risk)<\/td>\n5,000\u201310,000 h without protection<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n
\"Korea<\/p>\n
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Bearing replacement note: always replace both DE and NDE bearings at the same time, even if only one shows signs of wear. Mixing a new bearing with a worn one creates unequal radial stiffness and will accelerate wear on the new bearing. Use only bearings of the exact specification shown on the motor data plate or Korea Ever-Power spare parts list.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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Regreasing Procedure (Frame 180 and Above)<\/div>\n
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Grease type:<\/strong> Lithium-based NLGI 2\/3, or as specified on the motor nameplate. Never mix grease types \u2014 different thickener chemistries can react and liquefy, losing all lubrication value.<\/div>\n
Quantity:<\/strong> Add only the specified grease quantity (stated on nameplate or in data sheet). Overgreasing forces lubricant into the motor through the inner seal, contaminating the winding.<\/div>\n
Method:<\/strong> Clean the grease nipple with a rag before attaching the grease gun. Add grease slowly with the motor running so excess grease can escape through the relief plug. Run for 30 minutes after regreasing before replacing the relief plug.<\/div>\n
Interval:<\/strong> As stated on the motor nameplate, typically every 4,000 to 8,000 hours for 4-pole motors at 40\u00b0C ambient and normal radial load. Reduce by 50% for motors running above 60\u00b0C ambient or with high radial load.<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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6. Winding Re-varnish and Rewind Decision Criteria<\/h2>\n

When an annual insulation resistance test returns a value below 1 M\u03a9 after the motor has been fully dried, or when visual inspection reveals carbonised winding insulation or cracked coil sections, the motor winding requires either re-varnishing (if only surface contamination has occurred) or a full rewind.<\/p>\n

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Re-varnish (VPI treatment)<\/div>\n

Vacuum pressure impregnation (VPI) with polyester or epoxy resin is appropriate when: insulation resistance is below 1 M\u03a9 due to surface moisture absorption or light contamination (the winding structure is mechanically intact); visual inspection shows no charred, cracked, or physically damaged coil sections; and the winding resistance balance is within \u00b12% (indicating no turn-to-turn short circuits). VPI restores surface insulation integrity and typically recovers insulation resistance to above 100 M\u03a9 on a clean, mechanically intact winding.<\/p>\n<\/div>\n

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Full Rewind Decision<\/div>\n

A full rewind is required when: winding resistance is unbalanced by more than 2% between phases (turn-to-turn short circuit confirmed); there is visible charring, carbonisation, or physical damage to coil sections; insulation resistance remains below 1 M\u03a9 after thorough drying and VPI treatment; or the motor has failed electrically (phase-to-phase or phase-to-earth short circuit). For motors below 11 kW, compare rewind cost against the price of a new Korea Ever-Power Y2 series replacement \u2014 new motor replacement is often more cost-effective below this power level.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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7. Electric Motor Maintenance Schedule Reference<\/h2>\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Task<\/th>\nDaily<\/th>\nWeekly<\/th>\nMonthly<\/th>\nAnnual<\/th>\nPer Hours<\/th>\n<\/tr>\n<\/thead>\n
Sound \/ noise check<\/td>\n\u2713<\/td>\n<\/td>\n<\/td>\n<\/td>\n\u2014<\/td>\n<\/tr>\n
Frame temperature touch check<\/td>\n\u2713<\/td>\n<\/td>\n<\/td>\n<\/td>\n\u2014<\/td>\n<\/tr>\n
Visual inspection, vibration by touch<\/td>\n<\/td>\n\u2713<\/td>\n<\/td>\n<\/td>\n\u2014<\/td>\n<\/tr>\n
Phase current measurement (all 3 phases)<\/td>\n<\/td>\n<\/td>\n\u2713<\/td>\n<\/td>\n\u2014<\/td>\n<\/tr>\n
Bearing temperature (infrared \/ contact)<\/td>\n<\/td>\n<\/td>\n\u2713<\/td>\n<\/td>\n\u2014<\/td>\n<\/tr>\n
Vibration velocity measurement<\/td>\n<\/td>\n<\/td>\n\u2713<\/td>\n<\/td>\n\u2014<\/td>\n<\/tr>\n
Insulation resistance measurement<\/td>\n<\/td>\n<\/td>\n<\/td>\n\u2713<\/td>\n\u2014<\/td>\n<\/tr>\n
Winding resistance balance<\/td>\n<\/td>\n<\/td>\n<\/td>\n\u2713<\/td>\n\u2014<\/td>\n<\/tr>\n
Terminal tightness and cooling fin cleaning<\/td>\n<\/td>\n<\/td>\n<\/td>\n\u2713<\/td>\n\u2014<\/td>\n<\/tr>\n
Alignment re-check<\/td>\n<\/td>\n<\/td>\n<\/td>\n\u2713<\/td>\n\u2014<\/td>\n<\/tr>\n
Bearing regreasing (frame 180 and above)<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n4,000\u20138,000 h<\/td>\n<\/tr>\n
Bearing replacement (frame up to 160L)<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n20,000\u201330,000 h<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n

<\/p>\n

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\"Industrial<\/p>\n

Mining Conveyor Drives<\/div>\n<\/div>\n
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\"Korea<\/p>\n

Engineering Support<\/div>\n<\/div>\n
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\"Korea<\/p>\n

Ready Spare Parts Stock<\/div>\n<\/div>\n
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\"Korea<\/p>\n

Fast Global Delivery<\/div>\n<\/div>\n<\/div>\n

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8. Frequently Asked Questions<\/h2>\n
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How does ambient temperature above 40\u00b0C affect the electric motor maintenance schedule?<\/div>\n<\/div>\n
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Elevated ambient temperature accelerates insulation degradation, bearing lubricant oxidation, and corrosion. For every 10 K rise in ambient temperature above 40\u00b0C, insulation life halves (the Montsinger Rule), and bearing regreasing intervals should be reduced by approximately 30 to 40 percent. At 50\u00b0C ambient, schedule insulation resistance tests every 6 months rather than annually. At 60\u00b0C ambient, monthly insulation resistance testing is advisable for critical motors. For Korea Ever-Power Y2 series motors at ambient above 40\u00b0C, the motor must be derated in output power per IEC 60034-1: approximately 1 percent derating per degree above 40\u00b0C. Consult the Korea Ever-Power engineering team for specific derating guidance for your installation ambient temperature.<\/p>\n<\/div>\n<\/div>\n

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What records should be kept as part of an electric motor maintenance programme?<\/div>\n<\/div>\n
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A minimum motor maintenance record for each motor in the fleet should contain: motor identification (serial number, frame size, location, driven equipment); commissioning data (insulation resistance at installation, vibration baseline, alignment readings, overload relay setting); and a dated maintenance log recording every measurement, observation, and intervention. The maintenance log should record the actual measured values \u2014 not just pass\/fail \u2014 because trending the values over time (insulation resistance declining from 500 M\u03a9 at commissioning to 50 M\u03a9 at year 3 to 8 M\u03a9 at year 5 to 1.2 M\u03a9 at year 6) reveals developing problems far earlier than a pass\/fail threshold check. Korea Ever-Power recommends a simple spreadsheet maintenance log for facilities without a CMMS (computerised maintenance management system).<\/p>\n<\/div>\n<\/div>\n

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Can spare motors be stored long-term and what maintenance do they require in storage?<\/div>\n<\/div>\n
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Korea Ever-Power Y2 series motors can be stored for up to 2 years in a clean, dry, vibration-free indoor environment without significant degradation if the following precautions are taken: store the motor on a flat surface with the shaft horizontal to prevent bearing brinelling from long-term static load in one position; rotate the shaft manually by hand at least once per month to redistribute bearing grease and prevent false brinelling from micro-vibration; check and record insulation resistance every 6 months in storage; if insulation resistance falls below 10 M\u03a9, run the motor at no-load for 30 to 60 minutes to drive off moisture. For storage longer than 2 years, replace bearings before commissioning regardless of storage condition, as static bearing grease oxidation and fretting corrosion under no-load may have progressed beyond the lubricant service life.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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Korea Ever-Power \u00b7 Motor Replacement and Spares<\/div>\n

Need Replacement Motors or Maintenance Support?<\/h2>\n

Korea Ever-Power holds stock of Y2, YB2, Y2EJ, YVF2, and BXG series motors across all standard IEC frames for planned and emergency replacement. Technical maintenance guidance available from our engineering team.<\/p>\n

View Motor Range<\/a><\/p>\n<\/div>\n<\/div>\n

Edited by Cxm<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

Korea Ever-Power \u00b7 Maintenance Guide \u00b7 IEC 60034 How to Maintain an Industrial Electric Motor: Complete Maintenance Checklist Planned electric motor maintenance extends motor service life from an average of 8 to 12 years under reactive maintenance to 20 to 30 years under a structured programme. The tasks involved are straightforward \u2014 bearing lubrication, insulation […]<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[28],"tags":[],"class_list":["post-170","post","type-post","status-publish","format-standard","hentry","category-industrial-electric-motor"],"_links":{"self":[{"href":"https:\/\/industrialelectricmotor.net\/da\/wp-json\/wp\/v2\/posts\/170","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/industrialelectricmotor.net\/da\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/industrialelectricmotor.net\/da\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/da\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/da\/wp-json\/wp\/v2\/comments?post=170"}],"version-history":[{"count":1,"href":"https:\/\/industrialelectricmotor.net\/da\/wp-json\/wp\/v2\/posts\/170\/revisions"}],"predecessor-version":[{"id":173,"href":"https:\/\/industrialelectricmotor.net\/da\/wp-json\/wp\/v2\/posts\/170\/revisions\/173"}],"wp:attachment":[{"href":"https:\/\/industrialelectricmotor.net\/da\/wp-json\/wp\/v2\/media?parent=170"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/da\/wp-json\/wp\/v2\/categories?post=170"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/da\/wp-json\/wp\/v2\/tags?post=170"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}