{"id":264,"date":"2026-07-10T06:04:44","date_gmt":"2026-07-10T06:04:44","guid":{"rendered":"https:\/\/industrialelectricmotor.net\/?p=264"},"modified":"2026-07-10T06:04:44","modified_gmt":"2026-07-10T06:04:44","slug":"three-phase-motor-for-centrifugal-pump","status":"publish","type":"post","link":"https:\/\/industrialelectricmotor.net\/ko\/three-phase-motor-for-centrifugal-pump\/","title":{"rendered":"Three-Phase Motor for Centrifugal Pump"},"content":{"rendered":"
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Korea Ever-Power \u00b7 Y2 Series \u00b7 Pump Drive Application Guide<\/span><\/p>\n

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Three-Phase Motor for Centrifugal Pump:
\nSizing, Starting and Duty Cycle Guide<\/span><\/h1>\n

Centrifugal pump drives are the most energy-intensive motor application in most industrial facilities, accounting for 25 to 40 percent of total motor electricity consumption. Selecting the correct three-phase motor \u2014 matched to the pump curve, starting method, duty classification, and installation environment \u2014 is the foundation of an energy-efficient pump system. This guide covers the full motor selection process for centrifugal pump drives using the Korea Ever-Power Y2 series.<\/p>\n

Affinity Laws<\/span>
\nDOL vs Soft-Start<\/span>
\nS1 Continuous Duty<\/span>
\nIE3 Energy Saving<\/span>
\nIP54 Pump Room<\/span><\/div>\n<\/div>\n<\/div>\n

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25\u201340%<\/div>\n
Motor electricity used by pumps in industry<\/div>\n<\/div>\n
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P \u221d n\u00b3<\/div>\n
Power vs speed: cubic affinity law<\/div>\n<\/div>\n
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S1<\/div>\n
Continuous duty classification for most pumps<\/div>\n<\/div>\n
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IE3<\/div>\n
Required efficiency for Y2 pump drive motors<\/div>\n<\/div>\n
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Direct couple<\/div>\n
Flexible coupling: no gearbox for most pumps<\/div>\n<\/div>\n<\/div>\n

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\"Three-phase<\/p>\n
Centrifugal pump drives in a building services pump room \u2014 the motor and pump are directly coupled on a common baseplate, with the motor sized to the pump shaft power requirement at the design duty point on the pump curve. IE3 efficiency is critical for motors running 24\/7 in building services and process plant applications.<\/div>\n<\/div>\n

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Contents<\/div>\n
1. Affinity Laws and Pump Motor Power<\/a>
\n2. Motor Power Sizing for Pump Drives<\/a>
\n3. Starting Method: DOL, Star-Delta, Soft-Start<\/a>
\n4. Duty Classification for Pump Service<\/a>
\n5. IP Rating for Pump Environments<\/a>
\n6. Y2 Series Pump Drive Specifications<\/a>
\n7. Applications by Pump Type<\/a>
\n8. Frequently Asked Questions<\/a><\/div>\n<\/div>\n

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1. Affinity Laws and Pump Motor Power<\/h2>\n

The centrifugal pump affinity laws describe the relationship between pump speed, flow rate, head (pressure), and shaft power. These laws are fundamental to understanding why VFD speed control saves so much energy on centrifugal pump drives, and why the motor must be sized for the worst-case operating point on the pump curve rather than the average duty point.<\/p>\n

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Centrifugal Pump Affinity Laws<\/div>\n
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Flow rate (Q):<\/div>\n
Q\u2082 = Q\u2081 \u00d7 (n\u2082 \/ n\u2081)<\/div>\n
Flow is proportional to speed ratio<\/div>\n<\/div>\n
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Head (H):<\/div>\n
H\u2082 = H\u2081 \u00d7 (n\u2082 \/ n\u2081)\u00b2<\/div>\n
Head is proportional to speed squared<\/div>\n<\/div>\n
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Power (P):<\/div>\n
P\u2082 = P\u2081 \u00d7 (n\u2082 \/ n\u2081)\u00b3<\/div>\n
Power varies as CUBE of speed \u2014 80% speed = 51.2% power<\/div>\n<\/div>\n<\/div>\n<\/div>\n

The cubic power law is the reason why VFD speed control on centrifugal pumps delivers large energy savings. A pump running at 80% of rated speed delivers 80% of rated flow but consumes only 80\u00b3 = 51.2% of rated power. For a 22 kW pump motor running at 80% speed for 6,000 hours per year at $0.13\/kWh, the annual saving compared to throttle-valve control at full speed is approximately 22 \u00d7 (1\u20130.512) \u00d7 6,000 \u00d7 0.13 = $8,400 per year.<\/p>\n<\/div>\n

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2. Motor Power Sizing for Pump Drives<\/h2>\n

The motor shaft power required to drive a centrifugal pump is determined by the pump hydraulic power (flow rate \u00d7 head \u00d7 fluid density) divided by the pump hydraulic efficiency at the design duty point. Add a service factor to account for operation away from the best efficiency point (BEP) and for end-of-life impeller wear.<\/p>\n

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Pump Motor Power Formula and Example<\/div>\n
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Motor shaft power (kW):<\/div>\n
P\u2011motor = (Q \u00d7 H \u00d7 \u03c1 \u00d7 g) \u00f7 (1,000 \u00d7 \u03b7\u2011pump)<\/div>\n
Q = flow (m\u00b3\/s); H = head (m); \u03c1 = fluid density (kg\/m\u00b3); \u03b7-pump = pump efficiency (0.60\u20130.85)<\/div>\n<\/div>\n
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Worked example \u2014 water supply pump:<\/div>\n
Q = 0.05 m\u00b3\/s (180 m\u00b3\/h), H = 40 m, \u03c1 = 1,000 kg\/m\u00b3, \u03b7-pump = 0.72
\nP = (0.05 \u00d7 40 \u00d7 1,000 \u00d7 9.81) \u00f7 (1,000 \u00d7 0.72) = 27.25 kW
\nWith 1.15 service factor: 27.25 \u00d7 1.15 = 31.3 kW
\n\u2192 Select Y2 series 37 kW, 4-pole, IE3<\/strong><\/div>\n<\/div>\n<\/div>\n<\/div>\n
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Pump Application<\/th>\nTypical Pump \u03b7<\/th>\nService Factor<\/th>\nTypical Motor Range<\/th>\nY2 Pole<\/th>\n<\/tr>\n<\/thead>\n
Building water supply<\/td>\n0.65\u20130.78<\/td>\n1.10<\/td>\n0.75\u201330 kW<\/td>\n2P or 4P<\/td>\n<\/tr>\n
HVAC chilled water<\/td>\n0.70\u20130.82<\/td>\n1.10\u20131.15<\/td>\n3.0\u201375 kW<\/td>\n2P or 4P<\/td>\n<\/tr>\n
Industrial process water<\/td>\n0.68\u20130.80<\/td>\n1.15<\/td>\n1.5\u201355 kW<\/td>\n2P or 4P<\/td>\n<\/tr>\n
Irrigation \/ water transfer<\/td>\n0.62\u20130.75<\/td>\n1.15<\/td>\n2.2\u201390 kW<\/td>\n2P or 4P<\/td>\n<\/tr>\n
Slurry \/ waste water pump<\/td>\n0.55\u20130.70<\/td>\n1.25<\/td>\n2.2\u201375 kW<\/td>\n4P<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n

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3. Starting Method: DOL, Star-Delta, and Soft-Start<\/h2>\n

The starting method determines how much starting current the motor draws from the supply and how much torque is available during acceleration. For centrifugal pumps, the choice is usually straightforward because the pump load at zero speed is near zero (centrifugal pumps start unloaded against a closed valve), meaning any starting method that provides sufficient torque to overcome bearing friction and accelerate the impeller will work.<\/p>\n

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DOL (Direct-on-Line)<\/div>\n

Starting current 6\u20137.5\u00d7 rated. Suitable for pump motors up to approximately 11 kW on a stiff supply where the voltage dip during starting is below 10% of rated. Above 11 kW, check with the supply authority whether DOL starting is permitted. DOL provides maximum starting torque \u2014 more than adequate for a centrifugal pump starting against a closed valve. Simple and low-cost starter; no maintenance beyond the contactor.<\/p>\n

Use for: pumps up to 11 kW on adequate supply; where starting current is not restricted<\/div>\n<\/div>\n
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Star-Delta Starting<\/div>\n

Reduces starting current to 33% of DOL value and starting torque to 33% of DOL value. Suitable for centrifugal pumps because the load torque at start is low. Requires a 6-terminal motor (standard on Y2 series) and a star-delta timer relay. The switchover from star to delta at approximately 80% of synchronous speed causes a torque and current transient \u2014 ensure discharge valve is closed or partially closed during star-delta switchover to avoid water hammer.<\/p>\n

Use for: pumps 11\u201375 kW where starting current must be limited; closed-valve start required<\/div>\n<\/div>\n
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Soft-Starter or VFD<\/div>\n

Soft-starter provides a smooth, adjustable torque ramp that eliminates both the starting current spike and the water hammer from rapid valve-open. VFD provides the same smooth start plus variable speed operation \u2014 the combination of smooth start and speed control makes the VFD-plus-YVF2-motor the preferred specification for pump systems above 7.5 kW where flow control is required. See the Korea Ever-Power YVF2 VFD pump drive article for the full VFD pump application guide.<\/p>\n

Use for: pumps above 7.5 kW where current limits apply, or where speed control is needed<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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4. Duty Classification for Pump Service<\/h2>\n

Most centrifugal pump applications fall into S1 (continuous duty) \u2014 the pump runs continuously at approximately constant load for the full working shift or 24 hours per day. This is the most demanding duty class thermally, and the Y2 nameplate power is the maximum continuous output at 40\u00b0C ambient.<\/p>\n

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S1 Continuous \u2014 Typical for Process Pumps<\/div>\n

Building water supply circulator, chilled water pump in HVAC, process cooling water, boiler feed pump, fire pump on test run, irrigation main pump. Motor runs continuously at rated load. IE3 efficiency choice has the greatest financial impact in this duty class \u2014 a 22 kW IE3 pump motor saves approximately $500 to $900 per year in electricity compared to an IE1 motor at the same duty.<\/p>\n<\/div>\n

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S3 Intermittent \u2014 Pressure Booster Pumps<\/div>\n

Pressure booster pumps in building services that start and stop based on demand signal (pressure switch or flow sensor) operate in S3 intermittent duty. The motor runs for periods of 1 to 10 minutes, then rests. At a 40% on-time duty factor, the motor can operate at up to 115% of its S1 nameplate power without exceeding thermal limits. However, frequent starting also generates heat from starting losses \u2014 confirm the motor\u2019s maximum starts per hour limit in the Y2 data sheet.<\/p>\n<\/div>\n<\/div>\n

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Fire pump motor note: fire pump motors must be selected for locked-rotor (stall) duty \u2014 the pump may be required to run against a closed valve (zero flow) at full speed for a period, which causes the pump to heat the circulating water. The motor must remain operational and not trip on overload during this condition. Korea Ever-Power Y2 series motors with Class F insulation meet the thermal requirements for fire pump service under the locked-rotor condition duration specified in EN 12845 and NFPA 20.<\/p>\n<\/div>\n<\/div>\n

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5. IP Rating for Pump Room Environments<\/h2>\n
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IP54 \u2014 Indoor Pump Room<\/div>\n

Clean to moderately dusty indoor pump rooms with ambient humidity below 90% RH, no direct water spray. Standard for building services chilled water pumps, HVAC circulating pumps, and industrial process water pumps in enclosed plant rooms. Y2 series standard specification at IP54.<\/p>\n<\/div>\n

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IP55 \u2014 Outdoor or Wash-Down Risk<\/div>\n

Outdoor pump stations exposed to rain, or indoor pump rooms subject to hose-down cleaning or water spray from pipe leaks. Water treatment plant pump stations, irrigation pump houses, and industrial process plant pump areas specify IP55. Y2 series with IP55 option or YB2 series for hazardous area outdoor installation.<\/p>\n<\/div>\n

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Ex d IP55 \u2014 Hazardous Area Pump<\/div>\n

Chemical plant, oil and gas facility, and solvent handling pump stations in Zone 1 or Zone 2 classified areas require explosion-proof motors. Korea Ever-Power YB2 series Ex d IIB T4 IP55 is the standard specification. Gas group must be matched to the specific materials in the classified area \u2014 IIA for propane\/butane, IIB for ethylene, IIC for hydrogen or acetylene.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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6. Korea Ever-Power Y2 Series for Pump Drives<\/h2>\n
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The Y2 series is the standard motor for centrifugal pump drives in the Korea Ever-Power range. For fixed-speed pump drives, the Y2 series delivers IE3 efficiency at a competitive price across the complete 0.18 to 200 kW range. Centrifugal pumps are direct-coupled to the motor shaft via a flexible coupling \u2014 no gearbox is required because the pump and motor operate at the same speed (matched at 1,450 rpm or 2,900 rpm for 4-pole and 2-pole motors at 50 Hz). The complete Y2 motor range is available in the three-phase motor product section<\/a>.<\/p>\n

For pump systems requiring variable flow control, Korea Ever-Power recommends the YVF2 inverter-duty motor paired with a VFD. The YVF2 provides IC416 forced ventilation for full rated torque at reduced speeds, Class H insulation to withstand VFD voltage spikes, and PTC thermistor protection for the most demanding pump applications. Please contact the technical team<\/a> for VFD pump drive sizing support.<\/p>\n<\/div>\n

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Y2 Series \u2014 Pump Drive Data<\/div>\n\n\n\n\n\n\n\n\n\n\n
Power range<\/td>\n0.18 \u2013 200 kW<\/td>\n<\/tr>\n
Typical poles<\/td>\n2P (2,900 rpm) or 4P (1,450 rpm)<\/td>\n<\/tr>\n
Efficiency<\/td>\nIE3 standard<\/td>\n<\/tr>\n
Protection<\/td>\nIP54 standard; IP55 option<\/td>\n<\/tr>\n
Duty<\/td>\nS1 continuous<\/td>\n<\/tr>\n
Starting torque<\/td>\n2.0\u20132.8\u00d7 rated (adequate for pump)<\/td>\n<\/tr>\n
Coupling type<\/td>\nDirect flexible coupling (no gearbox)<\/td>\n<\/tr>\n
Certification<\/td>\nCE, ISO 9001, IEC 60034<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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7. Applications by Pump Type<\/h2>\n
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Building Water Supply<\/div>\n

Pressure booster sets, domestic water supply pumps, and fire fighting jockey pumps. Y2 2-pole (2,900 rpm) motors in 0.75 to 7.5 kW range, direct-coupled to multistage vertical centrifugal pumps. S3 duty for pressure booster, S1 for primary supply. IP54 for indoor plant room.<\/p>\n<\/div>\n

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HVAC Chilled and Condenser Water<\/div>\n

Primary and secondary chilled water pump sets in central plant HVAC systems. Y2 4-pole 3.0 to 75 kW, VFD controlled for variable flow in primary-secondary or variable primary systems. YVF2 inverter-duty motors for all VFD-controlled pump drives.<\/p>\n<\/div>\n

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Industrial Process Water<\/div>\n

Cooling water circulation, heat exchanger service pumps, reactor cooling loops. Y2 4-pole 2.2 to 55 kW, S1 continuous. Where process fluid is corrosive, specify stainless pump with standard Y2 motor \u2014 the motor itself does not contact the fluid.<\/p>\n<\/div>\n

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Irrigation and Water Transfer<\/div>\n

Agricultural irrigation, water supply transfer, and reservoir filling pumps. Y2 4-pole in 5.5 to 90 kW, often operated seasonally with extended downtime \u2014 follow storage maintenance procedure. IP55 for outdoor installation. Star-delta or soft-start for long pipe runs to prevent water hammer.<\/p>\n<\/div>\n<\/div>\n

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\"Y2<\/p>\n

HVAC Pump Room<\/div>\n<\/div>\n
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\"Y2<\/p>\n

Process Pump Drive<\/div>\n<\/div>\n
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\"Korea<\/p>\n

Stock for Fast Delivery<\/div>\n<\/div>\n
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\"Korea<\/p>\n

CE and ISO Certified<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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8. Frequently Asked Questions<\/h2>\n
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Why does my pump motor overheat when running at partial flow through a throttle valve?<\/div>\n<\/div>\n
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Throttling the discharge valve to reduce flow does not reduce the power consumed by the pump motor by a proportional amount. At partially closed discharge, the pump operates at a higher head and lower efficiency than at its best efficiency point (BEP), which means the pump shaft absorbs nearly as much power as at full flow but converts more of it to heat in the fluid rather than useful pressure work. The motor therefore draws close to full-load current even at reduced flow, and can overheat if the ambient temperature is elevated or cooling airflow is restricted. The correct solution is VFD speed control \u2014 reducing pump speed to reduce flow saves energy cubically and reduces motor load proportionally rather than wasting the energy across a throttle valve.<\/p>\n<\/div>\n<\/div>\n

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Should I select a 2-pole or 4-pole motor for my centrifugal pump?<\/div>\n<\/div>\n
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The choice between 2-pole (2,900 rpm) and 4-pole (1,450 rpm) depends on the pump design and the required operating point. Most centrifugal pumps designed for building services and HVAC are optimised to operate at 2,900 rpm (2-pole) or 1,450 rpm (4-pole), and the motor pole count must match the pump design speed to achieve the specified duty point. Check the pump data sheet for rated speed \u2014 if the duty point is specified at 2,900 rpm, use a 2-pole motor; if at 1,450 rpm, use a 4-pole. Two-pole motors are more efficient per frame size but have higher bearing wear rates at 2,900 rpm compared to 4-pole at 1,450 rpm \u2014 for continuous S1 duty, the 4-pole motor typically offers longer bearing life and lower vibration.<\/p>\n<\/div>\n<\/div>\n

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How do I size the motor if the pump data sheet only gives kW at BEP and I am running at a different duty point?<\/div>\n<\/div>\n
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Read the pump shaft power (kW) at your specific duty point from the pump performance curve, not just at BEP. Pump shaft power varies across the operating range \u2014 for most centrifugal pump designs it increases to the right of BEP (toward maximum flow at low head) and may be significantly higher than at BEP. Always read the shaft power at the worst-case duty point the pump will operate at \u2014 typically the maximum flow point on the system curve \u2014 then apply the motor service factor and select the next standard Y2 kW above that value. If the pump data sheet only shows BEP data, request the full performance curves from the pump manufacturer before specifying the motor.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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Korea Ever-Power \u00b7 Y2 Series \u00b7 Centrifugal Pump Drives<\/div>\n

Need a Motor for Your Centrifugal Pump Application?<\/h2>\n

Korea Ever-Power Y2 series: IE3 efficiency, 0.18\u2013200 kW, 2-pole and 4-pole, IP54\/55. In stock for immediate delivery. Technical sizing support available from our engineering team.<\/p>\n

View Y2 Motor Range<\/a><\/p>\n<\/div>\n<\/div>\n

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

Korea Ever-Power \u00b7 Y2 Series \u00b7 Pump Drive Application Guide Three-Phase Motor for Centrifugal Pump: Sizing, Starting and Duty Cycle Guide Centrifugal pump drives are the most energy-intensive motor application in most industrial facilities, accounting for 25 to 40 percent of total motor electricity consumption. Selecting the correct three-phase motor \u2014 matched to the pump […]<\/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-264","post","type-post","status-publish","format-standard","hentry","category-industrial-electric-motor"],"_links":{"self":[{"href":"https:\/\/industrialelectricmotor.net\/ko\/wp-json\/wp\/v2\/posts\/264","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/industrialelectricmotor.net\/ko\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/industrialelectricmotor.net\/ko\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/ko\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/ko\/wp-json\/wp\/v2\/comments?post=264"}],"version-history":[{"count":1,"href":"https:\/\/industrialelectricmotor.net\/ko\/wp-json\/wp\/v2\/posts\/264\/revisions"}],"predecessor-version":[{"id":267,"href":"https:\/\/industrialelectricmotor.net\/ko\/wp-json\/wp\/v2\/posts\/264\/revisions\/267"}],"wp:attachment":[{"href":"https:\/\/industrialelectricmotor.net\/ko\/wp-json\/wp\/v2\/media?parent=264"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/ko\/wp-json\/wp\/v2\/categories?post=264"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/ko\/wp-json\/wp\/v2\/tags?post=264"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}