{"id":718,"date":"2026-06-01T09:01:04","date_gmt":"2026-06-01T09:01:04","guid":{"rendered":"https:\/\/planetary-gearboxes.com\/?p=718"},"modified":"2026-06-01T09:01:04","modified_gmt":"2026-06-01T09:01:04","slug":"planetary-gearbox-efficiency-calculation-guide","status":"publish","type":"post","link":"https:\/\/planetary-gearboxes.com\/sv\/planetary-gearbox-efficiency-calculation-guide\/","title":{"rendered":"Planetv\u00e4xell\u00e5dors verkningsgrad \u2013 ber\u00e4kning, f\u00f6rlustmekanismer och avkastning p\u00e5 investeringen"},"content":{"rendered":"
<\/p>\n Every Korean factory energy audit lists gearbox drive systems as the third-largest controllable electrical load after HVAC and lighting. A planetary gearbox at 97% efficiency and a worm reducer at 60% efficiency driving the same conveyor consume vastly different amounts of electricity over a three-shift production year<\/strong> \u2014 yet most Korean procurement decisions compare gearbox unit price without calculating the energy cost difference that accumulates over the machine’s lifetime.<\/p>\n Visa EP-BPG energisparande serie \u2192 <\/p>\n Planetary gearbox efficiency is not a single number \u2014 it is the product of three independent loss mechanisms that each respond differently to load, speed, and temperature. Understanding each mechanism separately allows Korean engineers to predict efficiency under actual operating conditions rather than relying on the catalogue’s rated-load value, which may overstate efficiency at the partial loads that dominate real production cycles.<\/p>\n Generated at each tooth contact point from the combination of rolling and sliding motion. Power loss \u221d transmitted torque \u00d7 mesh friction coefficient \u00d7 sliding velocity. The planetary arrangement distributes load across N planet contacts simultaneously, reducing the load per mesh contact and thus the friction loss per contact compared to a parallel-shaft gear of the same output torque \u2014 one key reason planetary efficiency exceeds that of worm or helical single-mesh reducers at equivalent ratios.<\/p>\n Generated at the contact between bearing rolling elements and raceways. Bearing loss has two components: a load-dependent term (proportional to transmitted radial\/axial force) and a speed-dependent viscous drag term (proportional to speed\u00b2 at high speeds). At typical servo output speeds (50\u2013300 rpm), the load-dependent term dominates. Planet carrier bearing losses are the largest single contributor to total bearing loss in a planetary stage because the planet bearings carry both the planet’s own weight and the gear mesh reaction force.<\/p>\n Sealed grease gearboxes incur two sources of no-load (speed-dependent, load-independent) losses. Grease churning occurs when rotating components displace lubricant, generating viscous drag proportional to speed and grease viscosity. Shaft seal lip drag adds a small constant frictional torque that is independent of both load and speed. Together these “spin losses” are small at normal temperatures but become significant at cold start when grease viscosity is high \u2014 explaining why measured efficiency at cold start is lower than steady-state efficiency.<\/p>\n TOTAL EFFICIENCY \u2014 COMBINING ALL THREE MECHANISMS<\/p>\n For a two-stage gearbox: Typical single-stage EP-AB at rated load, 25\u00b0C: Two-stage EP-AB at rated load: Published catalogue value: “\u226595%” \u2192 consistent \u2713 <\/p>\n The rated efficiency stated in a Korea Ever-Power EP catalogue \u2014 typically \u226595% for two-stage, \u226597% for single-stage \u2014 is measured at 100% of rated torque. In Korean production applications, gearboxes rarely run at 100% load continuously. A packaging machine servo that averages 40% of rated torque across its duty cycle operates on the efficiency curve at a point well below the catalogue peak. Understanding this partial-load efficiency drop is critical for accurate energy cost calculations.<\/p>\n The mechanism is straightforward: at partial load, gear mesh friction loss decreases proportionally with torque (less force, less friction), but grease churning and seal drag remain constant. These spin losses, which are negligible as a fraction of rated power, become a significant fraction of the reduced transmitted power. The result is a characteristic efficiency-load curve that droops at light load.<\/p>\n
<\/p>\nPlanetary Gearbox Efficiency \u2014
\nCalculation, Loss Mechanisms, and Korean Energy ROI<\/h1>\n
\n<\/a><\/p>\n<\/div>\n<\/section>\nThree Loss Mechanisms \u2014 Where Planetary Gearbox Power Goes<\/h2>\n
\u2460 Gear mesh friction loss<\/h3>\n
\nTypical mesh loss per stage: 0.5\u20131.5%
\nTwo-stage total mesh loss: 1.0\u20133.0%
\nDominant at high load, moderate speed<\/div>\n<\/div>\n\u2461 Rolling bearing friction loss<\/h3>\n
\nf\u2080, f\u2081 = bearing-type constants
\nTypical bearing loss: 0.3\u20130.8% per stage
\nIncreases with speed\u00b2 at high input RPM<\/div>\n<\/div>\n\u2462 Grease churning and seal drag loss<\/h3>\n
\nP_seal = T_seal_drag \u00d7 \u03c9 (constant torque)
\nTypical spin loss: 0.1\u20130.3%
\nDominant at low load, cold temperatures<\/div>\n<\/div>\n<\/div>\n
\n\u03b7_total = \u03b7_stage1 \u00d7 \u03b7_stage2 \u00d7 \u03b7_seals<\/p>\n
\nP_mesh \u2248 1.0%, P_bearing \u2248 0.6%, P_churn \u2248 0.2%
\n\u03b7_stage \u2248 1 \u2212 0.018 = 98.2%<\/span><\/p>\n
\n\u03b7_total \u2248 0.982 \u00d7 0.982 \u00d7 0.997 = 96.1%<\/span><\/p>\n
\nAt 30% load (partial-load condition):
\nP_mesh drops proportionally, P_churn stays constant
\n\u03b7_total \u2248 92\u201394%<\/span> (spin losses now dominate)<\/div>\n<\/div>\n<\/section>\nEfficiency vs Load Ratio \u2014 Why Partial Load Drops Planetary Gearbox Efficiency<\/h2>\n