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လွ်ပ္စစ္ေမာ္တာ၏ စြမ္းအင္ဆံုးရွဳံးမွဳမ်ား Motor Losses

 

 

လွ်ပ္စစ္ေမာ္တာသည္ လွ်ပ္စစ္စြမ္းအင္ (electrical energy input)မွ စက္မွဳစြမ္းအင္(mechanical energy output)သုိ့ေၿပာင္းေပးသည္ ့ ကိရိယာတစ္မ်ိဳးၿဖစ္သည္။ ေမာ္တာ၏ Efficiency သည္ စက္မွဳစြမ္းအင္(mechanical energy output) ကို လွ်ပ္စစ္စြမ္းအင္ (electrical energy input) ႏွင့္စားထားသည့္အခ်ိဳးၿဖစ္သည္။

 

စြမ္းအင္တည္ၿမဲမွဳနိယာမအရ

 လွ်ပ္စစ္စြမ္းအင္ (electrical energy input) = စက္မွဳစြမ္းအင္(mechanical energy output) + ဆံုးရွံဳးမွဴမ်ား(losses)

 ေမာ္တာ၏ losses မ်ားေလေလ Efficiency နည္းေလေလၿဖစ္သည္။

 

 

Copper loss    

Copper losses ဆိုသည္မွာ ေမာ္တာ၏ Rotor ႏွင့္ Stator မ်ားတြင္ရွိေသာ ေၾကးနီ(Copper) ဝိုင္ယာမ်ားအတြင္းတြင္ လွ်ပ္စစ္စီးဆင္းမွဳေၾကာင့္ၿဖစ္ေပၚလာေသာ losses ၿဖစ္သည္။ ေၾကးနီ(Copper) ဝိုင္ယာမ်ား သည္ ေမာ္တာ၏ Rotor ႏွင့္ Stator ႏွစ္ခုစလံုးတြင္ရွိေသာေၾကာင့္ Rotor ေရာ Stator တြင္ပါ Copper losses ၿဖစ္ေပၚသည္။

Stator winding ႏွင့္ Rotor winding တုိ့ ၏ Resistance ေၾကာင့္ၿဖစ္သည္။

 

Stator ႏွင့္ Rotor winding အတြင္းတြင္ current ၿဖတ္စီးၿခင္းေၾကာင့္ Stator Copper losses ၿဖစ္ေပၚလာသည္။ ထုိ Losses ၿဖစ္သည့္ပမာဏမွာ ၿဖတ္စီး သည့္ current ႏွစ္ထပ္ကိန္းႏွင့္ Resistance တုိ့ေၿမွာ္ၿခင္း ၿဖစ္သည္။

Losses = Current(I) x Current(I) x Resistance

 

ထုိ လွ်ပ္စစ္စြမ္းအင္မ်ားသည္ မလုိလားအပ္သည့္ အပူ(heat)အၿဖစ္သုိ့ ေၿပာင္းလဲသြားၿပီး စြမ္းအင္ဆံုးရွဳံးမွဳၿဖစ္ေပၚသည္။

ထိုေၾကာင့္ေမာ္တာသည္ လုိအပ္သည္ထက္ပိုပူေလေလ စြမ္းအင္ဆံုးရွံဳးမွဳမ်ားေလေလၿဖစ္သည္။

 

 

Copper loss ေၾကာင့္ၿဖစ္ေသာ စြမ္းအင္ဆံုးရွဳံးမွဳေလ်ာ့နည္းေစရန္ Stator Slot ကို ေၿပာင္းလဲနုိင္သည္။

Stator winding တြင္းတြင္ရွိေသာ ဝုိင္ယာ၏ ထုထည္(Volume) မ်ားလာေစရန္ Insulation thickness ကုိေလွ်ာ ့ခ်နုိင္သည္။

Rotor ၏ Copper losses နည္းေစရန္ conductive bar ႏွင့္ End ring ၏ အရြယ္အစားကိုတုိးေပးနုိင္သည္။ ထုိသုိ့ တုိးေပးၿခင္းၿဖင့္ Resistance ကို ေလွ်ာ့နည္းေစနုိင္သည္။

 

Copper losses သည္ စြမ္းအင္ဆံုးရွဳံးမွဳစုစုေပါင္း (Total losses ) ၏ ၅၈%ၿဖစ္သည္။

 

 

Core losses

Core losses သည္ Eddy current losses ႏွင့္ hysteresis တုိ့ၿဖစ္သည္။

Core material (hysteresis) အား  သံလိုက္စက္ကြင္း(magnetized) ၿဖစ္ရန္အတြက္လုိအပ္ေသာ စြမ္းအင္ၿဖစ္သည္။ Core material ၌ Eddy current ၿဖစ္ေပၚရန္အတြက္ စြမ္းအင္အခ်ိဳ ့ဆံုးရွဳံးမွဳၿဖစ္ေပၚသည္။

 

 Improved permeability electromagnetic (Silicon) Steel ကို အသံုးၿပဳၿခင္းၿဖင့္ Core losses ၿဖစ္ေပၚမွဳနည္းေအာင္ၿပဳလုပ္နုိင္သည္။ Core ကို ပိုမိုရွည္လ်ားေအာင္ၿပဳလုပ္ၿခင္းၿဖင့္ magnetic flux densities သည္ ေလွ်ာ ့နည္းလာကာ Core losses ၿဖစ္ေပၚမွဳလည္းနည္းလာသည္။ Thinner Steel laminations ကုိအသံုးၿပဳၿခင္းၿဖင့္ Eddy current losses ကိုလည္းနည္းေအာင္ၿပဳလုပ္နုိင္သည္။

 

Core losses ႏွင့္ Windage losses တုိ့သည့္ ေမာ္တာ၏ ဝန္ (load)ႏွင့္မသက္ဆုိင္ေပ။ loading % မ်ားသည္ၿဖစ္ေစ၊ နည္းသည္ၿဖစ္ေစ Core losses ႏွင့္ Windage losses တုိ့မွာ မေၿပာင္းလဲေပ။

Core losses သည္ စြမ္းအင္ဆံုးရွဳံးမွဳစုစုေပါင္း (Total losses ) ၏ ၁၂%ၿဖစ္သည္။

 

 Windage and friction losses

Windage သည္ ေမာ္တာအားေအးေအာင္ (အပူခ်ိန္မတက္ေအာင္) တပ္ဆင္ထားေသာ ပန္ကာေၾကာင့္ၿဖစ္ေသာ စြမ္းအင္ဆံုးရွဳံးမွဳၿဖစ္သည္။ ပန္ကာအားဒီဇုိင္းေကာင္းေအာင္ၿပဳလုပ္ၿခင္းၿဖင့္လည္း Windage losses ကိုေလွ်ာ့နည္းေစနုိင္သည္။

Windage and friction losses  သည္ စြမ္းအင္ဆံုးရွဳံးမွဳစုစုေပါင္း (Total losses ) ၏ ၁၄%ၿဖစ္သည္။

 

friction losses သည္ေမာ္တာတြင္တပ္ဆင္ထားေသာ ဘယ္ရင္(Bearing) မွ ၿဖစ္ေပၚလာသည္။

 

Stray losses

Load current က induce လုပ္ေသာေၾကာင့္ leakage fluxes မ်ားၿဖစ္ေပၚလာကာ စြမ္းအင္ဆံုးရွဳံးမွဳၿဖစ္ေပၚၿခင္းၿဖစ္သည္။ Surface losses ႏွင့္  Harmonics တုိ့သည္ Stray losses ထဲတြင္ပါဝင္သည္။ Stray losses ကို အတိအက်သိနုိင္ရန္အလြန္ခက္ခဲသည္။ အၿခားေသာ မေၿပာပေလာက္သည့္ losses မ်ားသည္ Stray losses တြင္ အက်ံဳးဝင္သည္။

 

Stator losses, Rotor losses ႏွင့္ Stray losses တို့သည္ ကို “on load losses” ဟုေခၚသည္။ “on load losses” သည္ ေမာ္တာ ၏ loading % ေပၚတြင္မူတည္သည္။ loading % မ်ားေလ “on load losses” မ်ားေလၿဖစ္သည္။

 Stray losses သည္ စြမ္းအင္ဆံုးရွဳံးမွဳစုစုေပါင္း (Total losses ) ၏ ၁၅%ၿဖစ္သည္။

 

 

Copper loss (58%)

Stator Loss

Rotor Loss

Core (Iron) loss

(12%)

Eddy Current loss

Hysteresis loss

Windage and Friction loss

(14%)

External Fan Windage

Internal Fan Windage

Bearing , Grease

Stray loss (15%)

Surface loss

Harmonics

Leakage flux

 

 

 

 

ေကာင္းထက္ညြန့္

MOTOR EFFICIENCIES

 

High-efficiency motors are built to reduce motor energy loss.

  • Larger-diameter wire, increasing the volume of copper by 34 to 40%. This change reduces copper losses that result naturally from current passing through the copper-wire windings.
  • Larger wire slots to accommodate larger wire. This reduces the amount of active steel in each steel lamination.
  • Longer rotor and stator core to compensate for the loss of steel and the resultant need to add more laminations.
  • High-grade silicon steel laminations approximately 0.018 in. thick, having an electrical loss of 1.5 W/lb. The chemical makeup and thinner gage of the laminations, plus a coating of inorganic insulation on each piece, reduce eddy current losses. Special annealing and plating of rotor and stator components and use of high-purity cast aluminum rotor bars reduce hysteresis losses.
  • Higher-grade bearings reduces friction loss.
  • Smaller, more efficient designs reduce windage losses in fan-cooled motors.
  • Tighter tolerances and more stringent manufacturing-process control reduce losses from unplanned conducting paths and stray load phenomena.

 http://dcacmotors.blogspot.com/2009/04/losses-and-efficiency-of-induction.html

 

Motor Losses ႏွင့္သက္ဆုိင္ေသာ ACMV Lecture မ်ား (1 Lectures)
1 AC Induction Motor Motor Losses-လွ်ပ္စစ္ေမာ္တာ၏ စြမ္းအင္ဆံုးရွဳံးမွ Read
   

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