One hall is located a mill for grinding limestone.
Case 1
Drive motor has an output of 4,000 kw and is mounted in ventilated and died in a separate room. For air cooling the room where the engine should be determined amount of waste heat from the engine windings. The air circulated in the room over the area where the engine takes a quantity of heat equal to that generated by the coils. The amount of heat generated in ventilated electric motor corresponding losses.
Q = F x K x P ( 1-ŋ me ) kcal/h
ŋ me : randamentul motorului electric
| Electric motor efficiency ŋ me | Rated motor power P( kw ) |
| 0.5÷0.6 | < 0.25 |
| 0.8 | 0.25 ÷ 1 |
| 0.85 | 1 ÷ 10 |
| 0.9 | > 10 |
F : conversion factor of electricity into heat
F = 860 kcal/kwh
P : Rated motor power written on the plate.
K : a coefficient that takes account of real power absorbed from the mains supply relative to nominal power.
This coefficient is a product:
K = K1 x K2 x K3 where
K1 : Use of rated power factor
K2 : load factor of engine
K3 : simultaneetate factor.
| Factor | |
| use of nominal power | K1 = 0.7 ÷ 0.9 |
| engine load | K2 = 0.5 ÷ 0.8 |
| simultaneetate factor. | K3 = 0.5 ÷ 1 |
was chosen
| Factor | |
| use of nominal power | K1 = 0.8 |
| engine load | K2 = 0.7 |
| simultaneetate factor. | K3 = 1 |
ŋ me = 0.9
Q = 860 x 0.8 x 0.7 x 1 ( 1-0.9 )
Q = 192.640 kcal/h = 224000 w
Case 2
Drive motor has an output of 4,000 kw and is mounted in the same room with the mill for grinding limestone ventilated. The entire quantity of electricity absorbed from the network is transformed into heat which remains in the ventilated space.
Q = F x K x P ( kcal/h )
F : conversion factor of electricity into heat
F = 860 kcal/kwh
P : Rated motor power written on the plate.
K : a coefficient that takes account of real power absorbed from the mains supply relative to nominal power.
This coefficient is a product:
K = K1 x K2 x K3 where
K1 : Use of rated power factor
K2 : load factor of engine
K3 : simultaneetate factor.
| Factor | |
| use of nominal power | K1 = 0.7 ÷ 0.9 |
| engine load | K2 = 0.5 ÷ 0.8 |
| simultaneetate factor. | K3 = 0.5 ÷ 1 |
was chosen
| Factor | |
| use of nominal power | K1 = 0.8 |
| engine load | K2 = 0.7 |
| simultaneetate factor. | K3 = 1 |
Q = 0.8 x 0.7 x 0.8 x 860 x 4000
Q = 1.541.120 kcal/h = 1792000 w
Case 3
Drive motor has an output of 4,000 kw and is mounted in a separate room and the mill is in the room ventilated. The amount of heat generated in ventilated corresponding transmitted power grinding mill scale.
Q = F x K x P x ŋ me ( kcal/h )
ŋ me : electric motor efficiency
| Electric motor efficiency ŋ me | Rated motor power P( kw ) |
| 0.5÷0.6 | < 0.25 |
| 0.8 | 0.25 ÷ 1 |
| 0.85 | 1 ÷ 10 |
| 0.9 | > 10 |
F : conversion factor of electricity into heat
F = 860 kcal/kwh
P : Rated motor power written on the plate.
K : a coefficient that takes account of real power absorbed from the mains supply relative to nominal power.
This coefficient is a product:
K = K1 x K2 x K3 unde
K1 : Use of rated power factor
K2 : load factor of engine
K3 : simultaneetate factor.
| Factor | |
| use of nominal power | K1 = 0.7 ÷ 0.9 |
| engine load | K2 = 0.5 ÷ 0.8 |
| simultaneetate factor. | K3 = 0.5 ÷ 1 |
was chosen
| Factor | |
| use of nominal power | K1 = 0.8 |
| engine load | K2 = 0.7 |
| simultaneetate factor. | K3 = 0.8 |
Q = 0.8 x 0.7 x 0.8 x 860 x 4000 x 0.9
Q = 1.387.008 kcal/h = 1.733.760 w
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