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Generator Cooling System

DUNIAPEMBANGKITLISTRIK.COM - The heat in the generator or alternator cooling system is caused by copper loss and iron loss. What is meant by copper loss is heat caused by the loading current that flows through the conductor of copper stator and rotor whose power can be calculated I2R.

While iron losses are losses caused by heat generated by the eddy current that occurs in the stator core or rotor. In addition to the heat caused as mentioned above, heat also occurs due to friction and wind (windange).

Excessive heat resulting from as described above on the generator needs to be prevented, this can result in damage to the conductor insulation or burning, therefore the need for cooling the generator. Losses that cause heat must be cultivated small so that no more than 2% of the alternator output.


Generator Cooling Media

To absorb and dissipate heat (dissipation) arising in the alternator that is operating can use some cooling media. The types of generator cooling media commonly used include: Air, Hydrogen Gas, Water.

Naturally, the greater the alternator capacity, the greater the heat generated. The most effective generator cooling media is water, but water has many obstacles that must be dealt with, besides the expensive installation, the maintenance is difficult.

Cooling of the generator with air is limited to alternators of small capacity or for exciter engines. Then for alternators that are large enough in capacity, the simplest of handling but that does not mean the easiest, and effective in absorbing heat compared to air is hydrogen gas.


Cooling Generator with Hydrogen Gas

Cooling the generator with hydrogen gas is the most effective compared to air. But Hydrogen is very susceptible to explosion hazards when mixed with air under conditions of 4% to 75%, so care must be taken. The advantages of hydrogen gas compared to air can be seen in the following characteristics:


Heat Specifications
Density
Thermal Conductivity
Heat Transfer Coefficient
ATM Hydrogen Pressure
1.0
1.0
1.0
1.0
0.34 b
14.35
0.07
6.69
1.55
1.0 b
14.35
0.14
6.69
1.65
2.0 b
14.35
0.22
6.69
2.65
3.0 b
14.35
0.30
6.69
4.4
4.0 b
14.35
0.30
6.69
4.85

As in the table above it is stated that the density of ordinary air compared to hydrogen is 1: 0.14, heat conductivity is 1: 7, then hydrogen gas can be used to cool the alternator with good enough effectiveness. From these advantages can be concluded as follows:

- Low density so that the friction loss, noise is reduced and the power of the fan to circulate is also low
- High heat transfer coefficient compared to air so that it can absorb more heat.
- High heat conductivity compared to air, so it can conduct more heat.
- Not corrosive.
- Low risk of fire, pure hydrogen does not help fire.
- Low maintenance costs, this is because the gas cycle is closed so that the noise is maintained.

To keep the temperature of the cooling media does not increase continuously, then after absorbing heat, the cooling media must be cooled to remove the heat in the womb. Therefore the cooling media must be cooled and circulated.

As a cooling medium for generators, hydrogen usually uses water through a box cooler or water pipes placed inside the stator frame. As for passing hydrogen gas into the cooler box and the cracks of the stator and rotor coils, it is necessary to have circulation with sufficient pressure.

To circulate hydrogen using a blower or rotor, it is necessary to circulate with enough pressure. To circulate hydrogen using a blower or rotor blade mounted on the alternator shaft.

The conventional hydrogen circulation system inside the alternator (conventional hydrogen cooled) using two blower units, each of which is mounted at the ends as shown in the following figure :

Conventional Hydrogen Generator Coolant Circulation System

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