Reasons for Generator Set Overheat And Abnormal Noise

The operating temperature of diesel generator has a clear allowable range. If it exceeds or falls below the allowable temperature range, the diesel generator may be damaged and even cause accidents. There are many reasons for the overheating of diesel generators.

1. The diesel generator does not operate in accordance with the prescribed technical conditions, such as too high stator voltage, increased iron loss, too large load current, increased copper loss in stator winding, too low frequency, which will slow down the speed of cooling fan and affect the heat dissipation of generator, and the power factor is too low. It will increase the rotor excitation current and then cause the rotor to heat. Users should check that the monitoring instrument's instructions are correct. If the monitor is abnormal, must carry on the necessary adjustment and the processing, causes the generator to operate according to the stipulated technical condition.

2. The three-phase load current of the diesel generator is unbalanced, and the over-loaded one-phase winding will overheat. If the difference of the three-phase current exceeds the rated current by 10 percent, it is a serious phase current imbalance, and the three-phase current imbalance will produce a negative sequence magnetic field, thus increasing the loss. Causes the magnetic pole winding and hoop and other parts to heat. The three-phase load should be adjusted to keep the current balance as far as possible.

3. The air duct is blocked by dust and the air is not well ventilated, which makes it difficult for the diesel generator to dissipate heat.

4. If the inlet air temperature is too high or the inlet water temperature is too high, the cooler will be blocked. The inlet or inlet temperature should be lowered to remove the clogging in the cooler. Before the fault is eliminated, the generator load should be limited to reduce the generator temperature.

5. Bearings with too much or too little grease should be added as prescribed, usually 1 / 2 / 1 / 3 of the bearing chamber (upper limit of low speed and lower limit of high speed), and should not exceed 70% of the bearing room.

6. Bearing wear. If the wear is not serious, the bearing will overheat locally, and if the wear is serious, the stator and rotor may be friction, which will cause the stator and rotor to overheat. Bearings should be checked for noise, if any stator and rotor friction, should immediately stop for repair or replacement of bearings.

The noise of diesel generator mainly comes from diesel engine and generator. In order to reduce the noise of generator set, the main noise source should be controlled, and the key to the control is to find the main sound source accurately.

I Main noise sources of Diesel engines

1. Intake and exhaust noise

Intake and exhaust noise is the strongest noise source of diesel engine.

The intake noise is mainly the pressure pulsation of air in the intake pipe, the low frequency noise, the high frequency eddy current noise produced by the air flowing through the inlet valve section at high speed, and the noise of the turbocharger compressor of the turbocharged diesel engine.

The exhaust noise is mainly the pressure pulsation of exhaust gas in the exhaust pipe, which produces low and medium frequency noise, and the high frequency eddy current noise at the flow section of the exhaust valve.

2. burner noise

The combustion of combustible mixture in cylinder causes the rapid change of gas pressure, which causes the piston, cylinder head, connecting rod, piston pin, crankshaft and other parts to be subjected to impact load, resulting in structural vibration and noise.

3. mechanical noise

Due to the periodic changes and impact of the forces between the parts of the diesel engine, the surface vibration produces noise. The mechanical noise increases rapidly with the speed of the engine. The main parts of the mechanical noise are piston, cylinder head, cylinder block, cylinder liner, connecting rod, piston pin, crankshaft, valve train, gear, spray. The design of the components, the quality of the manufacturing and the selection of materials have an important effect on the noise. The structural stiffness of the diesel engine, the speed of the engine and the clearance of the moving parts are the main factors affecting the mechanical noise.

II Main noise sources of generators

1. ventilation noise

Electromagnetic noise is caused by the interaction of stator and rotor magnetic field in the air gap of generator to produce radial force varying with time and space, which causes the stator core and seat to deform periodically and cause vibration and noise.

2. electromagnetic noise

Electromagnetic noise is caused by the interaction of stator and rotor magnetic field in the air gap of generator to produce radial force varying with time and space, which causes the stator core and seat to deform periodically and cause vibration and noise.

3. mechanical noise

The mechanical noise of generator includes mechanical vibration and noise caused by centrifugal force caused by rotor mechanical imbalance, vibration noise of bearing, sliding contact noise of brush collector ring or commutator, axial vibration noise of end cover excited by bearing vibration.