Кущ Т.Ю., Воловник М.С. Основы английского языка для судовых электриков (1998)

Alignment of the alternator is to be done against the driving machine only.

1. Alternator feet & flange as well as the bedplate must be cleaned & free of metal swarf,tectyl etc.

2. Place the alternator on the bed, a few mm from the driving machine.Adjust the centerline of the two machines by using a dial indicator & turn the driving machine. Control the parallel position of the two flanges.

3. Move the alternator to the driving machine & fix the two flanges by means of preliminary bolts.

4. Locking ring & support ring to be removed. Clean the bearing & shaft. The set may now be turned.

1. When the alternator is aligned as described, the rotor must be in the correct position in the stator.

2. Bolls in shaft flange & stator feet to be fitted, & finally the dowel pins. ,

L. If voltage drops when the relay opens, check that:

a) there are no defective fuses or any breaks in the connections between the busbars & the terminals;

b) there is voltage at the regulator terminals;

c) there is voltage at transformer;

d) the regulator elements work as described.

If voltage is higher than desired & cannot be reduced, check

that:

a) the connections from busbars to regulator terminals are

tight;

b) regulator, specially the measuring circuit, works.

If voltage decreases considerably when load is applied, probably, one or more of the rectifiers are faulty.

Check that there are no faulty diodes in the rotating rectifier bridge. This could be done by checking the alternator excitation current. Abnormally high excitation current indicates one or more faulty diodes.

Af. General Pointers on Maintenance & Supervision

■ In the course of operation realize the general watch & service in accordance with the instructions.

When mounting the motor at the installation side, set reliable protective devices ensuring the safety of attendance. Keep them in good condition & observe the rules of safety engineering.

Keep all bolted & screwed connections as well as the parts coupling the motor to the mechanism well tight & secure from selfloosening. Make sure the motor is well aligned with the mechanism.

If all these requirements are observed, the motors ensure up to 2,000 hours of uninterrupted operation without direct attendance of the stator winding, operation of bearings & securing of the motor.

N. In case tne bearings are in good state, this is testified by an even drone & absence of knocks & jolts. To run the bearings use grease specified in certificate.

Change grease in the bearings not less than once in 4,000 hours, or once in three years.

Do not allow the bearings to warm up above +60°C at an ambient temperature of +40°C.

Machines should be kept clean & free from dust, dirt & oil & should, therefore, be cleaned occasionally with compressed air or a brush, or by wiping them down with pieces of cloth.

Take care to see that the insulation of brush holders, slip-rings, terminals etc. is well cleaned to remove the carbon dust which easily collects when the machine is running.

The winding should be cleaned in the same manner. If the dirt or dust has become clotted with grease or oil the winding should be wiped off with rags damped with petrol or a similar solvent. Be careful not to use a solvent which also dissolves the varnish & impregnation of the windings. When using petrol great care must be exercised on account of the fire hazard, taking account of nearby apparatus where sparking might occur.

P. If after having synchronized the alternators, the reactive load (the excitation current) increases in one alternator & decreases towards zero in the other it means that the first mentioned alternator is over-excited & the other is under-excited. Then check that: a) fuses are intact; b) there is no break or loose connections in the system giving overexcitation; c) current transformer is connected to phase & that it is connected to the regulator with correct polarity; d) settings of resistance are correctly adjusted.

If there are power oscillations in parallel operation, check whether the alternator speed is constant at no-load, whether the oscillations disappear or are considerably damped when the system speed governer is kept at a constant level. If this is the case, the damping of the speed regulator should be increased.

Also check if the frequency-load-characteristic decreases when a certain alternator is connected. This is done by connecting alternately two & two alternators in parallel. fc

Checking the voltage regulator. The regulator consists of a few parts which may be checked using the following procedure...

Caution. Great care should be exercised when checking & replacing parts. Most parts in the regulator are sensitive to excessive voltage, heat & mechanical forces.

Excitation. The system is initiated as follows: the alternator is brought to nominal speed, the excitation switch is closed.

At 30-40% of nominal alternator voltage will open & the regulator will bring the voltage up to nominal value.

As the regulator has voltage built-up, no operation of switches is needed.If the excitation switch has been employed for deexcitalion, it must be closed to get voltage built-up.

Deexcitation. Alternator speed shut down with excitation switch closed results in deexcitation as the speed decreases. If deexcitation is done by turning excitation switch off, the alternator circuit breaker should be in the off-position to avoid system disturbances.

In some systems switch may be opened by means of the tripping coil controlled by external protection devices.

R. At the modern stage of scientific & technological development, microelectronics is rapjdly gaining ground & its advances today largely determine progress in many branches of industry. The ne,ed for lighter, more compact, & more reliable equipment capable of performing the functions of growing complexity has led to research into ways & means of achieving the aims. Search for new approaches to low-cost, & reliable systems has brought the concept of producing circuits in one tiny die.

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Вариант 1 - об инструкции по эксплуатации асинхронного двигателя;

Вариант!! - о неполадках в работе двигателя переменного

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а.с., ас, AC alternating current -