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

■ C. Electric Equipment

The specific operating conditions of deck machinery cargo handling equipment & some other types of ship’s gear, i.e. a high frequency of startings & heavy starting & breaking conditions necessitated development of special AC motors with a number of specific features for use in these electric drives. The series of such motors covers power ratings from 1 to 100 kw & consists of nine frame sizes. The motors come in different design versions. Commonly used is the version with a ribbed cast frame externally cooled by a shaft-mounted fan.

The motors are intended for installation on weather decks, in places where they are not exposed to direct splashes of sea waves.

The frame, end shields, shafts & other structural components • have robust construction & are capable of withstanding large overloads during starling & when affected by external shock impacts.. The construction of bearing assemblies & shafts ensures long service life with a large number of on-load startings & with loads varying both in magnitude & sign.

In principal design versions the short-circuited rotors of the motors have a cage cast from a high-resistance non-corrosive aluminium alloy. In some design Versions the cage is made up of copper bars welded at the ends to short-circuiting brass rjngs.

To ensure high strength & relfability the short-circuited windings are manufactured with special thoroughness.

The motor have terminal boxes with leads brought out through glands. In terminal boxes connections are effected to terminal racks.

As the motors are intended for installation on deck where abrupt temperature variations are possible, special holes агё provided in the motors for the discharge of condensate forming on their inner surfaces. ?.(

Flange-type motors must not be directly coupled wifti machine spaces where the oil level is above the lower bearing cap. This is due to the fact that, as the shaft seals wear off, oil is bound to leak inside the motor & such leaks cannot be checked.

D. Emergency source of electric power is a source of electric power intended to supply essential consumers on board ship in case the voltage disappears from the main switchboard.

Emergency lighting is lighting of ship’s compartments & spaces by means of lighting fixtures fed from the emergency source of power or from the temporary emergency source of power.

Safety voltage is any voltage not dangerous to the personnel (if the windings of transformers, converters & other devices to step down voltage are isolated electrically).

Essential equipment is equipment ensuring, under normal operation, safe navigation, safety of human life on board ship, safety of cargo.

E. For safeguarding the spare motors it is recommended to keep them in the Manufacturer’s packing.

Keep the spare parts under the same conditions as the motor.

Open the cases containing the spare parts only in the case of long-term storage exceeding 12 months or in emergencies.

When shifting about the packed motor, observe strictly the inscriptions “Top” & “Don’t roll over”.

Make sure the premises for storage are dry, clean & amply ventilated. Daily temperature fluctuations within the premises shouldn’t exceed 10°C & the relative humidity of a'ir 75%. The premises must be free of vapours detrimental to insulation & non-painted metal parts.

F. In case of faults, check that all terminals are securely fastened & that there are no loose connections.

If alternator voltage fails to rise during voltage built-up, check that:

a) excitation switch is closed;

b) fuses are intact & tightened;

c) thermal relays have not tripped;

d) the residual voltage is sufficient.

In case of low residual voltage, the excitation can be initiated by connecting a separate DC source to terminals located at the regulator terminal board.

e) the diodes are in order.

A defective diode conducts in both directions or in neither direction. Disconnect the diodes & test by means of an ohmmeler or a flash light battery & a lamp.

The faulty diode causes increased exciter current demand which may be detected using an ammeter.

Warning: No “Megger” or high voltages test to be carried out until all diodes & thyristors are"shortened or disconnected.

G. Arrangement of Machinery & Equipment

They are to be so arranged as to provide free access to them for attendance & overhaul. ч

. If auxiliary boilers are installed in one common space with the internal combustion engines precautions must be taken to protect against the effect of flame from the furnace.

Fuel tanks, as a rule, not to be installed above the ladders, main engines, steam boilers, electric equipment & the main engine control station.

The machinery driving the cargo pumps & ventilators in pump rooms of tankers are not to be installed in cargo pump rooms, but spaces adjacent to the pump room.

Drive shafts are to be fitted with glands efficiently lubricated from outside the pump room. Those parts of the glands, which due to the bad centricily of the drive shaft or damage of the bearings might contact, shall be made of material that will not initiate sparks.

H. Insulation Resistance

The rules of maintenance for ship’s electrical' equipment prescribe minimum value of insulation resistance equal to 200 kom for alternators, motors & power feeders.

The measurement of insulation resistance.should be made after taking into account the temperature. This is because the insulation resistance increases as the temperature falls. The insulation test should be for one minute.

It is important that the insulating resistance during the test is constant.

I. Connection

> Three-phase commutator motors have their primary winding located in the rotor & for that reason the line should be connected to the slip-rings terminals.

For starting there is, generally, no other apparatus required than a circuit-breaker which should be mounted within easy access & close to the machine.

On machines which have no indication of the direction of rotation the direction can be reversed simply by interchanging two of the phases where the slip-rings are connected to the line. On machines where an arrow indicates the direction of rotaton the direction can only be reversed by following the special instructions supplied with the machine. If.it is doubtful whether an alteration has been carried out correctly or whether an alteration has been carried out without reversing the indicating arrow of the machine should be checked before being put into service by a no-load test run.

/. All Motors are Delivered Ready for Operation.

Before starting the motor for the first time after mounting or after a long idle period, attend to the following:

- clean the motor of dust & blow it through with clean compressed air under a pressure not exceeding 2 kgf/сщ 2;

- verify tightness of foundation bolts; ’*

- check starting & protective equipment in accordance with

respective instructions; £ ,:

- check grounding of the motor & cable sheathing;"

- check insulance of the stator winding.

To make sure the motor is assembled correctly, start it up by switching on the full voltage of the mains. Let it run for two hours. During this time watch the temperature of bearings & see that there is no vibration, abnormal nojse, etc.

In case of abnormal operation, stop the motor, inspect it & eliminate detected flaws. Stop the motor by disconnecting it from the mains.

K. It is important that these instructions are at hand at the place of mounting, & the complete instruction should be carefully read before mounting.

The alternator is delivered assembled. Single bearing machines have a supporting device at driving end. The supporting device is also a locking system of the rotor during transport.