Daewoo DAGFS Series, User Manual

Page: 87 / 91

Blown Air Drying
Remove the covers from all apertures to allow the escape of the water-laden air. During drying,
air must be able to flow freely through the generator in order to carry off the moisture.
Direct hot air from two electrical fan heaters of around 1-3 KW into the generator air inlet aper-
tures. Ensure the heat source is at least 300mm away from the windings to avoid over heating
and damage to the insulation.
Apply the heat and plot the insulation value at half hourly intervals. The process is complete
when the parameters covered in the section entitled, 'Typical Drying Out Curve', are met.
Remove the heaters, replace all covers and re-commission as appropriate.
If the set is not to be run immediately ensure that the anticondensation heaters are energized,
and retest prior to running.
Shirt Circuit Method
NOTE: This process shou ld only be performed by a competent engineer familiar with safe
operating practices within and around generator sets of the type in question. Ensure the gene-
rator is safe to work on, initiate all mechanical and electrical safety procedures pertaining to the
genset and the site.
Bolt a short ci rcuit of adequate current carrying capacity, across the main terminals of the
generator. The shorting link should be capable of taking full load current.
Disconnect the cables from terminals "X" and "XX" of the AVR.
Connect a variable de supply to the "X" (positive) and "XX" (negative) field cables. The de
supply must be able to provide a current up to 2.0 Amp at 0-24Volts.
Position a suitable ac ammeter to measure the shorting link current.
Set the de supply voltage to zero and start the generating set. Slowly increase the de voltage to
pass current through the exciter field winding. As the excitation current increases, so the stator
current in the shorting link will increase. This stator output current level must be monitored, and
not allowed to exceed 80% of the generators rated output current.
After every 30 minutes of this exercise: Stop the generator and switch off the separate excita-
tion supply, and measure and record the stator winding IR values, and plot the results.
The resulting graph should be compared with the classic shaped graph. This drying out proce-
dure is complete when the parameters covered in the section entitled 'Typical Drying Out
Curve' are met.
Once the insulation Resistance is raised to an acceptable level minimum value 10MΩ - the de
supply may be removed and the exciter field leads "X" and "XX" re-connected to their terminals
on the AVR.
Rebuild the genset, replace all covers and re-commission as appropriate.
If the set is not to be run immediately ensure that the anticondensation heaters are energised,
and retest the generator prior to running.
Typical Drying Out Curve
Whichever method is used to dry out the generator the resistance should be measured every
half-hour and a curve plotted as shown.(Fig 9)
The illustration shows a typical curve for a machine that has absorbed a considerable amount
of moisture. The curve indicates a temporary increase in resistance, a fall and then a gradual
rise to a steady state. Point 'A', the steady state, must be greater than 1.0MΩ (If the windings
are only slightly damp the dotted portion of the curve may not appear).
For general guidance expect that the typical time to reach point 'A' will be approximately 3
hours for a LV 6 generator.
Drying should be continued after point "A" has been reached for at least one hour.
It should be noted that as winding temperature increases, values of insulation resistance may
significantly reduce. Therefore, the reference values for insulation resistance can only be esta-
blished with windings at a temperature of approximately 20°C.
After drying out, the insulation resistances should be rechecked to verify minimum resistances
quoted above are achieved. On re-testing it is recommended that the main stator insulation
resistance is checked as fol lows:
-Separate the neutral leads.
Ground V and W phase and megger U phase to ground
Ground U and W phase and megger V phase to ground
Ground U and V phase and megger W phase to ground.
If the minimum value of 1.0MΩ is not obtained, drying out must be continued and the test
repeated.
If the minimum value of 1.0MΩ for all components cannot be achieved rewinding or refurbish-
ment of the generator will be necessary.
The generator must not be put into service until the minimum value, Of 1.0MΩ for all compo-
nents, can be achieved.
8.2 BEARINGS
All bearings are supplied from the factory pre-packed with Kluber Asonic GHY 72 grease.
Do not mix kluber Asonic GHY 72 with any grease of different specifications. Mixing grease of
differing specifications will reduce bearing life. The specification for Kluber Asonic FHY 72 is
available on request from the factory.
Sealed for life bearings are fitted with integral seals and are not re-greasable.
BEARING LIFE
IMPORTANT! The life of a bearing in service is subject to the working conditions and the
environment.
IMPORTANT!
High levels of vibration from the engine or misalignment of the set will
stress the bearing and reduce its service life. If the vibration limits set out
im BS 5000-3 and ISO 8528-9 are exceeded bearing life will be reduced.
Refer to 'vibration’ below.
IMPORTANT! Long stationary periods in an environment where the generator is subject
to vibration can cause false brinneling, which puts flats on the ball and
grooves on the races, leading to premature failure.
IMPORTANT! Very humid atmospheric or wet conditions can emulsify the grease causing
corrosion and deterioration of the grease, leading to premature failure of
the bearings.
HEALTH MONLTORING OF THE BEARINGS
It recommends that the user check the bearing condition, using monitoring equipment, to
determine the state of the bearings. The 'best practice' is to take initial readings as a base line
and periodically monitor the bearings to detect a deteriorating trend. It will then be possible to
plan a bearing change at an appropriate generating set or engine service interval.
VLBRATION
The generators are designed ti withstand the vibration levels encountered on generating sets
built to meet the requirements of ISO 8528-9 and BS5000-3. (Where ISO 8528 is taken to be
broad band measurements and BS5000 refers to the predominant frequency of any vibrations
on the generating set.)
Definition of BSS000-3
Generators shall be capable of continuously withstanding linear vibration levels with amplitudes
of 0.25 mm between 5 Hz and velocities of 9.0 mm/s. Between 8 Hz and 200 Hz when measu-
red at any point directly on the carcass or main frame of the machine. These limits refer Only to
the predominant frequency of v ibration of any complex waveform.
Definition of ISO 8528-9
ISO 8528-9 refers to a broad band of frequencies, the broad band is taken to be between 2
Hertz and 300 Hertz. The table below is an example from ISO 8528-9 (value 1 ). This simplified
table lists the vibration limits by kVA range and speed for acceptable genset operation.
IMPORTANT! Exceeding either o f the above specifications will have a detrimental effect
on the life of the bearing. This will invalidate the generator warranty. If you
are in any doubt, contact Newage International limited.
If the vibration levels of the generating set are not within the parameters quoted above.
1. consult the genset builder. The genset builder should address the genset design to reduce
the vibration levels as much ad possible.
2. Discuss the impact of not meeting the above levels on both bearing and generator life
expectancy.
Where requested, or deemed necessary, Newage will work with the genset builder in an
attempt to find a satisfactory solution.
BEARING 'SERVICELIFE' EXPECTANCY
Bearing manufacturers recognize that the "service life" of their bearings is dependent upon
many factors that are not in their control, they cannot therefore quote a "service life".
Although "service life" cannot be guaranteed, it can be maximized by attention to the genera-
ting set design. An understanding of the genset application will also help the user to maximize
the service life expectancy of the bearings. Particular attention should be paid to the alignment,
reduction of vibration levels, environmental protection, maintenance and monitoring procedu-
res. We does not quote life expectancy figures for bearings, but suggests practicable replace-
ment intervals based on the L 10 life of the bearing, the grease and the recommendations of
the bearing and grease manufacturers. For general-purpose applications, provid ing the vibra-
tion levels do not exceed the levels stated in ISO8528-9* and BS5000-3* and the ambient
temperature does not exceed 50°C the following approximations can be applied when *
(See section on vibration)
Sealed for life Bearings. - Approximately 30,000hours.
Re-greaseable bearings.- Approximately 40,000hours.
This is provided the correct maintenance is carried out, and only Kluber Asonic GHY 72 grease
(or equivalent) is used in all bearings. It is important to note that bearings in service. Under
good operating conditions, can continue to run beyond the remembered re placement period.
It should also be remembered that the r isk of bearing failure increases with time.
8.3 ALR FILTERS
Air filters for the removal of airborne particulate matter (dus) are offered as an addition to the
standard build option. Filters on it's need to be ordered with the generator. Air filters need to
be charged with oil before the genset is put to work (see 8.3.2) The frequency of fi lter mainte-
nance will depend upon the severity of the site conditions. Regular inspection of the elements
will be required to establish when cleaning is necessary.
Danger! Removal of filter elements enables access to LIVE parts. Only remove elements
with the generator out of service.
8.3.1 CLEANING PROCEDURE
Remove the filter elements from the filter frames. Immerse of flush the element with a suitable
degreasing agent until the element is cleas.
As an alternative procedure a high-pressure water hose with a flat nozzle can be used. Sweep
the water spray back and forth across the element from the clean side (fine mesh side of
element) holding the nozzle firm ly against the element surface. Cold water may be adequate
depending upon type of contamination although hot water is preferable.
The element can be inspected for cleanliness by looking through the filter towards the light.
When the roughly clean, no cloudy areas will be seen. Dry elements thoroughly before attemp-
ting to carry out the recharging procedure.
8.3.2 RECHARGING (GHARGING) AIR FILTERS
Charging is best done by totally immersing the dry element into a dip tank containing "Filterko-
te Type k" or commercial lubricating oil SAE 20/50. oils of higher or lower viscosity are not
recommended.
Allow elements to completely drain before refitting the elements into the frames and putting
into service.
8.4 FAULT FINDING
IMPORTANT! Before commencing any faultfinding procedures, examine all wiring for
broken or loose connections.
Two types of AVR can be fitted to the WH generator. The Refer to the generator nameplate for
type of AVR fitted.
8.4.1 MX341 AVR, FAULT FINDING
8.5 SEPARATE EXCITATION TEST PROCEDURE
The generator windings, diode assembly and AVR can be checked using the appropriate
following sections.
8.5.1 GENERATOR WINDINGS, ROTATING DIODES and PERMANENT MAGNET GENERA-
TOR (PMG)
IMPORTANT! The resistances quoted apply to a standard winding. For generators
having windings or voltages other than those specified refer to fac-
tory for details. Ensure all disconnected leads are isolated and free
from earth.
IMPORTANT! Incorrect speed setting will give proportional error in voltage out put.
Checking Generator Windings and Rotating Diodes
This procedure is carried out w ith lead X and XX disconnected at the AVR or transformer
control rectifier bridge and using a 12 volt d. c. Supply to leads X and XX.
Start the set and run at rated speed.
Measure the voltages at the main output terminals U, V and W. if voltages are balanced and
/-10% of the generator nomial voltage, refer to 7 .5.1.1.
Check voltages at AVR terminals 6, 7 and 8. These should be balanced and between 170-250
volts.
If voltages at main terminals are balanced but voltage at 6, 7
and 8 are unbalanced, check continuity of leads 6,7 and 8.
If voltages are unbalanced , refer to 7 .5.1.2.
8.5.1.1 BALANCED MAIN TERMINAL VOLTAGES
If all voltages are balanced within 1 % at the main terminals, it can be assumed that all exciter
windings, main windings and main rotating diodes are in good order ,and the fault is in the
AVR or transformer control. Refer to subsection 7 .3.2 for test procedure.
If voltages are balanced but low, there is a fault in the main excitation windings or rotating
diode assembly. proceed as follows to identity:-
Rectifier Diodes
The diodes on the main rectifier assembly can be checked with a multimeter. The flexible leads
connected to each diode should be disconnected at the terminal end, and the forward and
reverse resistance checked. A healthy diode will indicate a very high resistance ( infinity) in the
reverse direction, and a low resistance in the forward direction. A faulty diode will give a full
deflection reading in both directions with the test meter on the 10,000 ohms scale, or an
infinity reading in both directions. On an electronic digital meter a healthy diode will give a low
reading in one direction, and a high reading in the other.
Replacement of Faulty Diodes
The rectifier assembly is split into two plates, the positive and negative, and the main rotor is
connected across these plates. Each plate carries 3 diodes, the negative plate carrying negati-
ve biased diodes and the positive plate carrying positive biased diodes. Care must be taken to
ensure that the correct polarity diodes are fitted to each respective plate. When fitting the
diodes to the plates they must be tight enough to ensure a good mechanical and electrical
contact, but should not be over-tightened. The recommended torque tightening is 4.06-4.74
Nm (36-42Ib in).
Surge suppressor
The surge suppressor is a metal-oxide varistor connected across the two rectifier plates to
prevent high transient reverse voltages in the fie ld winding from damaging the diodes. This
device is not polarized and will show a virtually infinite reading in both directions with an ordi-
nary resistance meter. If defective this will be visible by inspection, since it will normally fail to
short circuit and show signs of disintegration. Replace if faulty.
If after establishing and correcting any fault on the rectifier assembly the output is still low
when separately excited, then the main rotor, exciter stator and exciter rotor winding resistan-
ces should be checked (see Resistance charts ), as the fault must be in one of these windings.
The exciter stator resistance is measured across leads X and XX. The exciter rotor is conne.
Main Excitation Windingscted to six studs that also carry the diode lead t erminals. The main
rotor winding is connected across the two rectifier plates. The respective leads must be
disconnected before taking the readings.
8.5.1.2 UNBALANCED MAIN TERMINAL VOLTAGES
If voltages are unbalanced, this indicates a fault on the main stator winding or main cables to
the circuit breaker. NOTE: Faults on the stator winding or cables may also cause noticeable
load increase on t he engine when excitation is applied. Disconnect the main cables and sepa-
rate the winding leads U1-U2,(U5-U6),V1-V2,(V5-V6),W1-W2,(W5-W6) to isolate each winding
section. Note: -leads suffixed 5 and 6 apply to 12 wire windings only.
Measure each section resistance values should be balanced and /- 10% fo the value.
Measure insulation resistance between sections and each section to earth.
Unbalanced or incorrect winding resistances and/or low insulation resistances to earth indica-
te rewinding of the stator will be necessary. Refer to removal and replacement of component
assemblies' subsection 8.5.3.
8.5.2 AVR FUNCTION TEST
All types of AVR's can be tested with this procedure:
1. Remove exciter field leads X & XX (F1 &F2) from the AVR terminals X & XX (F1 &F2).
2. Connect a 60W 240V household lamp to AVR terminals X & xx (f1 &f2).
3. Set the AVR VOL TS control potentiometer fully clockwise.
4. Connect a 12V, 1.0A DC supply to the exciter field leads X & XX (F1 &F2) with X (F1 )to the
positive.
5. Start the generating set and run at rated speed.
6. Check that the generator output voltage is /- 10% of rated voltage.
The lamp should glow for approximately 8 seconds and then turn off. Failure to turn off indica-
tes faulty protection circuit and the AVR should be replaced. Turning the "VOLTS"control
potentiometer ful ly anti-clockwise should turn off the lamp with all AVR types.
Should the lamp fail to light the AVR is faulty and should be replaced.
IMPORTANT! After this test turn VOLTS control potentiometer fully anti-clockwise.
8.5.3 REMOVAL AND REPLACEMENT OFCOMPONENT ASSEMBLIES
METRIC THREADS ARE USED THROUGHOUT
CAUTION! When lifting single bearing generators, care is needed to ensure the generator
frame is kept in the horizontal plane. The rotor is free to move in the frame and
can slide out if not correctly lifted. Incorrect lifting can cause serious injury to
personnel.
8.5.3.1 ANTI-CONENSATION HEATERS
Danger! The external mains electricity supply used to power the anti-condensation heater
must be switched off and safely isolated before attempting any work adjacent to
the heater, or removal of the non drive end bracket on which the anticon heater is
mounted. Ensure that the engine is inhibited prior to work in generator.
8.5.3.2 REMOVAL OF BEARINGS
IMPORTANT! Position the main rotor so that a full pole face of the main rotor core is at
the bottom Remove PMG of the stator bore if fitted.
The generators in this manual will be fitted with one of two different bearing arrangements.
There may be two different arrangements on a two-bearing generator.
Removal of the bearing may be effected either after the rotor assembly has been removed or
more simply by removal of endbracket (s).
Be sure to note the location of all components during removal to assist during the assembly
process.
BEARING REPLACEMENT
Environment
Every effort must be made to establish a clean area around the generator when removing and
replacing bearings. Contamination is a major cause of bearing failures.
Equipment
Suitable cleaning solvent
Bearing puller, two or three leg
Thin protective gloves
Lint free cleaning cloth
Induction heater.
Preparation
Remove the lubrication pipework if fitted .
Position the rotor so that the full pole face of the main rotor is
at the bottom of the stator bore.
Remove the end bracket, see 7.5.3.4 for procedure.
NOTES:
• It is not necessary to remove the rotor.
• Ensure that the bearing contact surface shows no sign of wear or corrosion prior to fitting the
bearing.
• Never refit used bearings, Wave washer or 'O' rings.
• Never refit used bearings, grease flinger, wave washer or 'O' rings.
• Only the outer race should be used to transmit load during assembly (NEVER use the inner
race).
REMOVAL OF REGREASABLE BEARINGS
The bearings are a press fit on the shaft and can be removed with standard tooling , i.e. 2 or 3
legged manual or hydraulic bearing pullers.
To remove bearings proceed as follows:
1. Remove 4 screws holding bearing cap.
2. Remove cap.
3. Non drive end remove wave washer and circlip (single bearing only).
4. Remove bearing cartridge housing complete with bearing (and grease f linger if fitted).
5. Remove bearing form cartridge.
6. Discard the old bearing 'O' rings and wave washer where fitted.
The bearing cap(s) and cartridge(s) must be thoroughly flushed out with clean solvent and-
checked for wear or damage, before re-assembly. Damaged components should be replaced
before refitting the bearing.
ASSEMBLY OF REASABLE BEARINGS
NOTE: Gloves must be worn at all tines when handling the bearings, grease and solvent.
1. Wipe clean the a ssembly surface, using cleaning solvent on lint free cloth.
2. Wipe clean: Bearing Cartridge. Wave Washer, Bearing Cap, greas flinger, all re-lubrication
pipes and fittings (internal and external), Visually inspect all components after cleaning, for
contamination.
3. Place all components on the clean assembly surface. Do not use an air line to blow off
excess fluid .
4. Thoroughly clean the external surface of the grease gun nozzle using lint free cloth.
Bearing preparation
1. Remove the veering from its packaging.
2. Wipe off the preservative oil from the surface of the inner and outer rings using lint free cloth
only.
3. Place the bearing on the clean assembly surface, with the bearing designation marking
facing down.
Bearing Assembly (Lubrication, see TABLE 17)
Cartridge:
1. Apply the specified cartridge grease fill quantity to the back face of the bearing housing.
2. Apply a small amount of grease to the grooved sealing surface in the bearing housing.
3. Apply anti-fretting lubricant (MP14002-Kluber Altemp Q NB 50) to the beating housing
circumference. Apply paste in a thin coherent layer by use of a lint free cloth (DO NOT rub in)
(use clean protective gloves).
4. Non-drive end fit new 'O' Rings into the 'O' Ring grooves in the bearing housing circumfe-
rence.
Bearing
84
1. Apply half the specified bearing grease fill quantity (see table 16) to the upper face of the
bearing (opposite side to the bearing designation markings).
2. Thumb the applied grease into the bearing, ensuring good penetration into the raceways/-
balls (use clean protective gloves).
Assemble Bearing into Cartridge
1. Heat the bearing cartridge to 25°C above ambient with an induction heater (Do not exceed
100°C)
2. With greased face of the bearing facing the cartridge bore, assemble the bearing into the
bearing housing. Ensure the bearing outer race contacts the location shoulder.
Assemble Bearing onto Shaft
Bearing Cartridge
1. Heat the Bearing and Cartridge assembly to ao·c above ambient with an induction heater.
(use induction heater,no other heat source is suitable)
2. Slide the Bearing and Cartridge assembly to over the shaft, pushing it firmly against the
bearing seating shoulder.
3. Rotate the assembly (including inner race) 45°C in either direction, to provide correct align-
ment. The bearing must be held firmly in place until I s cool enough to positively locate.
NOTE: Ensure cartridge is at ambient temperature before assembling bracket.
Cap/ Flinger:
Apply the specified cap grease fill quantity to the I nside face of the cap (see table 16).
1. Fill the grease exhaust slot with grease.
2. Apply a small amount of grease to the grooved sealing surface in the cap.
3. Fit circlip. (single bearing only).
4. Heat flinger to 12o·c an place on shaft up to the bearing inner race. Hold firmly until positi-
vely located.
5. Place wave washer in cap, fit cap to bearing cartridge.
REMOVAL OF SEALED FORLIFE BEARINGS
With Bearing Cartridge
The bearings are a press fit on the shaft and can be removed with standard tooling, i.e. 2 or 3
egged manual or hydraulic bearing pullers.
To remove bearings proceed as follows:
1. Remove 4 screws holding bearing cap.
2. Remove cap.
3. At the end, remove wave washer and circlip (single bearing only).