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FAULT FINDING MANUAL
For Self Excited and Separately Excited Generators




SAFETY PRECAUTIONS

Before testing the generating set, read the generating set
Installation Manual, and this Fault Finding Manual, and become
familiar with it and the equipment.

SAFE AND EFFICIENT OPERATION CAN ONLY BE
ACHIEVED IF THE EQUIPMENT IS CORRECTLY
INSTALLED, OPERATED AND MAINTAINED.

Many accidents occur because of a failure to follow fundamental
rules and precautions.

ELECTRICAL SHOCK CAN CAUSE SEVERE
PERSONAL INJURY OR DEATH.

Ensure installation meets all applicable safety and local
electrical codes. Have all installations performed by qualified
Installation technicians.

Do not operate the generator with protective covers, access
covers or terminal box covers removed.

Disable engine starting circuits before carrying out
maintenance.

Disable closing circuits and/or place warning notices on any
circuit breakers normally used for connection to the mains or
other generators, to avoid accidental closure.

Observe all IMPORTANT, CAUTION, WARNING, and DANGER
notices, defined as:

Important ! Important refers to hazard or unsafe method
or practice, which can result in product
damage or related equipment damage.

Caution ! Caution refers to hazard or unsafe method or
practice, which can result in product damage
or personal injury.




Warning refers to a hazard or unsafe method
or practice, which CAN result in severe
personal injury or possible death.





Danger refers to immediate hazards, which
WILL result in severe personal injury or
death.








Due to our policy of continuous improvement, details in this manual which were
correct at time of printing, may now be due for amendment. Information included
must therefore not be regarded as binding.
TESTING "LIVE" EQUIPMENT





It is essential that all test instruments are
regularly checked for safety, and any
connection leads, probes, or clips, are

checked to ensure that they are suitable for
the voltage levels being tested.

Never attempt to test a "LIVE" generator
unless there is another competent person
present who can switch off the power supply
or shut down the engine in an emergency.

Never expose "LIVE" connections unless you
have created a safe working area around you.
Make sure you have made all other persons in
the immediate area fully aware of what you
are doing.


3


FAULT FINDING MANUAL



















SECTION 1
Recommended Metering and Test Instruments

SECTION 2
Electrical Terminology

SECTION 3
Fault Finding method A, for All Generators

SECTION 4
Fault Finding method B, for Self-Excited Generators.
Automatic Voltage Regulator is powered from the Generator Output.

SECTION 5
Fault Finding method B, for Separately Excited Generators
Automatic Voltage Regulator is powered from the Permanent Magnet Generator.

SECTION 6
Parallel Operation and Fault Finding for All Generators


4
SECTION 1

RECOMMENDED METERING AND TEST INSTRUMENTS


To successfully carry out the various test procedures suggested
in this manual, certain test instruments are essential. The
following lists detail the basic requirements in this respect.

It should be noted that in addition to these instruments a
comprehensive kit of tools is also essential. For fault finding
purposes this need not include any specialised tools.

Item 1 - Multimeter

The Multimeter is a comprehensive test instrument for measuring
voltage, current and resistance. It should be capable of
measuring the following ranges:-

Voltage A C
0-250-500-1000 Volts
Voltage D C
0-25-100-250 Volts
Amperes D C
0-10 Amps
D C Resistance
0-10k (ohms) or 0-2k (ohms)

0-100k (ohms) or 0-20k (ohms)

0-1M (ohms) or 0-200k (ohms)

Item 2 Tachometer or Frequency meter

This instrument is for measuring the shaft speed of the alternator
and should be capable of measuring speeds between 0 and 5000
revolutions per minute, (RPM).

An alternative to the tachometer is the frequency meter (see
Section 2 on Frequency and Speed, for details). However the
alternator must be generating its normal output voltage for this
instrument to be accurate.

Item 3 Megger (Insulation test meter)

This instrument generates a voltage of 500V or 1000V, and is
used to measure the resistance value of the insulation to earth
(ground). It may be an electronic push button type, or a hand
cranked generator type.

Item 4 - Clip-On Ammeter (Clampmeter)

Used to measure A C current, it consists of a pair of callipers,
which are clamped around the conductor, and by means of a
transformer action, gives an indication of the amperes flowing in
the conductor. Useful ranges to have on this meter are:-

A C Amps 0-10-50-100-250-500-1000

Item 5 Kelvin Bridge low resistance meter

This instrument is used to measure resistance values below 1.0
ohm. They are bulky, and expensive, but are the only means of
accurately measuring very low resistances, such as main stator
and exciter rotor windings.
However, there are other methods of testing low resistance
windings, and these are included in the various test procedures,
i.e. Test Method A (Section 3). This section will enable the main
generator windings to be tested while running the generator at
normal speed without load.









It is essential that all test instruments be
regularly checked for safety, and any
connection leads, probes or clips checked to
ensure that they are suitable for the voltage
levels being tested.

Never attempt to test a "LIVE" generator
unless there is another competent person
present who can switch off the power supply
or shut down the engine in an emergency.

Never expose "LIVE" connections unless you
have created a safe working area around you.
Make sure you have made all other persons in
the immediate area fully aware of what you
are doing.




MEDIUM/HIGH VOLTAGE
3.3 kVA to 11.0 kVA

Do not attempt to carry out tests on medium
or high voltage generators without using
specialised instruments and probes, with
suitable protection equipment and
procedures for grounding (earthing) the
output terminals.

5
SECTION 2

ELECTRICAL TERMINOLOGY AND RESISTANCES
VOLTAGE AND CURRENT (AMPERES)


An AC Generator is designed to produce a voltage level suitable
for the load to which it is connected. The control circuits are
designed to automatically maintain this voltage level as the load
is increased or decreased.

Sudden large changes in loading will produce temporary changes
in the voltage. The control circuit is designed to recover to a
stable condition as quickly as possible.
The current drawn from the AC Generator is determined by the
amount of load connected to it. Current creates a temperature
rise in the windings, hence the requirement for drawing air
through the AC Generator by means of the fan. If the full load
rated current is exceeded on any phase of the main stator
windings, it will result in overheating in this winding. Similarly, any
restriction in the flow of air through the machine will result in a
rapid increase in the temperature of the windings.

Frequency (Hz) and Speed (RPM)

An AC Generator is a constant speed device, and should not be
operated at speeds above 4% of the rated speed, or more than
1% below the rated speed.

Load changes will create temporary changes in the speed, but
the engine must be capable of returning to the steady state
condition within a few seconds.

The speed requirements for the AC Generator are determined
by:-

(a) The frequency (Hz) requirement of the load
(b) The number of poles,( main rotor coils), in the generator


Frequency (HZ) =

This can be shown more clearly in a chart: -


Frequency (Hz)
Speed (R.P.M.)
No. of Poles
(rotor coils)
50 1500 4
60 1800 4
50 1000 6
60 1200 6
50 3000 2
60 3600 2

From this chart, a simple formula is produced to calculate the
speed from the frequency, or vice versa.

4 pole machine
1 cycle (Hz) = 30 R.P.M.
6 pole machine
1 cycle (Hz) = 20 R.P.M.
2 pole machine
1 cycle (Hz) = 60 R.P.M.

Kilowatts (kW) kilo Volt Amperes (kVA) and Power
Factors (pf.)

For an AC Generator to supply power for a load of 1kW, the
prime mover (engine)