Mosa GE 225 VPS Instruction Manual Download Page 25

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Using the generator

1.1-09/05

12/06/03 M37GB_1500G_GE

WARNING

Access forbidden to area adjacent to
electricity-generating group for all non-
authorized personnel.

It is absolutely forbidden to connect the unit
to the public mains and/or another electrical
power source .

GE_
Diesel engine

The electricity-generating groups are to be considered
electrical energy producing stations.
The dangers of electrical energy must be considered
together with those related to the presence of chemical
substances (fuels, oils, etc.), rotating parts and waste
products (fumes, discharge gases, heat, etc.).

GENERATION IN AC (ALTERNATING CURRENT)

Before each work session check the efficiency of the
ground connection for the electricity-generating group if
the distribution system adopted requires it, such as, for
example, the TT and TN systems.

Check that the electrical specifications for the units to
be powered - voltage, power, frequency - are compatible
with those of the generator. Values that are too high or
too low for voltage and frequency can damage electrical
equipment irreparably.
In some cases, for the powering of three-phase loads, it
is necessary to ensure that the cyclic direction of the
phases corresponds to the installation’s requirements.

Connect the electric devices to be powered to the AC
sockets, using suitable plugs and cables in prime
condition.

Before starting up the group, make certain no dangerous
situations exist on the installation to be powered.
Check that the thermal-magnetic switch (Z2) is in the
OFF position (input lever in downward position).

Start up the electricity-generating group, positioning the
thermal-magnetic switch (Z2) and differential switch (D)
to ON (input lever in upward position).
Before powering on the utilities, check that the voltmeter
(N) and frequency meter (E2) indicate nominal values;
in addition, check on the voltmeter change-over switch
(H2) (where it is assembled) that the three line voltages
are the same.

☞

In the absence of a load, the values for voltage and

frequency can be greater than their nominal values.
See sections on VOLTAGE and FREQUENCY.

OPERATING CONDITIONS

POWER

The electrical power expressed in kVA on an electricity-
generating group is the available output power to the
reference environmental conditions and nominal values
for: voltage, frequency, power factors (cos

There are various types of power: PRIME POWER (PRP),
STAND-BY POWER established by ISO 8528-1 and
3046/1 Norms, and their definitions are listed in the
manual’s TECHNICAL SPECIFICATIONS page.

☞

During the use of the electricity-generating group

NEVER EXCEED

the power indications, paying careful

attention when several loads are powered
simultaneously.

VOLTAGE
GENERATORS WITH COMPOUND SETTING.

In these types of generators, the no-load voltage is
generally greater than 3–5% with respect to its nominal
value; f.e. for nominal voltage, threephase 400Vac or
singlephase 230Vac, the no-load voltage can be
comprised between 410-420V (threephase) and 235-245V
(singlephase). The precision of the load voltage is
maintained within ±5% with balanced loads and with a
rotation speed variation of 4%. Particularly, with resistive
loads (cos

= 1), a voltage over-elevation occurs which,

with the machine cold and at full load, can even attain
+10 %, a value which in any case is halved after the first
10-15 minutes of operation.
The insertion and release of the full load, under constant
rotation speed, provokes a transitory voltage variation
that is less than 10%; the voltage returns to its nominal
value within 0.1 seconds.

GENERATORS WITH ELECTRONIC SETTING
(A.V.R.).

In these types of generators, the voltage precision is
maintained within ±1,5%, with speed variations
comprised from -10% to +30%, and with balanced loads.
The voltage is the same both with no-load and with
load; the insertion and release of the full load provokes
a transitory voltage variation that is less than 15%; the
voltage returns to its nominal value within 0.2–0.3
seconds.

FREQUENCY

The frequency is a parameter that is directly dependent
on the motor’s rotation speed. Depending on the type of
alternator, 2 or 4 pole, we will have a frequency of 50/60
Hz with a rotation speed of 3000/3600 or 1500/1800
revolutions per minute.
The frequency, and therefore the number of motor
revolutions, is maintained constant by the motor’s speed
regulation system.
Generally, this regulator is of a mechanical type and
presents a droop from no-load to nominal load which is
less than 5 % (static or droop), while under static
conditions precision is maintained within ±1%.Therefore,
for generators at 50Hz the no-load frequency can be
52–52.5 Hz, while for generators at 60Hz the no-load
frequency can be 62.5-63Hz.