Model MJV

Power Up to 4.550 kVA

Voltages Up to 690 V

Frame 250 ± 900

Poles 4, 6, 8, 10 and 12 (over contact MM)

Cooling IC 611

IP IP 55. Available up to IP 56.

Enclosure TEAAC – Totally Enclosed Air to Air Cooled

Main Applications Auxiliary generators, Emergency, Power generation

Sector Oil&Gas

Poles Header
4 3.500
6 4.550
8 4.550
10 4.550
12 4.000

Certificates and testing

Applicable standards

Generators are designed in compliance with:
IEC EN 60034 - 1
BS 4999 - 5000
VDE 0530
NF 51 - 100
NF 51 - 111
OVE M - 10
NEMA MG 1.32
Generators conform to EU rules.

UL/CSA certifications available on request.
Adherence to ISO 8528 group G preformance classes.

Main components


Rigid frame, rugged welded steel fabrication (EN 10025 - S235 JR).
Frame is provided with side ribs to increase the strength.
Marelli Generators for continuous duty operation are designed to meet vibration levels per IEC 60034-14, ISO 10816-1 and BS 5000-3.


Made of spheroidal graphite cast-iron (EN 1563) or grey cast-iron (EN 1561) up to 630 frame size.
Made of structural steel (EN 10025 – S235 JR) above.


General data
Made in carbon steel and obtained by lamination (EN 10083 – 2 C40 – N).
Shaft is obtained by forging from 290 mm diameter and above.
The shaft is tested at the manufacturer in order to check it is defect-free.
Shaft design
Double bearing generator: cylindrical shaft with key.

Main terminal box

Mounted on side (right or left will be selected).
Made of formable steels EN 10130.


Made of aluminum alloy (EN 1706) or structural steel (EN 10025–S235 JR) depending on application requirements.

Internal Fan

Made of structural steel (EN 10025 - 5235 JR)

Heat Exchanger


  • Mounted on top of alternator
  • Tube made of P - AIMgSi UNI 3569
  • Housing: EN 10025 - 5235JR


Cooling System

IC 611 as per IEC60034-6. Primary fluid (air) driven by a second fan (internal fan) mounted on shaft at ND end side. Internal air is flowing by a fan mounted on the shaft of the generator at the driven side.

Operating temperature

Up to 60° C ambient temperature (over contact Marelli Motori)

Degree of protection

IP 55 as per IEC60034-5. Other protection degree available on request.


Horizontal - IM 1001 or IM 1101 as per IEC 60034-7. Other mounting available on request.

Technical data

Stator/Rotor core

Laminated and enamel-insulated on both sides to minimise eddy-current losses


Salient pole type.
Made by copper flat wire.
H class insulated with enamel coating.
Winding retaining by pass-through bars of high quality steel.
Rotating rectifier: Graetz diode bridge with 6 diodes.
Rotors are dynamically balanced with a half key applied to the shaft extension in accordance with IEC 60034-14 to vibration grade normal A.
Special vibration level construction are available.


General data
Single or double antifriction bearing grease lubricated (ball or roller type) or oil lubricated sleeve bearing.
The theoretical lifetime of bearings, L10h according to ISO 281/1 standard, of standard horizontal construction generators, without external forces (radial and / or axial) is in excess of 50.000 hours. On request, the lifetime of bearings, L10h can be in excess of 100.000 hours. Locating bearings are on the D end side and floating bearings on the ND end side. 
Bearing selection
Antifriction bearings up to 800 frame size included. Sleeve bearings from 900 frame size included (available for smaller frame sizes).
Regreasing system:
Up to 250 frame size:

  • D-end bearing is prelubricated with inner bearing cap and without grease nipple
  • ND-end bearing is with shield (2Z) without regreasing system

315 - 355 frame size:

  • D-end bearing is fitted with inner bearing cap and with gerase nipple
  • ND-end bearing is with shield (2Z) without regreasing system

400 frame size:

  • D-end bearing is fitted with inner bearing cap and with gerase nipple
  • ND-end bearing is prelubricated with inner bearing cap and without grease nipple

450 frame size and above: both bearings are fitted with grease nipple.
Bearing insulation
ND end bearing can be insulated to prevent any harmful circulating current from passing through the bearing surfaces. Insulated antifriction bearings in standard configuration:

  • 4, 6 poles: insulated ND end bearing from 630 frame size
  • 8 poles: insulated bearing from 400 frame size
  • 10 poles: insulated bearing from 500 frame size

All ND end sleeve bearings are insulated as standard.

Impregnation system

Stator and rotor are VPI treated with an unsaturated polyester amide resin which is polymerised in an oven.

Insulation system

Stator: H class insulated with a synthetic enamel (class F standard for generators with H>=800 or form wound form H=400. Class H option with BH technology).
Rotor: H class insulated with a synthetic enamel.

Protective treatments

Specific Oil&gas treatment.
Epoxivinilic and polyacrylic. Total minimum thickness 120 micromillimeters.
Epoxivinilic: Epoxy two component products, with vinyl change
Polyacrylic: Two components polyurethane product formulated with unmodified hydroxyl acrylic resin.

Operating conditions


During continuous duty (S1), the following overloads are allowed:
10% for 1 hour
15% for 10 minutes
30% for 4 minutes
50% for 2 minutes
These overloads must be occasional and followed by one hour of running at normal load or less.

Parallel operations

All generators are provided with a amply sized damper cage and are suitable for parallel operations with other generators, when equipped with the paralleling unit. A power factor regulator (to work in parallel with the main) is available on request.

Transient performance

All generators can be designed to meet specific reactance values (x'd and x''d). Values can be confirmed by contacting Marelli Motori.

Three pahse short circuit current

All generators equipped with overboosting device ensure a three phase short circuit current (Icc) higher than three times the rated current (In): Icc > 300% In

Radio interference

All generators are equipped with Class B Group 1 radio interference filters as defined by EN 55011.

THD (Total Harmonic Distortion)

The no-load voltage wave form is sinusoidal with THD content less than 2%.


Vibration level is in accordance with ISO 10816. Measurement, evaluation and limits of vibration severity are in accordance with IEC 60034-14.

Auxiliary device


Automatic voltage regulator mounted on board.





MARK V analog


315 - 450

MEC 20 analog/ digital


500 - 560

M40FA610A analog


630 - 710

M63FA310A analog


800 - 900

M63FA310A analog


Digital AVR available for all sizes on request.


Overboosting device

Low voltage




Low voltage

250 - 450 (4 poles)

Auxiliary winding


400 - 450 (>4 poles)



500 - 710 (all polarities)



800 - 900


PMG available for all sizes on request.


Space heaters

Heaters installed at ND-end side.




400 - 560



630 - 710



800 - 900




RTD devices in standard configuration:

  • 1+1 RTD on each phase of stator winding
  • 1 RTD on each bearing

Terminals in auxiliary terminal box. Other configurations available:

  • DUPLEX type
  • RTD for inlet / outlet air
  • RTD into oil tank for sleeve bearing

Optional features

  • Flanged shaft for direct coupling with engine flywheel (in case of single bearing solution)
  • neutral point terminals in separate terminal box
  • dedicated current transformer installed on neutral point (differential protection and measurement)
  • cooling system IC 616 with additional forced ventilation
  • increase protection degree up to IP 56 with filters
  • dedicated lubrication unit for sleeve bearing solution
  • lifted feet to couple the generator with engine on existing baseframe
  • redundant rotating rectifier with 12 diodes
  • insulated bearing and earthing brush
  • AVR supplied loose
  • automatic power factor control (analog type or included into digital regulation)
  • digital AVR MEC100 for frame 250 – 710 (supplied loose)
  • digital AVR MEC100D with diode failure monitoring
  • other digital AVR available on request
  • redundant AVR system
  • excitation/overboosting PMG mounted on generator
  • arrangement for earthing rotor fault protection 64R
  • other options available on request.