Model MJRM

Power Up to 6.500 kVA

Voltages Up to 690 V

Frame 250 ± 900

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

Cooling IC 81W/ IC 86W

IP IP 44. Available up to IP 56.

Enclosure TEWAC - Totally Enclosed Water to Air Cooled.

Main Applications Auxiliary generator, Hybrid machine, Off-shore and variable speed generator, Propulsion generator, Shaft generator

Sector Marine

Poles kVA 60 Hz
4 4.000
6 5.000
8 6.500
10 6.000
12 5.400

Main components


 Rigid frame, rugged welded steel fabrication (EN 10025 - S235 JR). 
Frame is provided with side ribs to increase the strength. 
Marelli Motori 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–TN). 
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 upon application requirments.

Heat Exchanger

Mounted on top of alternator. 
Double tube made of CuNi 90/10. 
Copper fins housing. 
Equipped with water leakage detector. 
Exchanger data

  • Designed pressure 6 bar
  • test pressure 10 bar
  • power: up to 200 kW
  • water flow: up to 18 m3/h
  • max glycol: 30%
  • type of water: fresh water or marine (salt) water
  • flanges:
  • PN6 – PN10 – Special (ANSI)
  • Position can be adjusted to site conditions.


Cooling System

 IC 81W as per IEC60034-6. Primary fluid (water) is flowing by external water system. Internal air is flowing by a fan mounted on the shaft of the generator at the driven side.

Degree of protection

 IP 44 as per IEC60034-5. (Available up to IP 56)


 Horizontal - IM 1001 or IM 1101 as per IEC 60034-7

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 is 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 560 frame size included. 
Sleeve bearings from 630 frame size included (available for smaller frame sizes). 
Antifriction bearings can be mounted on 630/710 frame size according to site working conditions. 
Regreasing system (for antifriction bearing)
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. All configurations are designed to withstand the following marine inclination.


List 15°

Trim 5°


Rolling ±22.5°
Pitch ±7.5°


Dedicated constructions available for different values.

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 marine 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 an 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 ratings

 All generators comply with marine rules regarding transient performance. The voltage drop due to the application of 60% of nominal load is within 15%.

Three pahse short circuit current

 All generators equipped with an 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

MEC 100 digital

Overboosting device




Low voltage

250 - 450 (4 poles)

Auxiliary winding


400 - 450 (>4 poles)



500 - 710 (all polarities)



800 - 900


Space heaters

 Heaters installed at ND end side.


Power (W)





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 for inlet / outlet water

Optional features

  • Reinforced construction for high linear vibrations
  • flanged shaft for direct coupling with engine flywheel (in case of single bearing solution)
  • neutral point terminals in separate terminal box
  • terminal box inside air duct (internal terminal box)
  • cooling system IC 86W with additional forced ventilation
  • cooler mounted on side
  • increase protection degree up to IP 54, IP 55 or IP 56
  • 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)
  • digital AVR MEC100 for frame 400 – 710 (supplied loose)
  • digital AVR MEC100D with diode failure monitoring
  • redundant AVR system
  • excitation/overboosting PMG mounted on generator
  • lubrication system for sleeve bearing
  • other options available on request.

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.


 Marine Survey Certificate supplied with the machine. 
Marelli Motori has the ABS design assessment. 
Shaft, housing (propulsion) and exchanger are certified by the Marine Classification Society.