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ODP generators
Model MJH
Power Up to 12.500 kVA
Voltages Up to 15.000 V
Frame 400 ± 1.250
Pole 4, 6, 8, 10 and 12
(over contact MM)
Cooling IC 01
IP IP 23. Available up to IP 44 with filters.
Main Applications PRP and COP, Stand-by, Emergency, UPS, Portable
Poles (kVA 60 Hz)


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 1.22
Generators conform to EU rules.
UL/CSA certifications available on request.
Aderence to ISO 8528 group G preformance classes.
Test Certificate supplied with the machine.
Material certificates in accordance with EN 10204 : 2001 can be supplied.
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 – TN).
Shaft is obtained by forging from 290 mm diameter and above.
The shaft is tested to ensure defect-free performance.
Shaft design
Double bearing generator: cylindrical shaft with key.
Main terminal box
Mounted on top.
Made of formable steels EN 10130.
Made of aluminum alloy (EN 1706) or structural steel (EN 10025–S235 JR) depending on application requirements.


ODP - Open Drip Proof
Cooling System
IC 01 as per IEC60034-6
Degree of protection
IP 23 as per IEC60034-5
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 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: F class insulated with a synthetic enamel
Rotor: H class insulated with a synthetic enamel
Protective treatments
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 ratings
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 3 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.
Size Type
400 - 450 MEC 20 analog/ digital
500 - 560 M40FA610A analog
630 - 710 M63FA310A analog
800 - 1250 MEC 100 digital
Digital AVR available for all sizes on request.
Overboosting device
Size Type
Medium Voltage All CT + Overboosting device
High voltage All PMG
Space heaters
Heaters installed at ND-end side.
Size Power(W)
400 - 560 400
630 - 710 600
800 - 900 800
1000 1000
1120 1200
1250 1400
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
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
  • increase protection degree up to IP 44 with filters
  • 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.