MJRT

ModelMJRT
PowerUp to 5.000 kVA
VoltagesUp to 690 V
Frame250 ± 900
PolesFrom 4 to 20 poles (over contact MM)
CoolingIC 81W / IC 86W
IPIP 44. Available up to IP 56.
EnclosureTEWAC - Totally Enclosed Water to Air Cooled
Main ApplicationsCross-Flow turbines, Francis turbines, Kaplan turbines, Pelton turbines, Turgo turbines
SectorHydropower
  • Certificates and testing
  • Main components
  • Construction
  • Technical data
  • Operating conditions
  • Auxiliary device
  • Optional features

Certificates and testing

Applicable standards
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.
Certificate
Certificate
Test Certificate supplied with the machine. Material certificates in accordance with EN 10204 : 2001 can be supplied.

Main components

Housing
Housing
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.
Shield
Shield
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.
Shaft
Shaft
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. Dedicated shaft design available on request. Special shaft design for direct coupling with runner are available on request.
Main terminal box
Main terminal box
Horizontal - IM 1001 or IM 1101 as per IEC 60034-7. Vertical IM 3011 as per IEC 60034-7 Other mounting available on request.
Fan
Fan
Made of aluminum alloy (EN 1706) or structural steel (EN 10025–S235 JR) depending on application requirements.
Heat Exchanger
Heat Exchanger
Construction
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
  • Flanges:
  • PN6 – PN10 – Special (ANSI)
  • Position can be adjusted to site conditions

Construction

Enclosure
Enclosure
TEWAC - Totally Enclosed Water to Air Cooled
Cooling System
Cooling System
IC81W 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
Degree of protection
IP 44 as per IEC60034-5. (Available up to IP 56)
Mounting
Mounting
Horizontal - IM 1001 or IM 1101 as per IEC 60034-7. Vertical IM 3011 as per IEC 60034-7 Other mounting available on request.

Technical data

Stator/Rotor core
Stator/Rotor core
Laminated and enamel-insulated on both sides to minimise eddy-current losses
Rotor
Rotor
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.
Bearing
Bearing
General data
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 900 frame size included depending on nominal speed, overspeed and mechanical load on the shaft.
Sleeve bearings available from 400 frame size.
Regreasing system:
Generators in horizontal mounting and equipped with antifriction bearing include a regrasing system.

 xANTIFRICTION BEARINGSSLEEVE BEARINGS
 xHORIZONTAL MOUNTINGVERTICAL MOUNTINGHORIZONTAL MOUNTINGVERTICAL MOUNTING
AVAILABLE LUBRICATION
TYPE D-END / ND-END
BOTH GREASE WITH REGREASING SYSTEMBOTH GREASE WITH REGREASING SYSTEMBOTH NATURAL OIL LUBRICATEDBOTH NATURAL OIL LUBRICATED
D-END: GREASE WITH REGREASING SYSTEM
ND END: OIL WITH OIL REFILL SYSTEM
(ONLY FOR SPECIAL LOW SPEED CONSTRUCTION)
D-END: GREASE WITH REGREASING SYSTEM
ND END: OIL BATH OIL REFILL SYSTEM
BOTH OIL FORCED LUBRICATEDBOTH OIL FORCED LUBRICATED
AVAILABLE LUBRICATION
TYPE D-END / ND-END
NATURALNATURALNATURAL LUBRICATED ARE COOLED BY WATER
OIL FORCED LUBRICATED ARE COOLED BY AN EXTERNAL OIL LUBE SYSTEM

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 and above: insulated bearing from 500 frame size
All ND end sleeve bearings are insulated as standard.
Impregnation system
Impregnation system
Stator and rotor are VPI treated with an unsaturated polyester amide resin which is polymerised in an oven.
Insulation system
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
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

Overloads
Overloads
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
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
Transient ratings
All generators can be designed to meet specific SCR. Values can be confirmed by contacting Marelli Motori.
Three pahse short circuit current
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
Radio interference
All generators are equipped with Class B Group 1 radio interference filters as defined by EN 55011.
THD (Total Harmonic Distortion)
THD (Total Harmonic Distortion)
The no-load voltage wave form is sinusoidal with THD content less than 2%.
Vibrations
Vibrations
Vibration level is in accordance with ISO 10816. Measurement, evaluation and limits of vibration severity are in accordance with IEC 60034-14.
Inertia
Inertia
All generators can be designed to meet specific inertia value also through flywheel. Values can be confirmed by contacting Marelli Motori.

Auxiliary device

AVR
AVR
Automatic voltage regulator mounted on board.
SizeType
250MARK V analog
315 - 450MEC 20 analog/ digital
500 - 560M40FA610A analog
630 - 710M63FA310A analog
800 - 900MEC 100 digital
Digital AVR available for all sizes on request.
Overboosting device
Overboosting device
Low voltage
SizeType
Low voltage250 - 450 (4 poles)Auxiliary winding
400 - 450 (>4 poles)Varicomp
500 - 710 (all polarities)Varicomp
800 - 900VARICOMP
Space heaters
Space heaters
Heaters installed at ND-end side.
SizePower(W)
400 - 560400
630 - 710600
800 - 900800
RTD-PT100
RTD-PT100
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

List
List
  • Reinforced construction for high linear vibrations
  • flanged shaft for direct coupling with runner
  • neutral point terminals in separate terminal box
  • increase protection degree up to IP 44 with filters
  • dedicated design to couple the generator with existing baseframe
  • air duct system to convey inlet / outlet cooling air
  • 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
  • arrangement for vibration sensors
  • lubrication system for sleeve bearing
  • flywheel and locking device for dedicated inertia value
  • brake system
  • other options available on request.

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