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Motor & Alternator Expert Service

RotoTech provides comprehensive overhaul, maintenance and repair solutions for motors, alternators and generators, ensuring maximum uptime and reliability for your rotating equipment.

2,350 kVA: Alternator rotors rewound, five in one order
5,000 kg: Rotor balancing capacity for generators and large motors
8: Electrical tests in our own test bay
24/7: Emergency support

Motors & alternators

What we do

Stator and rotor rewinding: complete rewinding solutions that restore electrical performance to OEM specifications
Dry ice cleaning and PD (partial discharge) repair: non-abrasive cleaning combined with expert PD repair for windings and insulation systems
Shaft journal and bearing housing repair: precision restoration of worn or damaged journals and housings to original tolerances
Casing crack repair: structural repair of cracked motor and generator casings using proven industrial welding and reinforcement techniques
Shaft runout correction: accurate diagnosis and correction to restore rotational integrity
Vibration analysis and rotor balancing: advanced diagnostics paired with precision balancing for smooth, efficient operation
Laser alignment: high-precision shaft alignment to minimize vibration and extend equipment life
Bearings and spare parts supply: genuine and compatible bearings and components for scheduled overhauls and emergency breakdown maintenance

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Rotor insertion into a Leroy-Somer alternator

Electrical services

One electrical team

For the machines that generate and use power, in our Savar workshop and at your site.

Workshop & site
Motors & alternators
Regular maintenance, rewinding, dynamic balancing, bearing housing repair and insulation testing. Local representative of New Standard Electrical.

Overhaul

A standard overhaul, step by step

Every motor and alternator we overhaul goes through the same sequence, whether it arrives for planned maintenance or after a breakdown. Each step finds or removes a cause of failure before the machine goes back into service.

Inspection after dismantlingEvery component examined for wear, damage and fatigue.

Tests and calibrationMagnetic particle inspection (MPI), shaft and bearing housing calibration, insulation resistance, polarization index and surge tests.

Dynamic balancingThe rotor balanced to ISO 21940 on our own machines.

Varnishing and bakingA protective varnish on the windings, cured in the oven for durable insulation.

ReassemblyRebuilt to the maker's assembly procedures and specifications.

Run testA final run test, at your site where needed, to prove performance under real conditions.

Lifting and positioning on a generator overhaul
Bearing-end work on a generator
Stator winding inspection
Bearing-end assembly with a torque bar
Inspection inside a generator stator
Salient-pole alternator rotor

Rewinding

Rewound to OEM electrical specification

Our rewinding setup restores burnt-out or ageing motor and alternator windings, stator and rotor, so the machine performs to its original electrical specification again.

Five 2,350 kVA alternator rotors

Five alternator rotors rated 2,350 kVA at 480 V, rewound with imported double-layer enamel-coated, H-class insulated copper strip (flat wire), and delivered in two and a half months.

For Lafarge Holcim, an ABB 355 kW special-type motor received a complete stator rewind, rotor balancing, calibration of the bearing journals and housings and MPI, and passed the end user's test run.

Winding data recorded
New coils made to that data
Wound with class F or H insulation
Varnished and cured in the oven
Assembled and tested

Why the oven must heat evenly

Even Curing: Ensures the varnish or insulation cures properly. Uneven heating can lead to incomplete curing and insulation failures.
Prevents Hot Spots: Avoids localized overheating that can damage insulation and reduce the motor’s lifespan.
Proper Bonding: Ensures varnish or insulation bonds well, preventing weak spots.
Reduces Stress: Prevents warping and mechanical stress from uneven heating.

What it gives you

Improves Efficiency: Guarantees correct insulation properties, enhancing performance.
Maintains Quality: Ensures consistent quality and reliability of the finished product.
Stator and rotor rewinding: complete rewinding solutions that restore electrical performance to OEM specifications

Electrical testing

Verified before it leaves

Every machine is verified through our electrical testing facility before it goes back to you, and the readings go into the job report.

Insulation resistance (IR) test
Winding resistance test
Polarity test
Impedance test
Surge comparison test
High voltage test
Core loss test
Polarization index (PI) test

Electrical testing facility

Winding resistance test
Winding resistance test
Winding resistance test
Insulation resistance test
Impedance test

Mechanical repair

Journals, housings and balance

Many electrical failures start as mechanical ones: a worn bearing housing, a damaged journal, a rotor out of balance. We rebuild them to their original dimensions and balance the rotor, so the windings are not damaged again.

7×unbalance found in the rotor

200–300 HBjournal surface hardness

2,100 kgrotor balanced to ISO 21940

1,875 kVA Marelli alternator rotor

The rotor's bearing journal had been damaged when its bearing seized, and the cause was an unbalance seven times too high. We rebuilt the journal in a tough, fatigue-resistant medium-carbon alloy to a Brinell hardness of 200–300 HB and the required surface finish, checked it by magnetic particle testing, then balanced the 2,100 kg rotor to ISO 21940.

Bearing housing repair

01Find the cause of wearDimensional calibration checks and material hardness tests.

02Rebuild and machineBack to the original dimensions, to a three-digit accuracy level.

03Prove it with MPIMagnetic particle inspection finds hidden cracks in stress-prone areas.

Why RotoTech

One partner for the whole machine

What you gain

Maximum uptime and reliability
Fast support for both scheduled overhauls and emergency breakdowns
Repairs restored to original tolerances and OEM electrical specifications
Smoother, more efficient running with less vibration
One partner for mechanical repair, electrical repair and testing

Also from RotoTech

New ABB motors
Troubleshooting at site, from alignment issues to burnt-out windings
Bearings and spare parts supply: genuine and compatible bearings and components for scheduled overhauls and emergency breakdown maintenance
Local representative of New Standard Electrical

FAQ

Frequently Asked Questions

Do you service motors and alternators?

RotoTech provides end-to-end maintenance solutions, including regular maintenance, motor and alternator rewinding, dynamic balancing, and bearing housing refurbishment. Every machine is verified through our extensive electrical testing facility, and we execute scheduled maintenance projects directly at your site.

Do you rewind stators and rotors?

Stator and rotor rewinding: complete rewinding solutions that restore electrical performance to OEM specifications

Which electrical tests do you carry out?

Insulation resistance (IR) test
Winding resistance test
Polarity test
Impedance test
Surge comparison test
High voltage test
Core loss test

Can you repair cracked casings and worn journals?

Casing crack repair: structural repair of cracked motor and generator casings using proven industrial welding and reinforcement techniques
Shaft journal and bearing housing repair: precision restoration of worn or damaged journals and housings to original tolerances

Do you handle emergency breakdowns?

Fast support for both scheduled overhauls and emergency breakdowns
Bearings and spare parts supply: genuine and compatible bearings and components for scheduled overhauls and emergency breakdown maintenance