Excitation, Rotors & Stators

Newton Derby is a long established manufacturer of exciters, generators and associated products.

Newton Derby has an extensive client base in the UK and worldwide. Clients include the Ministry of Defence, rail and power generation companies, as well as a host of overseas military facilities.

They are a main supplier of special Exciter Machines to the world’s major manufacturers of large Synchronous Generators and Motors, and produce various forms of Exciter Machines depending on the individual requirements of our customers.

Newton Derby prides itself on the quality of its design and development skills, enabling the company to offer special equipment for the most demanding applications, in addition to its established product range. Exciters are usually provided as Stator/Rotor units for mounting within the enclosure of the main generator/motor.

The Exciter Rotor has an internal bore suitable for fitting to the shaft of a large synchronous machine, usually by means of a shrink fit and key.
  • Stator housings and mounting arrangements are designed for individual applications. These can incorporate Foot or Flange Mounting as required, or can be supplied entirely without housing.
  • A Vacuum and Pressure Impregnation Process for the rotors, combined with a High Integrity Class F insulation system ensures excellent reliability and long insulation life in the most hostile industrial, marine and military environments.
  • All rotors are designed to withstand 20% over-speed for a period of 2 minutes.

Newton Derby offer a full design service and produce bespoke designs for most customers.  However in some cases, they offer a build-to-print service manufacturing to the customer’s design and drawing package.

Optional Equipment

In their simplest form, exciters are produced as basic stator/rotor units but a wide range of optional extras are available. Some of our customers opt for a fully comprehensive service where the Exciter Machine is supplied as a self-contained machine, incorporating a variety of optional equipment and features including:

  • Earth Fault Detection Slip Rings & Brush Gear
  • Brush Lifting Actuator
  • Shaft Seals
  • PMG Pilot Exciter
  • Anti-condensation Heaters
  • Rotating Rectifier Assembly
  • Self Contained Air Cooling System with Internal Fan and Ducting
  • Split Stators to ease maintenance


Newton Derby manufactures a large range of sizes of Excitation Machines, and is capable of creating a bespoke design to suit most requirements.
Rotating Rectifiers

The rotating rectifier with surge protection is one of many available options. Rotating rectifiers are produced with ceiling ratings in excess of 2000 amps DC. The rectifier bridge is also protected against overvoltage spikes by a Voltage Dependent resistor and suppressor assembly.

All diodes are mounted and clamped to withstand the rotational forces and are rated for the continuous and ceiling output power required by the main generator field system. Balancing slots are an optional feature of rotating rectifier units.

Newton Derby’s sales and design team are ready and able to assist with your specific requirements for quality assured products in accordance with Newton Derby’s ISO 9001 Quality approval.


  • Power Generator
  • Oil & Gas
  • Renewable Energy

Permanent Magnet Pilot Exciters

A PMG can be incorporated into the Exciter Machine if required by the customer.

  • PMGs can be supplied as Stator/ Rotor units, or as fully enclosed auxiliary machines.
  • PMGs are designed incorporating either Alnico or Rare Earth type magnets depending on the application and specifications.

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