Type test of the largest commercial 4-pole generator and exciter for a EPR power plant

Power Reactor, but is now simply named EPR.

For an EPR reactor, the largest commercial generator designed by Arabelle Solutions is the 2235 MVA class turbogenerator. This machine is a new model, which will be the base of further derived units for future 50 Hz EPR applications or equivalent.

The turbo generators are designed for all types of half-speed turbines for nuclear power plants

(NPP). It represents a substantial step compared to the world’s largest generators in operation in EDF nuclear fleet operating since the 1990s and the last one, Flamanville 3 (the most powerful), connected to the grid end of 2024 and other highest power nuclear units built by

Arabelle Solutions: Forsmark, Oskarshamn, Taishan.

The largest commercial 2235 MVA class turbogenerator has been delivered after comprehensive type tests in factory, which demonstrates and validates the performances of the generator and of its future evolutions.

This output has been achieved using proven and optimised technologies already used on other nuclear and fossil units.

The running tests were performed for stator voltages higher than the rated values, which constitute one of the worldwide largest powers ever running tested. The test stand of the OEM has been upgraded to enable an increase of the driving power by 40 %. The evaluation of the test results allows the overall performance of the machine to be checked.

First heat run tests confirm that the temperature rise of the different parts of the generator are in compliance with the IEC standard criteria and also conform to calculated values.

In addition to generator standard instrumentation, a large set of temporary test instrumentation was installed in order to monitor temperatures, currents, voltages, flux density, etc. The temperature of neutral and short-circuit bars were monitored with a thermal camera.

Three heat run tests were performed:

1.

Un-excited 2.

Stator winding in open-circuit and field winding excited to obtain 110 % of rated armature voltage.

3.

Stator winding short-circuited and field winding excited to obtain 100 % of rated armature current.

The measured temperatures of stator core, flux shields, stator and rotor windings were recorded and checked during the tests.

These heat run tests were also used to measure and validate the predicted efficiency. A torque meter was used during these tests to measure directly the coupling power between the motor and the generator. That means a direct measurement of the generator losses.

In addition to the heat run tests the short-circuit ratio Kc was determined.

Dynamic characteristics were evaluated as well. Sudden short-circuit tests were performed to validate the calculated reactance’s and time constants.

The article also presents the factory validation tests of the new brushless exciter. It is designed and developed to take into consideration new improvements and power increases.

One of the main objectives of these factory tests is to validate compliance with thermal limits by measuring the temperature rise of the stator and rotor windings of the brushless exciter.