3 MW-Class Steam Turbine Power Conversion Solution

INOMAX can evaluate an alternative converter package for an existing turbine-generator system. The replacement review covers generator type, speed and voltage envelope, continuous current, grid-side functions, control ownership and fault protection. Provide the original converter specifications, generator data and plant diagrams. Existing equipment can be retained where compatible, but matching a brand’s headline kW rating does not establish an interchangeable converter or control system.

Yes, a project-specific selection can be evaluated for another high-speed PM generator. Required data include pole count, rated and maximum speed, electrical frequency, current, back-EMF curve, inductance, insulation limits and feedback requirements. A generator with the same power can impose very different voltage and switching requirements. The 8,000 rpm machine in this proposal provides a design example, not a universal speed or frequency limit.

INOMAX can review different power levels using an application-specific converter and module arrangement. Continuous electrical output, generator current, overload duty, voltage, cooling and grid-side capacity determine the selection. Installed module capacity must not be treated as guaranteed plant output. This reference uses a 3 MW-nameplate generator with a separately defined generating duty of up to 2.5 MW; a different duty requires a new electrical and thermal check.

Different grid voltages and frequencies can be assessed during system design. Generator-side voltage and grid-side voltage must be considered separately, together with converter ratings, DC-link limits, filters, protection and any transformer. This proposal specifies 690 V, 50 Hz. A 400 V or 60 Hz requirement should be included at enquiry stage so the grid interface is engineered for that network rather than assumed compatible with the reference design.

It is relevant to projects that need controlled conversion between a variable-frequency generator and an electrical supply, including suitable steam-based waste-heat recovery and combined heat and power (CHP) applications. Feasibility depends on the generator, turbine operating range, required controls and grid connection. Other prime movers or generator technologies require their own review. This case demonstrates an engineering approach; it does not establish a completed installation in every adjacent application.

A three-level topology is worth evaluating when machine voltage, switching stress, harmonics or a high-speed generator’s insulation requirements make waveform quality especially important. The choice must consider motor-side dv/dt, electrical frequency, cooling, filters and total system complexity. INOMAX selected three-level conversion for this PM-generator proposal. Another machine may need a different topology; the selection should follow generator and grid requirements rather than power rating alone.

Grid-connected, islanded and black-start operation require different control and protection functions. This engineering case addresses grid-connected generation and should not be treated as proof of grid-forming or black-start capability. If island operation is required, specify how voltage and frequency will be established, how loads are shared, the available starting energy and the transfer sequence. INOMAX can review the additional scope with the turbine and plant-control suppliers.

The protection concept must address continuing turbine input, rotor energy, generator back EMF and the loss of a grid export path. In the proposed approach, steam-valve closure, controlled deceleration and a braking branch are coordinated, with UPS-backed controls for the intended stop sequence. Braking energy and thermal duty need calculation; a peak braking-module rating alone does not establish stopping capability. Independent turbine protection and mechanical overspeed protection remain part of the overall system design.

The existing cooling system can be assessed against converter heat loss, coolant quality, temperature, flow, pressure and materials compatibility. A liquid-cooled arrangement is used in this proposal. If air cooling is preferred, the power-module selection, ventilation demand, ambient conditions and cabinet space must be reviewed as a different design. Cooling-unit supply and the boundary between internal and plant-side circuits should be stated explicitly in the quotation.

The control architecture can be developed around agreed speed, power and torque commands, status feedback, trips and interlocks. Define which controller owns each operating mode and how the system behaves after a communication failure. The platform proposal describes PROFINET, EtherCAT, EtherNet/IP, Modbus TCP and CANopen options; the selected hardware and protocol must be confirmed for the actual project. Interface mapping and acceptance tests belong in the engineering scope.

Compliance must be defined against the installation country, utility requirements and selected equipment. Request the applicable product certificates and test reports, and agree the site-specific harmonic, protection, EMC and grid-connection requirements before ordering. An AFE or low-harmonic topology alone does not establish utility approval. The proposal should allocate responsibility for network studies, protection settings, required tests and final acceptance, rather than assume that a reference design is pre-approved for every grid.

Provide the generator data and back-EMF curve, turbine operating and trip requirements, grid information, load profile, cooling conditions, control interfaces and target schedule. Compare converters on continuous duty, fault-energy handling, filters, cabinet and cooling scope, engineering documentation, FAT, commissioning responsibilities, spare parts and warranty. INOMAX can discuss a defined converter package within the wider turbine project; turbine, generator, civil works and site services should each have an explicit scope owner.