Permanent-Magnet Generator Inquiry: Prime-Mover and Output Data

A permanent-magnet generator converts mechanical input into electrical output. Treat it as a separate inquiry from a motor: the prime mover, load, output electronics, and overspeed conditions define the project.

Describe the prime mover

Identify whether the source is a water turbine, wind turbine, engine, expander, or test system. Provide the available torque and speed curve if known, expected operating range, rated point, starts and stops, and the maximum speed that could occur during a load rejection or fault.

Do not assume that a motor’s rated speed or torque is a valid generator operating point. The generator and prime mover must be assessed together.

Define the electrical output

Specify whether the required output is AC or DC, voltage, phase count, frequency or DC-bus range, load type, power factor if relevant, rectifier or inverter, grid connection, and protection requirements.

For a synchronous generator, electrical frequency is related to mechanical speed and pole-pair count:

Here, p is pole pairs. This relationship is useful for checking a requested frequency against a stated speed. It does not establish the winding, voltage, thermal rating, or output capability of a particular machine.

Mechanical shaft power and torque at a stated speed are related by:

Use consistent units and distinguish mechanical input power from electrical output. Losses, load behavior, voltage regulation, temperature, and operating limits require design-specific data.

Include overspeed and protection conditions

State the normal maximum speed and credible overspeed condition. Ask how open-circuit voltage, rectifier or inverter limits, dump loads, braking, and disconnection will be handled. Agree who supplies each protection device and who verifies the complete system.

Request evidence only against an agreed test condition. A voltage-versus-speed curve should identify the winding connection, measurement points, load state, temperature, and instrumentation. Do not infer runaway limits from an illustrative curve.

Generator RFQ checklist

• Prime-mover type, torque-speed curve, rated point, and maximum speed.
• Electrical output, load, power electronics, grid or DC interface.
• Shaft orientation, mounting, bearings, and allowable mechanical loads.
• Cooling, environment, enclosure, and operating duty.
• Overspeed, open-circuit voltage, braking, and protection requirements.
• Required test records, acceptance limits, quantity, and destination.

Generator model, output rating, voltage regulation, protection, supplier identity, documentation, and delivery terms must be confirmed for the project before quotation.