For high-voltage wound-rotor (slip-ring) motors, rotor voltage does change with rated power—but not in direct proportion. It is a design parameter determined by power, speed, stator voltage, and winding configuration.
Key Relationships
- Larger electric motors(higher kW) → higher rotor voltage (typically). To limit rotor current and reduce brush/slip-ring losses, manufacturers design higher rotor voltages for large-frame motors (e.g., 1000–5000 kW).
- Rotor voltage is not standardized. Two motors with identical kW can have different rotor voltages based on speed (poles) and stator voltage (6 kV / 10 kV).
- Example: A 630 kW 6 kV motor may have ~860 V rotor voltage; a 2500 kW 10 kV motor often exceeds 1500 V.
Why It Matters for Quotations
- Starting equipment (liquid resistance) must match rotor voltage.
- Spare brushes/slip-rings depend on voltage and current ratings.
- Always verify rotor voltage on the motor nameplate or technical datasheet—never assume based solely on kW.
In short: rotor voltage rises with rated power but is a custom design value, not a fixed ratio. Always confirm full parameters for accurate quoting and system compatibility.