Supported Electric Motor Types
NavCad supports the following electric motor drive types:
- DC motors including constant torque (PMSM-style) and constant torque-constant power types. NavCad provides generic builders for both styles.
- AC three-phase induction motors NEMA A/B induction type with estimated partial load motor efficiency and power factor.
- AC permanent magnet motors PMAC type with updated partial load efficiency model (NavCad 2024).
Electric Motor Data Entry
Electric motor data is entered through dedicated Motor Object Data forms (DC Motor Object Data or AC Motor Object Data) accessed through the Drive Data page. Unlike IC engine data entry which uses RPM–brake power curves, electric motor entry uses the motor-specific parameters:
- Motor type: select generic or custom.
- Voltage (input voltage).
- Rated torque or power at rated RPM.
- No-load RPM (the maximum operational RPM where torque and power decline to zero).
- Parasitic load (power consumed by non-propulsion demands drawing from the motor).
For custom motor curves, the full RPM–torque relationship can be entered directly from manufacturer data.
Electric-Specific Outputs
In addition to standard propulsion results (shaft power, propeller thrust, speed), NavCad adds electric-specific outputs when an electric drive is defined:
- Electrical input power (kW or kVA).
- Current draw at each operating speed.
- Motor mechanical-to-electrical efficiency.
These values feed directly into battery sizing, range estimation, and electrical system design.
Propeller Sizing for Electric Drives
Electric motors have different torque and power curve shapes from IC engines a constant-torque motor delivers from zero , which changes the optimal propeller design point. NavCad 2025 improved the design point estimation for propeller sizing with electric motor drives to account for these differences and use the unique characteristics of electric motors to advantage.
Note on Retrofit Analysis
NavCad's electric drive support is well suited to analyzing IC-to-electric retrofit scenarios the resistance curve from the original hull data can be retained while the drive system is changed to an electric configuration, allowing direct comparison of performance and electrical demand before committing to a retrofit.
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