BLDC Motor Calculator
Compute RPM, electrical frequency, prop tip speed, and MCF8329A compatibility from battery, KV, and poles.
Inputs
Results
| Battery voltage (nominal) | 14.8 V |
| Battery voltage (full charge) | 16.8 V |
| Pole pairs | 7 |
| No-load RPM (KV × V_full) | 40,320 RPM |
| Loaded RPM (~85% of no-load) | 34,272 RPM |
| Electrical frequency | 4,704 Hz |
| Electrical frequency | 4.70 kHz |
| PWM cycles per electrical cycle (at 48 kHz) | 10.2 |
| Prop tip speed | 228 m/s |
| Mach number | 0.66 Mach |
MCF8329A: Exceeds limit ✗
Electrical frequency 4,704 Hz exceeds the 1,800 Hz observer limit. Your motor needs 2.6× the MCF8329A's capability. Max KV for 14 poles at 16.8V: 918 KV (your motor is 2,400 KV). Use a discrete MCU + gate driver (e.g. FD6288Q + AT32F421 + AM32 firmware).
Formulas used:
f_electrical = (RPM × pole_pairs) / 60No-load RPM = KV × V_battery (full charge = S × 4.2V)
Loaded RPM = No-load RPM × 0.85 (typical 5" prop load factor)
Tip speed = RPM × π × D(m) / 60
MCF8329A limit: 1,800 Hz electrical frequency
KV_max for MCF8329A = (1,800 × 60) / (pole_pairs × V_battery)