Field-Oriented Control (FOC) is the technology behind every smooth-driving EV. It's why your car accelerates without jerking, why regen braking feels natural, and why the motor stays quiet at all speeds. All CMVTE motor controllers use FOC. Here's how it works and why it matters for your conversion.
What FOC Does
FOC (also called vector control) separates the motor current into two parts: torque-producing current (quadrature / Q-axis) and magnetic-field current (direct / D-axis). By controlling these independently, the controller can deliver maximum torque from 0 RPM, maintain efficiency at any speed, and switch seamlessly between drive and regen. Without FOC, a PMSM motor would cog at low speed, whine at high speed, and waste energy.
CMVTE FOC Controller Lineup
| Model | Motor Match | Input Voltage | Peak Current | Max Power | Regen | CAN Bus | Cooling | Price |
|---|---|---|---|---|---|---|---|---|
| FOC-350A | PMSM-15, PMSM-25 | 96-144V | 350A | 45 kW peak | Yes | Yes | Fan | $1,200-$1,800 |
| FOC-500A | PMSM-35, PMSM-50 | 96-384V | 500A | 80 kW peak | Yes | Yes | Water | $2,000-$3,000 |
| FOC-800A | PMSM-50, PMSM-80 | 144-450V | 800A | 120 kW peak | Yes | Yes | Water | $3,500-$5,000 |
FOC vs Six-Step Commutation
| Six-Step (Basic BLDC) | FOC (CMVTE Controllers) | |
|---|---|---|
| Torque ripple | ~3-5% (cogging at low speed) | <1% (smooth at all speeds) |
| Low-speed control | Jerky, needs high gear reduction | Full torque, smooth from 0 RPM |
| High-speed efficiency | Drops above rated RPM | Maintains 90%+ across RPM range |
| Regen braking | Not supported natively | Built in, adjustable |
| Noise | Audible commutation whine | Silent |
How FOC Works (Simple Version)
- Measure current: The controller samples motor current 10,000+ times per second using high-speed ADCs
- Transform to D-Q frame: Clarke and Park transforms convert the three-phase currents into two values — D (magnetic field) and Q (torque)
- Control independently: The PI loops keep Q at the target torque and D at zero (no wasted field energy)
- Transform back: Inverse transforms convert the corrected D-Q values back to three-phase voltage commands for the inverter
- Apply voltage: Space Vector Modulation (SVM) generates the exact three-phase sine waves to drive the motor
The whole loop runs every 50-100 microseconds. The result is instant torque response with no lag, no cogging, and no whine.
What FOC Means for Your EV Build
- Smooth starts: No clutch judder — the car creeps forward like a factory EV
- Full torque at 0 RPM: Instant acceleration without revving
- Regen braking: One-pedal driving, adjustable regen strength, 10-20% energy recovery
- Wider speed range: FOC + field weakening lets the motor run efficiently from 500 RPM to 7,000+ RPM
- Quiet operation: No high-frequency whine at any speed
Every CMVTE controller is programmed with motor-specific FOC parameters for the PMSM model it ships with. This means the controller arrives with the correct current limits, angle offset, and PI gains pre-loaded. Plug in the motor, connect the battery, and the system runs. No manual tuning required. If you swap motors or change battery voltage, the CAN bus interface lets you update the parameters in minutes.
For sensorless builds, CMVTE FOC controllers use a back-EMF observer to estimate rotor position at any speed. This means no encoder or Hall sensors to install — just the three motor phase wires. Startup is reliable even under load because the controller injects a high-frequency signal at standstill to detect the initial rotor position before applying torque.
Browse CMVTE FOC controllers →
Get a Controller Recommendation
Tell us your motor model, battery voltage, and target power. We'll match you to the FOC controller with the right current rating, cooling type, and CAN bus configuration — plus a wiring diagram and tuning file.
WhatsApp / Phone: +86 181 2358 8272
Email: [email protected]
Mention "FOC" for a controller recommendation specific to your motor and battery.
