Case Study: Powering a Four-Kraken Swerve Drive

Swerve is the most power-hungry common FRC drivetrain: eight motors (four drive, four steer) plus encoders and a gyro, all on CAN. Here is a real, worked electrical configuration using current-generation hardware.

Hardware: 4x Kraken X60 (drive) + 4x Kraken X60 or X44 (steer), each driven by its integrated Talon FX; 4x CTRE CANcoder for absolute azimuth position; 1x Pigeon 2.0 IMU for heading. Power each Kraken from its own 40A MX5-A breaker in the PD over 12 AWG (R622: 31-40A circuits require 12 AWG).

Why this browns out if you do nothing: a single Kraken X60 stalls at about 366A at 12V (and about 483A with FOC), so four drive Krakens can momentarily demand well over a thousand amps on a hard direction change, which collapses battery voltage straight through the 6.3V/6.75V brownout floor in well under a second.

The current-limit configuration (Phoenix 6, per drive motor):

var limits = new CurrentLimitsConfigs();
limits.StatorCurrentLimit = 120;       // wheel-slip / heat control
limits.StatorCurrentLimitEnable = true;
limits.SupplyCurrentLimit = 70;        // brownout / breaker protection
limits.SupplyCurrentLimitEnable = true;
limits.SupplyCurrentLowerLimit = 60;   // sustained clamp
limits.SupplyCurrentLowerTime = 1.0;
driveTalon.getConfigurator().apply(limits);

Steer (azimuth) motors rarely need peak torque, so a lower stator limit (~60A) is plenty and reduces heat. The 120A stator / 70A supply pairing is a widely used community starting point for swerve; CTRE recommends tuning these empirically for your specific robot rather than treating any pair as a fixed rule.

Brownout math: four drive motors at 70A supply = 280A worst case, but because the supply limiter clamps each and the wheels are usually not all at peak simultaneously, real sustained draw lands well under that and inside a ~180A planning budget. Confirm by logging getSupplyCurrent() across all four and graphing total current vs. battery voltage.

Sensors on the bus: CANcoders and the Pigeon 2 add CAN traffic. With 8 motor controllers + 4 CANcoders + 1 Pigeon + the PD, the roboRIO's standard CAN bus utilization climbs fast. This is the classic trigger to move the drivetrain onto a CANivore CAN FD bus (next lesson).

Wiring discipline that matters here: daisy-chain CAN cleanly through each module, twist CANH/CANL, secure every connector against the constant vibration and impacts swerve modules see, and route motor power away from CAN to reduce noise. Label every CAN ID, because eight nearly-identical Talon FX devices are easy to confuse.

Done right, this drivetrain accelerates aggressively, holds heading via the Pigeon 2, and never browns out, on a fresh battery in qualifications and on a tired one in finals.