T-MOTOR ALPHA 120A 12S

The T-MOTOR ALPHA 120A 12S is a single-motor ESC from the Chinese maker T-MOTOR for the large U-series motors in heavy multicopters. It uses proprietary FOC firmware (field-oriented control), drives one motor and weighs 359.5 g including leads.

Despite the 120 in the name the continuous current is 100 A; the 120 A is the peak current for 10 s. Sizing follows the 100 A. The voltage window runs from 6S to 12S, i.e. up to 50.4 V fully charged. Control is by PWM. FOC runs sinusoidally, more quietly and more efficiently than block commutation, but regulates more slowly, which hardly matters with large, sluggish propellers. The controller brakes actively: when the flight controller takes throttle away, the motor is braked electrically and its speed falls faster; voltage spikes can arise at the battery input.

Frame and law: U-series motors drive large propellers, and the builds are often at or above 25 kg take-off mass; from there the specific category with an operational authorisation applies. On 12S an ampere-hour of battery is 44.4 Wh, and from about 3.6 Ah a pack passes the IATA limit of 160 Wh.

For selection: motor and controller are matched as a pair, and the motor's continuous current plus reserve stays below 100 A. The 359.5 g includes the leads; the board alone weighs less. As for wear, voltage spikes during braking load the capacitors at the input; check the solder joints of the power connections and the lead insulation after vibration and heat.