Shanghai Dualsky Models Co., Ltd. XM5050EA-29SE V3 250KV

The Dualsky XM5050EA-29SE V3 250KV is an outrunner from the EA V3 series for mid-size multicopters. Dualsky is a manufacturer from Shanghai; this version is meant as a 12S high-voltage motor for unmanned aircraft (UAV). The case measures 49.5 mm in diameter and 48.2 mm in height, and the motor has 12 slots and 14 poles (12N14P) and a 6 mm shaft.

At 250 KV the motor turns slowly and delivers high torque, which suits large propellers: the maker names 15x8E and 15x10E for 12S. On 12S at 44.4 V nominal that works out at roughly 11,100 rpm unloaded. The motor weighs 290 g and reaches up to 1,776 W at up to 40 A. The two figures agree: 40 A at 44.4 V gives exactly 1,776 W. They are peak values, not continuous ones. Permitted cell counts are 10 to 12S.

On 10 to 12S the drive runs at voltages above 50 V (a fully charged 12S pack is 50.4 V). Speed controller (ESC) and battery must be rated for that voltage, and the controller needs headroom above the 40 A. Power and current figures refer, depending on the maker, to time spans between 3 and 180 s and can only be compared on the same time basis. The whole aircraft counts for the rules too: a quadcopter with four of these motors carries 1,160 g of motor mass alone, which is already above the 900 g of class C1.

With 15-inch propellers the bearings work under constant load from thrust and imbalance; an out-of-round or poorly balanced propeller shortens their life. In high-voltage operation the battery connectors should have spark protection, because plugging in sends charging current into the controller capacitors. Winding insulation ages under sustained heat; a motor that runs hot in a hover is working with a propeller that is too large or a load that is too high. Magnets can lose strength through overheating.