The Motor

The motor and controller for the E-Hawk have arrived. We decided on the Rotex Electric REX30 Motor and the HBC series controller from MGM Compro. The plan is to run the motor at either 86V (24s) or 100V (28s) depending on the battery we end up with. The motor is rated at 20kW max, and 8kW continuous. The motor is a 4-turn wind which yields a kV of 40 rpm/V. The controller is designed to work up to 120V and 280A continuous. The weight of motor and controller are 5.2 kg and 1.5 kg respectively.

In this installment of the blog we also design and build  a minimal electrical system consisting of a small battery pack, circuit breaker, some enable switches, and a potentiometer.  This allows us to power-up the system, learn how to configure the controller, and perform some preliminary tests.

The REX 30 motor has a diameter of 205 mm and a height of 46 mm.

The motor has 6 phase leads exiting the rear which are combined into 3 phase pairs at the controller. The cable bundle exiting in the top of the photo contains the hall sensor signal wires and temperature sensor signal wires.

The motor controller is relatively compact and according to the manufacturer is capable of pushing out 33kW continuously.

On the back side of the motor controller is visible the heat sink with cooling fans. The quality Rubycon input capacitors are encouraging.

The motor is finally mounted to the fuselage frame.

Aft view of the motor. The red disk is a 3D printed mock-up of the motor-to-propeller adapter plate. The prop we will be using requires the standard Rotax 6M8d75 hub bolt pattern. The plate will later be machined from aluminum.

The motor is fitted with a prototype prop for a fit check.

Side view of the installation.

This is the CAD model for a battery power combiner box. This will allow us to connect 4 6s Lipo batteries with XT90 connectors in series.

The combiner box is printed, XT90 connectors are inserted and wired in series.

The completed combiner box parts ready for assembly.

Voltage check of the 24s test battery pack.

The motor controller is temporarily attached to the fuselage frame. A wooden platform is also installed to support the balance of our test setup.

A 60A circuit breaker is wired in. It will allow us to quickly disconnect the traction pack if anything decides to go wrong.

The control panel from left to right: circuit breaker, precharge switch, auxiliary power (12V control electronics), and controller enable switch. The potentiometer knob is below the aux power switch. The Arduino will be used to read performance data from the controller and later display as flight instrumentation.