The EcoSpeed EMtnD and EMD units use high speed brushless DC motors. High speed motors produce more power per unit weight than lower speed motors such as are used in hub drive systems. Brushless means that there are no mechanical switches inside the motor to wear out, so maintenance is eliminated and reliability is much higher.
1300 Watt Motor
We rate our standard motors at 1300 Watts.. Notice the “we rate” statement. It’s a common misconception that electric motors just produce a fixed amount of power based on some property of the motor, such as its size. Actually, electric motors are just like gas engines in that they can be, in effect, tuned to produce different amounts of power. We won’t go into all the fine details, but the power a motor can supply is mostly set by the controller. So we set our Velociraptor controller to 2 settings, one at 750 Watts (economy mode) and one at 1300 Watts our off-road max power limit.
Electric Motor Basics
Electric motors operate on the principal of using the magnetic field that surrounds any wire carrying electrical current to attract either another current carrying wire or a permanent magnet. In the latter case, it is referred to as a permanent magnet (PM) motor. If it then uses direct current (DC) as its source of power, it is a PM DC motor.
In a motor, the current carrying wire is wound tightly around a metal frame to concentrate the strength of the magnetic field and so is called a “winding”. Of course, if two magnets, or a winding and a magnet, are attracting each other, they will move as close together as they can and then stop. To get the continuous motion that characterizes a motor more than one winding is needed. The current is then switched off when a magnet moves close to a winding and at the same time the current in another winding further away is switched on thus continuing the motion. This switching process is called commutation.
If the commutation is done mechanically, by switches (brushes) activated by the rotating motor, it is a brush PM DC motor. If the commutation is done electronically via motor shaft position sensing and power transistors, then it is a brushless PM DC motor, usually shortened to just brushless DC motor. The brushless DC motor is the more expensive design but has the advantage of not having mechanical brushes that wear out and need periodic replacement.
All motors used for transportation need some means of varying speed and power output under user control, analogous to the carburetor or fuel injection on a gasoline engine. This function is provided by the motor speed controller. For a brushless motor, the speed controller and the commutation electronics are integrated and the whole assembly is simply called the controller. For a brush motor, the controller is simpler because the commutation is mechanical. The controller takes commands from an input device that gives a it signal, in the form of a voltage, telling it how fast to spin or, in more sophisticated designs like or Velociraptor, how much power to put out. That device, mounted on the handlebar of an electric bike is called, appropriately enough, the “throttle”.
The controller varies motor power using a technique called “pulse width modulation” (PWM), which is just an engineer’s way of saying that it turns the current on and off really fast, but leaves it on longer when more power is needed. Listen carefully to a running motor and you can hear the change in pitch as the PWM “duty cycle” is varied by the controller.