Some of you may have wondered, why does the Inokim Light motor produce a humming sound? And why does a similarly powered 350W I-MAX Q5 motor run so quietly?
Both the Inokim Light and I-MAX Q5 motor are both 350W powered BLDC (brushless DC) hub motors. However, why do they perform so differently? The Inokim Light motor is smooth and accelerates quickly but produces a humming sound, whereas the I-MAX Q5 motor is similarly smooth but produces a more gradual acceleration with almost no noise.
A simple explanation for our readers is that the Inokim Light uses a square wave speed controller (or more commonly known as ESC) whereas the I-MAX uses a more efficient sine wave controller.
An Inokim Light square wave speed controller (pic above) is able to transition to max power faster with its step power curve. The controller is also able to maintain a high level of power output for a longer period of time. Thats the upside. The downside is that it produces more noise hence less efficient due to harmonic losses.
This is how a speed controller looks like for e-bikes and e-scooters. The waveform whether sine or square wave function, is programmed inside this silver box.
An I-MAX Q5 controller’s sine-wave power curve experiences slower power output increase with its gradual curve. However, it is more efficient with power as it does not require a quick burst of current from the battery to ramp up its power. Overall, it has a slower ramp-up to top speed but a more efficient and quieter ride.
A good analogy for the difference between square wave and sine wave is like pushing a bowling ball down the street. Sine wave uses a smooth constant push the whole way, while square wave attempts to simulate the same forces but uses constant jabbing/nudging.
Finally, to fully comprehend, watch this video of how the SAME motor powered by both types of waveform performs:
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