Electrical – IM or BLDC for a go kart

induction motormotor

I read that the surge current for an Indction motor is higher than that of other motors. Therefore when one wants to power a 3phase IM the inverter rating should be much higher than that of a BLDC (when the supply is DC ). Is it true?

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Link to this: http://www.diygokarts.com/vb/showthread.php?t=9700

I am gonna start designing an electric go kart(for an event). I wanted to use an induction motor because of the following reasons:

  • Better overall or avg efficiency.

  • lower weight

This is from where I was like convinced to use an IM against BLDC: https://www.tesla.com/blog/induction-versus-dc-brushless-motors?_ga=2.70427863.694368311.1506343498-425824400.1494234243

Specs of the motor and batteries that I'm allowed to use [some extra info if it's needed ]:
– Motor rating <= 3kW
– Battery voltage = 48 V
– 20 Ah <= Battery capacity <= 50 Ah
– Max rpm = 3600
– Max torque = 10 Nm

Any advice is welcome.

Best Answer

Is it true?

Absolutely not. The quoted statement is totally nonsense.

However there is definitely a right way and a wrong way to use an induction motor. You must have an inverter that is specifically designed to control an induction motor. More specifically, you need a variable frequency drive (VFD). A VFD will start the motor at a low frequency and proportionally low voltage. To accelerate the motor, the frequency are increased together. If that is done properly, the motor can produce 150% of its rated torque at any speed up to the rated speed.

A sensorless vector VFD can get more out of the motor, more consistently and have an easier set-up procedure. Don't use a VFD designed to drive fans and centrifugal pumps, that is, use a constant-torque rated VFD not a variable-torque model. If a product line lists "standard-duty" and "heavy-duty" models, use the heavy-duty one.

Be aware that you can not get the performance of a Tesla, not even a "scaled down" version of that performance. Both the Tesla motor and the Tesla VFD are very special designs that "are not sold in stores."

Note that a Tesla uses a high battery voltage. You will probably not find an adequate motor and VFD that require a battery voltage less than about 300 volts.

Neither an induction motor nor a BLDC motor are really good choices for the first effort of this sort by someone without experience with those technologies. A DC motor with a commutator will be best in that case.

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