Re: Electric vehicles - Types of motors? Quote:
Originally Posted by Samurai Since we are talking about DC motors for EVs, how can we depend on load to control the speed? What if the driver wants to go faster? Reducing load is not answer.
Since BLDC motors work on the principle of magnetic push and pull force, I thought varying the voltage will let us select the speed under a give load, using closed loop control circuit. So I am not able to follow your logic. |
My earlier post was about PMSM motor and not EV motors.
Now for EV motors:
From what i understand, EV motors are of two types either DC stepper motors or AC induction motors. The article which Jeroen refered to, mentions that newer tesla models uses a switched reluctance motor. A switched reluctance motor is essentially a DC stepper motor. Steppers are controlled by pulsing from a controller which is attached to a power supply (battery). A stepper takes a fixed number of pulses per rotation. Say in full step mode , it would be around 360 pulses ( 5V DC ).
When pressing the pedal, we either increase or decrease the pulses thereby varying the speed. However, what is important is that even here, the current that the stepper draws from the controller would depend on the mechanical load. The controller has a inbuilt power management circuit. Simple DC circuitry logic is that both the terminal voltages of the controller and motor would be same and current drawn depends on load.
The older TESLA motor was a 3 phase AC induction motor. For such a motor, to run it from a battery ( DC) , you first convert DC to AC using a SCR firing circuit and then use a bridge circuit to vary the frequency. So in effect you control the frequency and the motor again would take a current depending on load.
Last edited by srini1785 : 10th September 2019 at 14:07.
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