# Function of EV controller?



## major (Apr 4, 2008)

dvnccbmacbt said:


> Hi all,
> 
> I have a question about the function of EV controller, in general. Do the EV controllers have speed regulator function or not? I mean with the same pedal position, do the EV controller maintain the same speed no matter the load (slope street, wind resistance force ... )?
> 
> ...


Hi dvnc,

Why do you ask?

I assume you speak of the motor controller in the EV. With AC drives it uses the throttle input signal from the driver to command torque from the motor. So pedal position determines the torque output of the motor or in turn the driving force propelling the vehicle. So if the forces resisting motion like the wind or road incline increase, the vehicle will slow with a constant pedal position. To maintain a set speed when encountering an incline you press further on the pedal just like a normal gas car.

With DC drives, the motor controller uses the command input to set a voltage to the motor which determines the RPM but is load dependent, so will slow as load is increased with a constant pedal position.

The electric motor may have a speed sensor and that signal is used in various ways depending on the type of motor and controller. On AC motors it is needed for the commutation or torque producing algorithm. On DC motors it is used for overspeed protection.

Of course on EVs you can use cruise control like you find on gas cars and such cruise controls do hold vehicle speed constant according to the set point.

Hope that helps,

major


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## dvnccbmacbt (Feb 28, 2014)

Thank you very much! I understanded this problem!


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## major (Apr 4, 2008)

dvnccbmacbt said:


> Thank you very much! I understanded this problem!


What problem


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## Qer (May 7, 2008)

major said:


> With DC drives, the motor controller uses the command input to set a voltage


Nope, that would result in a very uncomfortable ride. If you're not a total klutz you make the software control the current...

Ponder it; Let's say we have a Shiva with 400 Volt in, press the throttle down 10% so it applies 40 Volt into a motor that's stopped. Can we say gut-ripping takeoff?


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## major (Apr 4, 2008)

Qer said:


> Nope, that would result in a very uncomfortable ride. If you're not a total klutz you make the software control the current...
> 
> Ponder it; Let's say we have a Shiva with 400 Volt in, press the throttle down 10% so it applies 40 Volt into a motor that's stopped. Can we say gut-ripping takeoff?


The current voltage relationship is a one to one function. How do you control the current? By the voltage through the duty cycle, right? 

I was keeping my reply simple  What do you suppose the problem is? And why won't dvnccbmacbt answer my questions 


dvnccbmacbt said:


> I understanded this problem!


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## Qer (May 7, 2008)

major said:


> The current voltage relationship is a one to one function.


With an offset depending on RPM, yes...


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