# potentiometer for DC and AC Motors



## cfckevmccfc (Mar 10, 2010)

how do you choose a poteniometer for DC and AC motors? what factors do you need to consider? and where would you find suitable ones for EVs?


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## dtbaker (Jan 5, 2008)

cfckevmccfc said:


> how do you choose a poteniometer for DC and AC motors? what factors do you need to consider? and where would you find suitable ones for EVs?


a 'pot box' is basically like a dimmer switch.... a variable resistor attached to a foot or hand throttle that tells the motor controller how much juice to send to the motor. Curtis pb-6 is a popular choice, but there are others....

typical range is 0-5kOhm compatible with popular controllers available from anywhere that sells EV motors and controllers like evComponents.com, kta-ev.com, and many others....


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## cfckevmccfc (Mar 10, 2010)

dtbaker said:


> a 'pot box' is basically like a dimmer switch.... a variable resistor attached to a foot or hand throttle that tells the motor controller how much juice to send to the motor. Curtis pb-6 is a popular choice, but there are others....
> 
> typical range is 0-5kOhm compatible with popular controllers available from anywhere that sells EV motors and controllers like evComponents.com, kta-ev.com, and many others....


So if i am using a 72V 335A DC Motor then will the Curtis PB-6 be able to support this ok ? how do set each gear speed ?


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## dtbaker (Jan 5, 2008)

cfckevmccfc said:


> So if i am using a 72V 335A DC Motor then will the Curtis PB-6 be able to support this ok ? how do set each gear speed ?


the pot-box needs to be compatible with the CONTROLLER, not really the motor. Many Controllers use 0-5k Ohm as throttle input signal, but you need to check.

The 'gear speed', I don't know what you mean.....?


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## cfckevmccfc (Mar 10, 2010)

dtbaker said:


> the pot-box needs to be compatible with the CONTROLLER, not really the motor. Many Controllers use 0-5k Ohm as throttle input signal, but you need to check.
> 
> The 'gear speed', I don't know what you mean.....?


the controller is Alltrax 7245 72V, 450A. by gear speed i mean like if how does the potentiometer know what power to be delivered to each gear as in 1st 2nd 3rd......


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## dtbaker (Jan 5, 2008)

cfckevmccfc said:


> the controller is Alltrax 7245 72V, 450A. by gear speed i mean like if how does the potentiometer know what power to be delivered to each gear as in 1st 2nd 3rd......


the pot box does not know or care what gear you are in.... only how far you have depressed (or twisted) the accelerator. The variable resistance of the pot-box lever position tells the controller how many amps to try to deliver from 0-100% regardless of what gear you are in.


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## cfckevmccfc (Mar 10, 2010)

dtbaker said:


> the pot box does not know or care what gear you are in.... only how far you have depressed (or twisted) the accelerator. The variable resistance of the pot-box lever position tells the controller how many amps to try to deliver from 0-100% regardless of what gear you are in.


 
so how is the gears selected .. what device do u use ?


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## TheSGC (Nov 15, 2007)

cfckevmccfc said:


> so how is the gears selected .. what device do u use ?


Your car's existing transmission is used to change gears. 

A motor controller used a Potentiometer to take user input and send out the power to the motor using Pulse Width Modulation to create a Duty Cycle that varies the speed and torque of the motor depending on how far the pedal is pressed.


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## Roy Von Rogers (Mar 21, 2009)

I believe he's thinking about an automatic transmission.

CFCK there is a discussion in here about automatics. Most of the conversions use a stick shift tranny, and it has nothing to do with the accelerator potbox, you just use whatever gear matches the motor curve and your need for speed or acceleration.

Roy


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## dtbaker (Jan 5, 2008)

cfckevmccfc said:


> so how is the gears selected .. what device do u use ?


the simplest is the manual transmission gear shift. 

Retaining an 'Automatic' transmission is POSSIBLE, but takes a lot of extra fooling around to send speed and set shift points electronically as well as requiring a pump for the transmission fluid pressure.


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## cfckevmccfc (Mar 10, 2010)

ok i got that problem solved .. iv got a new one nw .. i have a VFD for my AC motor .. do i need a pot box to talk to my VFD and how do i choose a compatable one ?


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## TheSGC (Nov 15, 2007)

cfckevmccfc said:


> ok i got that problem solved .. iv got a new one nw .. i have a VFD for my AC motor .. do i need a pot box to talk to my VFD and how do i choose a compatable one ?


That is where things can get complicated. Do have a model number of the VFD? I don't know of any VFD's that even have an option for a pot box, they are usually digitally controlled using the interface, so it could be somewhat of a challenge.


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## cfckevmccfc (Mar 10, 2010)

The VFD I have chosen is the DURApulse GS3-4100 rated at 460V, 160A and 100hp max output. When u say digitally controlled what do you mean? .. my knowledge is very limited on electric vehicles am just a student . with this VFD connected would i need a potentiometer installed if not what other method should be used ?


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