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Old 03-10-2016, 12:33 AM   #11
Brianflys
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Default Re: Alltrax controller questions

What do these high performance controllers do to the cart range? Is it a linear relationship of higher speed to lower range? I have a G29 with new 6x8 batteries and like the idea of better than 19 mph. But not if range suffers. Just getting the new batteries broken in and like the extra range particularly since it includes driving on the Texas beach.

What do I lose with the Alltrax controller (assume the 400 amp model)?

Last edited by Brianflys; 03-10-2016 at 12:33 AM.. Reason: fat fingers...
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Old 03-10-2016, 09:06 AM   #12
Volt_Ampere
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Default Re: Alltrax controller questions

More performance = less range. (If you constantly use it)
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Old 03-10-2016, 09:43 AM   #13
scottyb
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Default Re: Alltrax controller questions

The ability to allow the motor to draw more amperage (bigger control) does not make the motor draw more amperage, your right foot does.

I hope this helps
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Old 03-10-2016, 10:20 AM   #14
Sergio
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Default Re: Alltrax controller questions

While that statement is correct, unless You just wasted money buying a controller that You did not need, You will certainly use more energy from the pack.

The after market controllers have a different 'Field Map' for the motor, even at lower speeds, they increase the Field current, which increases the Field Flux and forces the Armature to use more current and therefore create more torque.

The additional "Torque" most likely puts the motor further away from its 'Efficiency' curve, so You will also waste more energy as heat in the motor.

Reducing the "Throttle Rate" will save some energy as it will allow the motor to more gradually increase its speed while remaining closer to its "efficiency curve".

I agree with volt_ampere on this one, if You are experiencing better performance, You are using more energy and will have a reduced range.
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Old 03-10-2016, 10:57 AM   #15
scottyb
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Default Re: Alltrax controller questions

The response about field maps applies to sepex drive systems only.
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Old 03-10-2016, 12:53 PM   #16
Volt_Ampere
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Default Re: Alltrax controller questions

And this statement is incorrect. More field current generates more torque with the same armature current. BEMF is proportional to RPM * Field Flux so Armature current drops when Field current increases unless the controller generates a higher armature voltage.
A good field map will make the sepex motor run more efficiently.
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Old 03-10-2016, 02:05 PM   #17
Sergio
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Default Re: Alltrax controller questions

You are missing the point, For You to maintain the same speed with a higher Field current, the Armature current will have to increase.

Or are you somehow suggesting that if I increase the Field Current the motor will continue to run at the same RPM but with more torque and using less Armature Current?

The question was about a G29, which I looked up before answering and it was a Sepex motor.

I stand by the quote below regardless if it is a Sepex or Series System:

If the only change You made to the cart was add a new Controller:

Quote:
if You are experiencing better performance, You are using more energy and will have a reduced range
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Old 03-10-2016, 02:31 PM   #18
Volt_Ampere
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Default Re: Alltrax controller questions

Not correct! Same speed if possible with the fixed amount of voltage available will be at lower current if you increase Field current! Torque is proportional to Current and Field Flux. To maintain same speed you need same torque which means if field flux (current) goes up, the armature current goes down. This is the advantage of a field map on a sepex motor.
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Old 03-10-2016, 06:47 PM   #19
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Default Re: Alltrax controller questions

I am sure if we were on a Lab we could manually dial the most efficient parameters for each combination of Speed and Load.

But since this is a practical application question, the relationship between Field current and Armature current on Controllers like the Alltrax is fixed and established by the Motor Field Map loaded.

If the Map was the same as the OEM, the performance would be the same as well.

It would seem reasonable that the Alltrax curve has a higher Field Current limit to allow the motor to develop more torque and it requires additional overall current for that.

If You look at a Controller like the Curtis 1268 where You can define Your own "Field Map", this is how they describe the "Maximum Field Parameter":

Quote:
FIELD MAX
The maximum field current limit parameter defines the maximum allowed
current in the motor’s field winding. Its setting will determine the motor’s
maximum torque during drive operation, and will limit the power dissipation
in the field winding itself.
So the Field Current directly affects the amount of Torque the Motor is allowed to develop.

I remembered an exchange I had with SilverWolf about the MadJax Torque controller, that could be a good option where You could adjust it for maximum range (while sacrificing the Torque when it was not needed).

Quote:
The advantage or our Controller/OTF is that the Controller can re-tune the motor in real time so that it needs fewer amps/ft-lb depending on operating conditions. Since we do not have to make the compromises associated with a fixed operating point, our 600A Controller can provide better range than a stock OEM 250A unit as well twice the Torque when required.
The Curtis 1268 could also be programmed with 2 different profiles (one for economy use) and it can be switched with a flip of a switch, even on the fly and it will blend the Profiles.

It would however require a dealer with a good technical background to properly configure it.
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Old 03-10-2016, 09:12 PM   #20
Volt_Ampere
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Default Re: Alltrax controller questions

You are still wrong. The field map itself probably doesn't give you any more performance with Alltrax unless the standard controller's map was not good in the first place. Max field current is going to give you max torque but only up to an RPM that can be reached by the available voltage on the Armature. Reducing the field current allows the motor to reach a higher speed with the same applied voltage but at a reduced torque. Therefor the faster you want to go, the lower the field current will eventually have to be.

The equation for this is Armature Voltage = (Kt * RPM) + (Iarmature * Rarmature).

Torque = Kt * Iarmature.

Kt is the field flux and this is proportional to the field current.

If you run a sepex motor with full field current and full battery voltage, it will only spin so fast because the Kt * RPM will limit the current. To spin it faster you have to reduce the field current. That is the purpose of the field map. A good controller will run with as high a field current as possible while achieving the desired speed and acceleration. This is where the motor will be most efficient. Once it reaches full battery voltage on the armature, it has to reduce the field to get more current / RPM.
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