Controller Mapping

[mjroman20]

There are two important things about field maps I have learned from manufactures.

1) The provided plotted data they may provide is not by any means the most efficient. Rather it is the "absolute limits" of performance the motor can do. There is usually some additional data that has efficiency ratings per Current:RPM:Torque ratios...certainly you could map to this to increase run time.

2) Designing these curves is just as much an art is it is a science. There seems to be a lot of judgement and observation calls based on audible and visual ques. Something I plan to be working on in the near future.

[scottyb]

It is impossible to factor in human error. When the operator has the option to select field current parameters they also have the responsibility to select correctly or not to simply forget to make a change when the load requires it. This is the pitfall I see in selectable field parameters. Which is why the stock control is so detuned that it rarely if ever allows the motor to heat up... in fact the control is most likely to burn up way before the motor in a stock drive system.

[Sergio]

mjroman20, here is the Field Weakening map I posted for the Club Car stock motor:

http://www.buggiesgonewild.com/attac...ning_curve.jpg

and To Your point, I am attaching the motor data for the Max Field current, which shows the relationship of the different variables, including the efficiency.

ScottyB, I am pretty sure from previous discussions about the Torque Controller that those knobs do not directly affect the Armature or the Field Current.

They simply provide input to the Controller so it can adjust the parameters as needed to deliver the experience the operator is trying to achieve.

I thought You posted not long ago that Alltrax was trying to develop a similar setup ( real time controller parameter changes) for their XCT line of Controllers.

[mjroman20]

The one fact about the mapping that still blows my mind is what the stock EZGO and ClubCar controllers typically run 2A or lower when in "Freedom" or "Mode 4" When the manufacturer data for those very motors have a minimum field of 3~5A.

Though I was once told if the relationship between the field and armature current is maintained in the proper ratio when operating below this it would behave much like a series motor. Ultimately you could potentially drive the field down to near 0 without damage if done correctly. Though at this point I'd have concerns about the calibration tolerances on the field drivers when trying to dial in specific values in the ranges of 1/10s of an amp.

[greg-g]

Originally Posted by mjroman20

The one fact about the mapping that still blows my mind is what the stock EZGO and ClubCar controllers typically run 2A or lower when in "Freedom" or "Mode 4" When the manufacturer data for those very motors have a minimum field of 3~5A.

Though I was once told if the relationship between the field and armature current is maintained in the proper ratio when operating below this it would behave much like a series motor. Ultimately you could potentially drive the field down to near 0 without damage if done correctly. Though at this point I'd have concerns about the calibration tolerances on the field drivers when trying to dial in specific values in the ranges of 1/10s of an amp.

I would like to see where you got this info of going to or below 2 amps on the field

[Volt_Ampere]

The only reason to reduce field current is to get more motor speed. You want to run the field current as high as possible while still drawing enough Armature current to get the motor speed you want. The motor speed with full field won't be very high but that is when you get maximum starting torque. As speed increases, the max Armature current drops due to the BEMF generated. To reduce the BEMF you have to reduce the field current. This is a SEPEX motor.

With a Series motor, the field current drops as the armature current drops because the armature and field are in series. This allows the motor to have high starting torque at zero RPM and as the RPM increases and the Armature current decreases, the field current also has to decrease. That is why if you run a series motor with no load it will keep spinning faster until it most likely comes apart. A SEPEX motor will just go to it's no load RPM which won't be all that high with full field current.

[greg-g]

Originally Posted by Volt_Ampere

The only reason to reduce field current is to get more motor speed. You want to run the field current as high as possible while still drawing enough Armature current to get the motor speed you want. The motor speed with full field won't be very high but that is when you get maximum starting torque. As speed increases, the max Armature current drops due to the BEMF generated. To reduce the BEMF you have to reduce the field current. This is a SEPEX motor.

With a Series motor, the field current drops as the armature current drops because the armature and field are in series. This allows the motor to have high starting torque at zero RPM and as the RPM increases and the Armature current decreases, the field current also has to decrease. That is why if you run a series motor with no load it will keep spinning faster until it most likely comes apart. A SEPEX motor will just go to it's no load RPM which won't be all that high with full field current.

were you answering my question if so take a look at the field map Sergio posted there is so much more to a sepex motor but you hit the basics again do not go below or to the right of the map.

I believe they do not go below or close to 2 amps

[mjroman20]

Originally Posted by greg-g

I would like to see where you got this info of going to or below 2 amps on the field

From digging into some of the software on the Curtis controls, specifically field mapping parameters.

Additionally I have done some current testing in a cart with a stock setup. Data collected with a DEWE data acquisition unit, and plotted out in MATLAB.

The plot attached is specifically for freedom mode, on a EZGO PDS 36V with a 1206MX controller.

[mjroman20]

Also this...from a 1510 stock clubcar IQ control.

[Volt_Ampere]

Can you get field current and armature current vs RPM? That will show how the field weakens as your RPM increases.