Thank you for your replies. Let me see if I am understanding them correctly.
liveforphysics's explains that the right current for best efficiency at a specified RPM has to do with the balance between core and winding losses.
spinningmagnets points out that the hotter the copper windings get, the more resistance they have. This implies that the balance between core and winding losses will change and thus the best efficiency current at a specified RPM will change with motor temperature.
I wanted to explore this more, so I went to ebikes.ca and their great motor simulator tool (Thanks Justin and company!).
https://ebikes.ca/tools/simulator.html
I set Human Power to 0 and X axis to RPM. Otherwise, no other changes. I selected Run Simulation Set, with Throttle as the variable (since this will vary the current), between 80% to 90% and 11 simulations and checked All Data. I downloaded the results and dropped them into Excel.
Next, I clicked on Show Advanced and changed motor temperature from 60 C to 200 C. I then ran the same simulation set, downloaded the data, and put it on another page in my Excel file.
Using a fairly randomly chosen 285 RPM, I discovered that at I got best efficiency at 16.06 amps (80.958%) for the 60 C page. (Row for those of you playing at home).
Finding the best efficiency for the 200 C page, I found that the best efficiency was less, and it was at a different current: 78.465% at 14.25 amps.
So, to my question: What about motor temperature? Would that change the RPM/current curve?
The answer is yes. So, if I want to match my current to RPM for best efficiency, I need to correct for Motor Temperature.
I also asked: Does Load change this curve?
I go back to the Motor Simulator Tool. I reset Motor Temperature to 60 C. I set Grade to 30% since going uphill will increase the Load. I run the same Simulator Set, download, and put it in a new page.
The load has increased from 436 W to W but the efficiency and current for that efficiency has not changed.
Answer: Load does not change the RPM/current curve.
My other question was Does Voltage change the curve?
I reset Grade to 0. I change Battery to Custom Battery and accept the default of 38 Volt, .2 Ohm, 8 Amp hour and run the simulator set. Download, put in new page.
Then I modify only the Custom Battery Voltage to 36 volts, run the simulator set, download, and put in new page.
This time I use 249 RPM.
For 38 Volts, I get the best efficiency which is 79.749% at 18.15 amps. (Row )
For 36 Volts, I get the best efficiency which is 80.254% at 14.70 amps. (Row )
Does Voltage change the curve? Yes.
So my conclusion is that if I want to accelerate matching the current to the RPM for best efficiency, I must also correct for Voltage and Motor Temperature but I can ignore load.
Does this make sense? Have I missed anything else I should be correcting for?
Link to Wing Flying
If you are looking for more details, kindly visit motor speed.
rpm is the motor's base speed.
rpm is the motor's maximum rated speed, with a fully weakened field.
I would expect about 18.3 amps for the armature (at 480 volts) for this 10 HP motor, as the GE motor for my 10EE is rated 5 HP, 230 volts for the armature, and about the same current.
Usually, the field voltage is one-half the armature voltage, which would be 240 volts in this case.
But, also note that the there are two current values.
One may be for a 240 volt field, with the two windings connected in parallel; the other may be for a 480 volt field, with the windings connected in series.
70 volts for the field may be its fully weakened voltage. That might be the correct value for operation with a 240 volt field. It would be twice that with a 480 volt field.
That the nameplate data states "1 HR. M.TOOL" indicates that this is intended for machine tool duty.
Surging or running away is an indication that the series field is incorrectly connected.
But, this motor doesn't state "SPEC. COMP. WOUND", which these machine tool motors usually do if they are, indeed, compound wound.
My guess is an examination of the leads in the connection box will show two very heavy leads designated A1 and A2.
And, either four leads designated F1, ..., F4; or six leads, with four designated F1, ..., F4 and two leads designated S1 and S2.
Dc drive is so good, its a shame to abandon it, unless the drive electronics are unsalvageable.
My 10EE's 5 HP motor states the same, and from which I am drawing some of my conclusions.
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