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TBMS-7615-A Motor Performance Curve

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I'm testing TMBS-7615-A motor.

I try to make a performance curve like below which is in catalog of the motor.


I set up MG-set with two of TBMS-7615-A motor.

I'll call one of the motor is M, the other is G.

I use G as a load motor.

I do speed control for M, and do current control for G. 

I mark a maximum load point every 50[rad/s].


As you can see the figure that I made, Under 200[rad/s] which I think under 258[w] condition it works well.

Over 200[rad/s] area which I think over 258[W] condition, It also works well. 

I found that Rated Cont Power is 258[W]. 

Here is my question. 

1. Is the Catalog figure tested under 258[W] condition? 

2. If I control the motor in over 258[W] condition, does motor take a serious damage?  


Minsoo Han


1 Answer

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Answer was provided yesterday by Dan Wolke, in case 1739528.


1. I am guessing your testing with 48VDC? Lower voltage, you will never reach 258 watts.
2. Are you using sinusoidal commutation and not trapezoidal commutation. Most “halls only” drives use trapezoidal commutation to regulate torque. With trapezoidal commutation, you will see a reduction in motor efficiency (about 15% down)
3. The rated power value in our catalog is based on stall condition with 48VDC supply. We calculate that value for comparison without losses. There is no way to reproduce in a laboratory. I have attached two speed/torque curves for trapezoidal and sinusoidal commutation. The actual watts is printed at the bottom of the graph.
4. The motor’s limiting factor for watts has two inputs.
a. Voltage will limit the max speed. When the back EMF of the motor approaches the drive’s VBUS, your current limited and can not increase speed (no torque).
b. Thermal temperature of the copper wire will limits the continuous torque. We want to keep the copper wire ≤130°C at all times. Depending on your motion profile and your heatsink, the amount of continuous current can vary. Our catalog values is based on sinusoidal commutation and a 89mm x 89mm x 6.35mm heatsink
5. Peak current is determined by magnetic flux saturation and can not be altered by environment or external parameters.
6. Damage to the motor:
a. Heat from over current will break down the insolation.
b. High voltage will also break down the insolation
c. Current above our peak current rating can de-magnetize the motor.

One last note: Because we have a ±10% tolerance on each TBM motor’s torque constant (Kt) and/or voltage constant (Kb), our catalog performance values are worst case (lower 10%). When you test your motor, you will meet or exceed the catalog values. But you will not get the exact same performance out of every TBM motor we make. Your motor could be above the catalog Kt and/or Kb rating and the next motor you test will be below the Kt and/or Kb rating.


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