Actually I work for a company writting software for dynamometers. This research is partial hobby (for the e-ATV), and partial for investigation about the needs of dynamometers when used with electric motors. Torque and Power are the basic variables you get in a dynamometer, even for an inertial dyno (with the suitable amount of mass). For this project I used SP5 DAQ (braked) that also controls an eddy current brake and acquires load cell (torque). This allows me to sweep tests but also stationary tests (rpm constan)
The purpose of a standard dynamometer is normally measuring HP and TQ, but with electric motors I think the next interesting variable is efficiency. For that purpose in some tests I acquired battery voltage and current (Curtis+Motor is considered a black box) and then with the battery power (V*I) and mechanical power (KW) it is easy to calculate efficiency.
This induction motor had a peak of about 86%, but I didn't finish the software for creating a whole map, so I cannot be sure if there is another peak somewhere- Anyway 86% is good for me. And also, keep in mind that when driving the motor to max torque it can decrease up to 65% or so.
And regarding the question about torque, normally with electric motors there is a direct relationship between current and torque. But with induction motors it also changes with slip (difference between mech speed and electric speed), so you will need some dyno if you want to have the resulting torque.
And regarding the graphs, I still have doubts about what is the true nominal speed. According to my calculations it should be around 2000 rpm as stated in the previous post. Indeed as you can see how torque decreases from this point, since the inverter has no more available voltage to follow the increasing speed, then current starts to decrease. But somehow the inverter is able to still increase the power up to 3200 rpm (other motors have flat power at this point), and then it quicly falls in THIS test, but when performing a slow sweep from 3200 to 3700, I can see that the inverter little by little is able to increase AGAIN the torque, and provides a no so deep fall
Another interesting fact: I think the actual TQ graph from 0 to 2000 rpm should be almost flat, but the inverter needs more time to adjust its PIDs, it does not behave in the same way during an acceleration transient
How much Amps can your inverter handle?
udaykishanr wrote: e-vektor wrote:
I finally got the Curtis 550A controller to work: I had to ask Curtis distributor for the VCL package, prepare an empty project, compile it, upload the firmware... but it finally worked
And I finally got some time to do the final test with 8 LIPO batteries charged up to 96V (arranged in couples to give 32 Ah * 10C discharge)
This is the final result: 36 HP at about 3200 RPM. Nominal RPM is about 2000 RPM with 27.3 HP and a pretty good torque peak of 95 N*m.
From this point torque stars to fall, although power still increases up to 3200 RM.
With these 8 battery pack the voltage drops up to 80V at the power peak. I guess that with 3 LIPO in parallel (12 total) the voltage would drop a bit less and then it would be about 37 or 38 HP, but with these batteries and motor it seems it cannot go farther
Efficiency at the power peak was about 75% (induction motors are more efficient at parcial loads). With a magnets motor like ME1304
, controller's delivered power could be the same, but they should achieve 90 or 92% efficiency, and thus power at shaft would be may be close to 45 HP, but I don't think it can be more at this voltage.
I finished building my own inverter to run this motor by using a Mitsubishi MOSFET pack. I generated 3 phase signals to these MOSFETs by using a logic circuit which involves a Shift Register.
Now then, The motor is running with a 2nd order fan load.
But, I am confused how to track the torque speed characteristics of this motor.
Could you please tell me how you are doing this? I really like the way you are presenting in a graphical manner. How to arrive at this?
Well, to say furthermore about my application I am working on... I would like to lock onto the peak point of Torque curve for certain time period by using feedback signal from the rotor.
To do this I need to monitor Torque curve of this motor.
By the way thanks for this clue. Will try to dig deep into it. Furthermore information is appreciated
Thanks a lot