I would to identify efficiency, voltage, current for a particular Brush less DC motor in our lab given characteristic curves.
Electrical specifications are
The operating conditions are
Torque: 0.35 N.m
RPM : 1200
Based on the operating condition, i drawed one more torque vs speed line (orange color) passing through 0.35 N.m & 1200 rpm and keeping slope constant.
To explain the image
Horizontal axis (X) : Torque (N.m)
Left Vertical axis : U(V) - Applied voltage - Light Blue color
I(A) - Current - Green color
P1(w) - Electrical power input - Dark Blue color
Right Vertical axis : n(r/min) - Revolution per min - Orange color
P2(w) - Mechanical power output - Red color
Eff(%) - Efficiency - Brown color
Unfortunately, i don't have better quality image. Please click on the image or Zoom the browser page to enlarge a bit more.
I have drawn few vertical and horizontal dashed lines(pink in color) passing through the operating point (0.35 N.m and 1200 rpm).
Question:
As the voltage vary the torque vs speed curves, does the efficiency curve vary ? what about the voltage and current ?
What are the approximate values in my case ?
Current = 8 Amps ?
Voltage = 15.00 or 17.50 V ?
Efficiency = 50 % ?
Thanks
Best Answer
Yes
Motor Specs
Max Eff.= 52.2% @ 5.916 A, 2999 RPM , 0.236 N.m
Your operating specs:
What are V,I,Eff.? :
Using Max Eff.,
\$\dfrac {0.236 Nm}{0.436}(=54\%) \cdot 24V = 13V, ~~2999 ~RPM \cdot 54\% =1619~RPM\$
which is much greater than torque ratio 54% at peak eff.
Iss=80.3%*9.427 = 7.57 A and power Pe = 98.4W = 7.57A⋅ 13V
You will need a tach to regulate the RPM if you use this to vary the BLDV voltage or some other servo method.