BLDC torque equations

Discussion in 'General Electronics Chat' started by wlsx361, Jun 13, 2009.

1. wlsx361 Thread Starter New Member

Jun 13, 2009
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I am working with a BLDC motor and a commercial controller over a range of RPMs from 1500 to nearly 2200. Also the application resides in a hostile environment with temperature as high as 175 deg C. I have the motor manufacturer’s specification but find it hard to come up with the same answers to the torque equations as they do. What is the best equation to use to take advantage of all possible torque corrections with the supplied constants below;

MagnetType SmCo

KTTR 9.9247884 lbf in/Arms Kt at 25°C (phase amps)

TPR 0.4 °C/W Thermal resistance coefficient

AMTEMP 200 °C Ambient temperature

MWINDT 240 °C Max winding temperature (continuous)

TERMVOLTAGE 200 volts Terminal voltage

RTT0 12.505234 ohms Rtt at 25°C

TAUE 1.3435198 ms Electrical time constant

CLDF 0.0045982 lbf in/(rpm)^.5 Damping factor, core loss

NOPOLES 8 - Number of poles

SPEED rpm

PEAKTORQ 25 lbf in Peak torque

POPTEMP 200 °C Peak operation temperature

LTT0 16.801029 mH Ltt at 25°C

E Applied voltage sampled 20 times per second

I Current amps sampled 20 times per second

What would you suggest as a in depth torque equation to use and do I need any other information (parameters) from the manufacturer?

The manufacturer’s peak results
Speed Torque Current [rpm] [lbf in] [Arms] 1800 12.519 1.3132 1850 10.825 1.1355 1900 9.134 0.9581 1950 7.445 0.7810 2000 5.760 0.6042 2050 4.078 0.4278 2100 2.399 0.2516 2150 0.723 0.0759 2172 0.000 0.0000

Last edited: Jun 13, 2009