Performance Curve XC.xlsx
Calculate the performance of a DC or Brushless DC motor with only four parameters that are easily obtained:
1. Terminal Voltage
2. Terminal Resistance
3. No-Load Speed
4. No-Load Current
Generate a graph with speed, current, output power, and efficiency vs. torque.
Joseph A. Mas, Machine Design, November 24th, 1977
Takashi Kenjo & Shigenobu Nagamori, Permanent Magnet and Brushless DC Motors, 1984
Jon Peltier, http://peltiertech.com/Excel/Charts/TertiaryAxis.html
With the four given parameters (terminal voltage, terminal resistance, no-load speed, and no-load current), you can estimate the performance of a DC or brushless DC motor by calculating its efficiency, torque, and power output under specific operating conditions.
- Terminal Voltage (V)
- Terminal Resistance (R)
- No-Load Speed (ωo, in RPM)
- No-Load Current (Io)
First, let's calculate the motor's speed-torque slope and no-load losses:
Speed-Torque Slope (K): K = (ωo * R) / V
No-Load Losses (P_loss): P_loss = Io * V
Now, you can calculate the motor's performance at a specific operating current (I):
Operating Current (I): Choose a value representing the current under specific operating conditions.
Voltage Drop (V_drop): V_drop = I * R
Back EMF (E): E = V - V_drop
Operating Speed (ω, in RPM): ω = E / K
Operating Torque (T): T = (V - E) * K / R
Electrical Power Input (P_in): P_in = V * I
Mechanical Power Output (P_out): P_out = T * ω * (π / 30) (Convert RPM to rad/s by multiplying by π/30)
Efficiency (η): η = P_out / P_in * 100%
Using these calculations, you can estimate the motor's performance under specific operating conditions. Keep in mind that these calculations are simplified and may not be entirely accurate, as they do not account for factors like magnetic saturation, temperature effects, or complex motor dynamics. However, they can provide a reasonable approximation of the motor's performance and efficiency.
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