Understanding the Performance Chart

There are 4 critical points in the performance chart.

1. No Load Speed (N0) – This pertains to the speed of the shaft measured in number of revolutions per minute (rpm) when voltage is applied without any mechanical resistance or load on the motor.
2. No Load Current (I0) – This pertains to the current measured during no load condition of the motor.
3. Stall Torque (Ts) – This pertains to the torque measured when the motor stops rotating due to the increase in load. Please note that it is advisable not to operate at this condition since "demag" or overheating could distroy the motor.
4. Stall Current (Is) – This pertains to the current measured during stall condition of the motor due to the increase in load.

 
Plotting the Performance Chart

1. Speed Line – This is the line that connects the points N0 and Ts, this line identifies the motor’s speed at various conditions
2. Current Line – This is the line that connects the points I0 and Is, this line identifies the motor’s current discharge at various conditions.
3. Output Curve – This curve displays the output power of the motor and can be graphed using the formula: P = (Speed x Torque)/9550  <where speed is in rpm and torque in mNm>
4. Efficiency Curve – This curve displays the efficiency of the motor and can be graphed using the formula: Eff (%) = ((Output Power/(Voltage x Current)) x 100

Main Factors Affecting Motor Performance

1. Input Voltage – Increase in input voltage increases N0, Is and Ts while I0 remains unchanged.
2. Series Resistance – Increase in series resistance will cause Ts, Is to decrease, while I0 and N0 remains unchanged.
3. Number of Winding Turns – Increase in number of winding turns will decrease N0, I0 and Is, while Ts is unchanged.
4. Winding Wire Diameter – Increasing the diameter of the winding wire will increase Ts and Is, while I0 and N0 remains unchanged.
5. Magnetic Flux – Increasing the magnetic flux will decrease N0 and I0 and increase Ts while Is will remain unchanged.
6. Temperature – Increase in environmental temperature increases N0 and I0 while decreases Is and Ts.