What determines the torque of a brushless motor?

What determines the torque of a brushless motor?

Since torque is a function of current in a brushless motor, and current is equal to the voltage drop in the circuit divided by the circuit resistance, when the back EMF is equal to the forward applied voltage minus the circuit losses the functional torque of the motor will reach a point where it runs out of the torque …

Does current affect motor torque?

In general for permanent magnet motors the torque produced will be proportional to the current flowing through armature and the no-load speed will be proportional to the voltage.

How does torque relate to current?

Electrical motor torque is proportional to the product of magnetic flux and the armature current. Motor current varies in relation to the amount of load torque applied. When a motor is running in steady state, the armature current is constant, and the electrical torque is equal and opposite of the mechanical torque.

How much current does a brushless motor draw?

Typical power output of a 25 size motor is 0.66 BHP using a 9in x 6in (225mm x 150mm) propeller turning at approximately 10,000 RPM. 0.66 BHP / 1.5 = 0.44BHP x 750 = 330 watts Using a 3S 11.1v Lipo battery the current draw to produce 330 watts = 330 Watts / 11.1 Volts = 29.7 amps.

How much torque does a brushless motor have?

Brushless motors are capable of producing more torque and have a faster peak rotational speed compared to nitro- or gasoline-powered engines. Nitro engines peak at around 46,800 r/min and 2.2 kilowatts (3.0 hp), while a smaller brushless motor can reach 50,000 r/min and 3.7 kilowatts (5.0 hp).

What is the efficiency of a brushless motor?

Brushless motor efficiency is very high in comparison to any combustion engine with values averaging between 70% and 90%.

What determines motor current?

The current depends on internal friction of bearings and brushes and wind/fan effects, as well as depending on the amount of work (wattage) the motor shaft is performing. With DC motors, the RPM of the shaft is proportional to the drive voltage and the generated voltage.

What is motor torque current?

Torque current is the portion of the total current to the motor that is in phase with the output voltage. Flux current, simplistically described, is the portion of the total current which magnetizes the motor. The efficiency of any motor will improve if more of the total current is in phase with the output voltage.

Is torque directly proportional to current?

Hence torque is directly proportional to square of the armature current. In dc series motor at saturation condition, flux is constant. Hence torque is proportional to armature current.

How is brushless motor current calculated?


  1. Imax= sqrt(V Io/Rm) Torque at max efficiency:
  2. Ip= (V + Rm Io)/(2 Rm) Torque at max power output.
  3. MOTOR MAXIMUM EFFICIENCY: (Better mechanical output to electrical work ratio) η max= [1- Sqrt ( Io Rm / V )²]

How is brushless motor current measured?

Ensure there is no mechanical connection on the output shaft. Connect your LiPo battery up to the ESC with the ammeter between one lead of the battery and the ESC. Set your ammeter to measure current. Double check the leads are in the correct spot to measure current up to 10A.

How is motor torque calculated?

To calculate load torque, multiply the force (F) by the distance away from the rotational axis, which is the radius of the pulley (r). If the mass of the load (blue box) is 20 Newtons, and the radius of the pulley is 5 cm away, then the required torque for the application is 20 N x 0.05 m = 1 Nm.

What are the benefits of a brushless motor?

Brushless motors offer other advantages over brushed DC-motors, including higher reliability, longer lifetime (no brush erosion), elimination of ionizing sparks from the commutator, and overall reduction of electromagnetic interference. Motors that are brushless are considered more efficient than brushed DC-motors.

What are the features of a brushless motor?

No contact between commutator and brushes meaning the motor has long life

  • Able to run at high speeds
  • Excellent tracking and responsiveness
  • Requires a drive circuit
  • Tends to have a higher overall cost
  • Do you have to break in a brushless motor?

    No need to break in a brushless motor. The reason you should break in a brushed motor is because you want the brushes to wear smoothly to the commutator so they provide the best contact which maximizes its efficiency and also helps prevents premature wear. A brushless motor does not have brushes to wear in like the brush motor.

    What is the maximum torque on the motor?

    Starting torque is the maximum torque that can be produced by a motor in order to start rotational movement of the load. Stall torque is the maximum torque that can be applied to the shaft and cause the motor to stop rotating.


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