Contents
What is continuous current in dc motor?
Continuous rated current is the current the motor can continuously run at for a given voltage such that the temperature of the motor windings doesn’t exceed the rated temperature of the insulation class of that motor. The current at this steady-state point is the continuous rated current.
When the load condition is constant the speed of a DC motor is affected by?
The flux decrease due to the armature reaction is negligible under normal condition. If load change is not considered since a DC shunt motor has a constant flux φ and a constant supply voltage the speed of the motor remains constant.
What’s the relationship between current and DC motor?
To further simplify the torque equation, the number of poles (P), the number of coils (Z), and the geometric factors (2πA) can be combined to form the torque constant, k T, which is specific to the motor. This simplifies the torque equation to:
How is the friction torque of a DC motor calculated?
In practice, the motor friction torque MR is determined multiplying the torque constant kM of the motor and the measured no-load current I0. The torque vs. speed line and the torque vs. current line are then started not at the left vertical axis, but at an offset on the horizontal axis equal to the calculated friction torque.
This simplifies the torque equation to: For most DC motor cases, we can assume the flux, φ, is constant, making torque directly proportional to the current: When examining the torque-current curve for a DC motor, notice that the no-load (stall) current is greater than zero.
How to calculate the resistance of a DC motor?
It is also useful at this point to measure the terminal resistance of the motor. Measure the resistance by contacting the motor terminals with an ohmmeter. Then spin the motor shaft and take another measurement. The measurements should be very close in value. Continue to spin the shaft and take at least three measurements.