Scientific paper ID 2133 : 2021/3

Often in the research work or in the activities of repair and commissioning it is necessary to experimentally evaluate some important parameters of a DC electrical drive such as the resistance of the motor armature Ra and the coefficient of electromagnetic interaction . Experimental measurement of the resistance Ra is complex and with many disadvantages: the drive must be subjected to a relatively low supply voltage with the excitation removed or with a locked rotor, a conditional value of the voltage drop in the transition ”contact brushes - collector” is accepted, which in the real case may differ, as it depends on the state of the transition, The resistance of the armature Ra can be determined approximately by assuming that at rated load the energy losses in the resistance of the armature winding are nearly half of the total power losses in the motor.

The report proposes another approach for determining the parameters Ra and cϕ. This method consists of using objective measurements and guarantees very high accuracy, avoiding the main disadvantages of the classical method. The current in the armature, the angular speed and voltage are measured. Then, from the equation for the equilibrium of the electromotive voltages, the d parameters for the different ways of speed regulation are determined. The performed simulation in Simulink environment verifies the developed methods as much more accurate and fast than the classical ones.