In order to explain the speed calculation method of DCbrushed
motor from the sampled dynamic current value, the
first thing should be done is to review the basic commutating
principle of DC motor again. Fig. 1 shows part of mechanical
structure of a typical DC-brushed motor. It consists of some
commutators, brushes, and rotor windings [4,8]. The current
flowing into any one of the rotor windings before and after the
commutation process starts is assumed as i and −i ,
respectively. Firstly, because the flowing direction of winding
current would be dynamically changed when the DC motor is
normally working, an induced voltage would be occurred
across the commutated rotor winding at the same time.
Secondly, there is mutual induced voltage will be generated
due to the current variation or commutation process occurred
on the neighboring rotor windings. Thirdly, a rotation voltage
will be generated occurred on the commutated rotor winding
when the commutated rotor winding rotates through the
permanent magnet of DC-motor stator. Therefore, the total
voltage of commutated rotor winding is the
In order to explain the speed calculation method of DCbrushedmotor from the sampled dynamic current value, thefirst thing should be done is to review the basic commutatingprinciple of DC motor again. Fig. 1 shows part of mechanicalstructure of a typical DC-brushed motor. It consists of somecommutators, brushes, and rotor windings [4,8]. The currentflowing into any one of the rotor windings before and after thecommutation process starts is assumed as i and −i ,respectively. Firstly, because the flowing direction of windingcurrent would be dynamically changed when the DC motor isnormally working, an induced voltage would be occurredacross the commutated rotor winding at the same time.Secondly, there is mutual induced voltage will be generateddue to the current variation or commutation process occurredon the neighboring rotor windings. Thirdly, a rotation voltagewill be generated occurred on the commutated rotor windingwhen the commutated rotor winding rotates through thepermanent magnet of DC-motor stator. Therefore, the totalvoltage of commutated rotor winding is the
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