The effect can be eliminated by means of Ri compensation, which
essentially entails measuring the motor’s current consumption, relating
this to the motor’s instantaneous drop i across Ri, and increasing the supply voltage accordingly.
The load current is measured as the drop across sensing resistor R3. For optimum results, this impedance must be kept about equal to that of the motor. Figure 2 shows the practical circuit of the motor driver based on a power operational amplifier.
Simple DC operated motors with a permanent magnetic stator behave as an independently energized motor. The speed of an ideal motor with an, infinitely low internal resistance is in direct proportion to the voltage applied, irrespective of the torque.
The motor thus runs at a speed at which its reverse electromotive force (e.m.f.) equals the supply voltage.
The reverse e.m.f. is directly proportional to the force of the (constant) magnetic field, and the motor speed.
In theory, therefore, the motor speed can be held constant with a constant supply voltage. The speed reduction observed in practice arises from the voltage drop across the internal resistance, Ri, of the armature winding. Thus, when the motor is loaded, its current consumption, and hence Vai, increases, reducing the effective supply voltage.
The Type Ll65 £rom SGS can supply up to 3 A at a maximum supply voltage of 36 and is therefore eminently suitable for the present applications. cation. Capacitors C1 and Cz suppress noise on the reverse e.m.f. from the motor.
The basic set-up of the supply required here is shown in Fig. l.
In· fact, this calls for a voltage source with a negative output impedance, since it caters for a higher output voltage when the . load is increased.
Due care should be taken, however, in so l extending the circuit, because this readily leads to instability. The motor itself already forms a fairly complex load, since the revolving rotor winding is mainly inductive, and the rotor itself represents a fairly large capacitance.
Simplest DC Motor Speed Controller Circuit Diagram:
The load current is measured as the drop across sensing resistor R3. For optimum results, this impedance must be kept about equal to that of the motor. Figure 2 shows the practical circuit of the motor driver based on a power operational amplifier.
Simple DC operated motors with a permanent magnetic stator behave as an independently energized motor. The speed of an ideal motor with an, infinitely low internal resistance is in direct proportion to the voltage applied, irrespective of the torque.
The motor thus runs at a speed at which its reverse electromotive force (e.m.f.) equals the supply voltage.
The reverse e.m.f. is directly proportional to the force of the (constant) magnetic field, and the motor speed.
In theory, therefore, the motor speed can be held constant with a constant supply voltage. The speed reduction observed in practice arises from the voltage drop across the internal resistance, Ri, of the armature winding. Thus, when the motor is loaded, its current consumption, and hence Vai, increases, reducing the effective supply voltage.
The Type Ll65 £rom SGS can supply up to 3 A at a maximum supply voltage of 36 and is therefore eminently suitable for the present applications. cation. Capacitors C1 and Cz suppress noise on the reverse e.m.f. from the motor.
The basic set-up of the supply required here is shown in Fig. l.
In· fact, this calls for a voltage source with a negative output impedance, since it caters for a higher output voltage when the . load is increased.
Due care should be taken, however, in so l extending the circuit, because this readily leads to instability. The motor itself already forms a fairly complex load, since the revolving rotor winding is mainly inductive, and the rotor itself represents a fairly large capacitance.
Simplest DC Motor Speed Controller Circuit Diagram:
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