Dc motor can use magnetic flux, and change the armature voltage regulator circuit resistance method of speed adjustment, but the change the armature resistance speed control circuit to get the mechanical properties of soft, so rarely used on nc machine tool, and USES the voltage regulator and the magnetic method of combining the two methods, not only can obtain a wide speed range, can make full use of the capacity of the motor. In the nc machine tool spindle drive, dc spindle motor speed control usually USES the thyristor speed control system and the transistor pulse width modulation (脉宽调制)Speed control system. A, the magnetic spindle motor speed regulation circuit power is larger, and require constant power speed range as large as possible, so commonly used separately excited motor, excitation winding and armature winding are independent of each other, by a separate adjustable dc power supply. Control circuit of excitation current is given, the armature voltage feedback, excitation current feedback PI regulator after comparing three groups of signal input, the output of the regulator through the voltage/phase converter, control of thyristor trigger pulse phase, adjust the current size of exciting winding, realize the constant power weak magnetic speed of the motor. Second, the pressure regulating speed regulating speed control circuit is similar to dc feed servo system, is also made of the speed loop and current inner ring double closed loop speed regulation control system, has good static and dynamic index, can use the overload capacity of the motor in large degree, the transition process. Through the control of dc variable speed spindle motor armature voltage implementation. Three, the main circuit and working principle of the nc machine tool parts, require spindle positive &negative cutting power should be as large as possible, to stop and change quickly. Spindle dc motor driving device adopts three-phase bridge type anti parallel logic and circulation reversible speed control system. The main circuit is shown in figure 1. Each set of connected in three-phase bridge type inverter bridge formation, two groups for reverse polarity parallel converter bridge, by an ac power supply. Reverse polarity parallel circuit can realize motor positive and negative feedback to electric and dynamic braking. To ensure that at any time only allow a group of bridge road work, another bridge road block, the logic control circuit. When the motor forward movement, VT1 pipe work in rectifier state, provides the positive direct current; Motor reverse movement, VT2 pipe work in rectifier state, and provide reverse direct current, motor in a starting, speed control, three quadrants. From forward motion to turn to reverse when motor electric state, speed instruction from is becoming negative, inverter VT1 tube into the state, the motor armature inductance energy storage to maintain current in the circuit direction remains unchanged, still in a state of electric motor, the armature current has been gradually decreasing. When the armature current reduce to zero, must make VT1 pipe and VT2 is blocked, then free to rotate the motor in the inertial effect. After security delay VT2 tube into the active state of inverter, motor working in state feedback power brake, the mechanical energy back to the grid, speed decreases rapidly, after the speed drop to zero, VT2 rectifier tube into the state, reverse starting motor, so as to complete the work from a quadrant to the third quadrant of the conversion. Just make VT1 pipe and VT2 instead of control, it has realized the motor from the inversion to the forward transformation process. Four, the main circuit control requirements to ensure that at any time only allow a group of bridge road work, another group of bridge road block, the logic control circuit. Using the logic control circuit detects whether the armature current of the circuit to zero value, and judge the direction of rotation, provide VT1 pipe and VT2 is allowed to open the signal, make a set of thyristor at work, another group of thyristor trigger pulse were blocked, so as to cut off the positive and negative between two groups of thyristor current path that may occur. For this reason, logic circuit must satisfy the following conditions: (A)Every moment only allowed to offer a set of thyristor trigger signal. (2)Only when the work that a group of thyristor after current zero, to cancel the trigger signal, in order to prevent when thyristor inverter, current is not zero, cancel the trigger signal caused by inverter subversion malfunction. (3)Only when the work that a group of thyristor is completely closed, can provide another set of thyristor trigger signal, to prevent big circulation. (4)Any set of thyristor conduction, to prevent the output voltage and motor winding electromotive force produced in the same direction, lead to too much electricity. This paper from paper net
