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(2). Double-loop speed control system of the typical working condition
1) Start (or the speed):
ST in the start-up process has been saturated, so that the speed of this loop in the equivalent open-loop state. System only in the constant current loop under the regulation to ensure the motor at a constant current of the maximum allowable under the start-up.
2) slow down (or stop):
ST at this time to reach the output amplitude of the reverse limit. Main circuit current by the bridge is reduced to zero after the inverter. LT and CSR output will soon reach the maximum reverse. CF pulse output to reach βmin, current loop for open-loop. motor torque under deceleration until the motor speed close to the given new value, current loop and speed loop one after another into the closed-loop work, motor in the new value of a given run .
3) Grid voltage fluctuation: This motor because of the larger moment of inertia, which caused the first change in armature current, ST output also did not change the effect of current loop, LT rapidly changing the output so that angle α be adjusted quickly, so the impact on the speed .
4）Small changes in load: in the operation, load changes, will cause the motor speed deviation from the given value. speed up the recovery process and the aforementioned speed (or deceleration) is similar to the process.
2. Common Fault Analysis and Processing
(1) The normal supply voltage, thyristor rectifier output waveform arrhythmia caused by this phenomenon is due to trigger sawtooth slope caused inconsistency. Sawtooth slope adjust potentiometer, the output waveform uniformity could be achieved. in the adjustment process to strike a balance between Qi, this point should be paid attention to the actual debugging.
(2) DC Motor Analysis of mechanical properties of soft thyristor DC motor system, when the current intermittent mechanical properties when the first no-load speed is characterized by high ideals, and the second is characterized by mechanical properties of soft . The so-called mechanical features soft, that is, small changes in load will cause great changes in speed. oscilloscope to observe when using the bridge rectifier output waveform, one may find that missing relative. at this time need to check whether the trigger has pulse output, fast whether the fuse melting, whether the breakdown or thyristor circuit, synchronous transformer is damaged, whether the lack of power. to identify the problems, can be resolved.
(3) The speed of the speed of instability caused by many factors of instability:
1) Electric guns are not firmly fixed or with the host of different axis .
2) The parameters of the speed regulator inappropriate. Respond to the dynamic parameters to adjust (change the ratio of integral parameters ) .
3) Of a speed control system there are(or bad)
4) May be caused as a result of interference. should be found to interfere with the reasons for taking anti-jamming measures.
(4) A little to the set rated motor speed is higher than that should first check whether it is normal for the external control system, such as outside the normal control system, it may be given points, speed regulator, current regulator, such as caused by link failure. Should be cut off the main circuit power supply, only the control system to the electricity, not a given in the case, testing each of the key points (such as the current regulator, voltage regulator, etc. of the potential. and then given together with the former to one by one after each of the key points to check the potential changes, you can find out the fault lies.
(5) Bridge rectifier output voltage is not high stressed 1) the speed regulator and current regulator limiter too small, should be liberalized in accordance with appropriate amplitude threshold .2) than the speed feedback signal, in that they can reduce the rate of appropriate feedback signals.