Servo motor based on electromagnetic rule, when the magnetic field changes, the adjacent conductor can produce inductive electromotive force, the direction of fit Faraday law and lenz law, and the original at the end of the coil voltage on the contrary, the voltage is the counter electromotive force. In permanent magnet synchronous servo motor, as long as the motor in the scroll, there will always be cut coil magnetic field lines, so there will be a counter electromotive force. Counter electromotive force in E1, the RMS calculation is as follows: meanwhile, KE— —To share constant; FN -—As the frequency of the stator current; NL——As the number of turns of the stator winding of each phase; ф— —Give priority to the amplitude of magnetic flux values. A determinants, counter electromotive force, the rotor angular velocity of rotor magnet magnetic field planning, the number of turns of the stator winding when motor rotor magnetic field and the number of turns of the stator winding is determined, and only decided to counter electromotive force factor is the rotor angular velocity, may say is the rotor speed, with the increase of rotor speed, the counter electromotive force also will increase. Second, the counter electromotive force test way of communicating based on permanent magnet servo motor general technical conditions, we usually use counter electromotive force constants for inspection of permanent magnet synchronous motor. Back emf constant is the permanent magnet synchronous motor is a very important technical parameters, it is related to the motor operation performance and the planning work of the controller. Therefore, in the permanent magnet synchronous servo motor production it is necessary to accurately test the parameters and through specification testing to verify whether planning products meet the technical requirements. GB/T 50349 permanent magnet communication servo motor general technical conditions in the rule will be tried first motor to the rules of technical conditions of a certain rotational speed n, then use the oscilloscope observation its waveform, calculated by voltage and speed counter electromotive force constants (柯), and it requires Ke rules with permanent magnet synchronous servo motor technology conditions. Chart 1: counter electromotive force test channels as shown in the above channels for permanent magnet synchronous servo motor counter electromotive force test, according to the experiment with test motor for electric operation specification requirements, drag the participants motor no-load running speed to n; By the test, the rotational speed sensor end of WP4000 frequency conversion power analyzer counter electromotive force U test subjects motor end line. Experiment acquisition motor no-load speed of n line counter electromotive force U, counter electromotive force was calculated by the type under constant, to verify whether meet the technical requirements for constraint scale. Type: Ke— —Counter electromotive force constants, the unit of volt per radian negative power seconds (V/rad*-1 ^ (s)； U——Motor line counter electromotive force, the unit is v (V)Twisted counter electromotive force of RMS, sine wave driving motor, square wave drive motor wire counter electromotive force amplitude; N——By the speed of measuring points and transfer unit is per minute (r/min)。 This scheme use WP4000 frequency counter electromotive force and speed test of the rf power analyzer, the adoption of effective synchronization technique to ensure the electric parameters and the parameters of synchronous test. Open, WP4000 frequency conversion power analyzer raw data port, front end to collect the original waveform data can directly is Shared with PC through the Ethernet, can completely replace the demand of the oscilloscope. After completion of custom analysis software can directly counter electromotive force constant test, meet the demand of experiment in servo motor system automation test.
