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Servo Motor Selection
- Nov 24, 2016 -

Ac servo motor

The structure of the ac servo motor stator is basically similar to capacitance split-phase single-phase asynchronous motor. The stator is equipped with two position difference of 90 ° winding each other, one is Rf excitation winding, it always pick on the ac voltage Uf; L, another is the control winding connection control signal voltage Uc. So is also called the two ac servo motor servo motor.

Ac servo motor rotor squirrel-cage often make it, but in order to make the servo motor has a wide speed range, linear mechanical properties, there is no "rotation" phenomenon and the properties of fast response, it is compared with the ordinary motor, should have the characteristics of small rotor resistance and moment of inertia of the two. The rotor current is widely applied structure has two forms: one is using high resistivity of conductive materials high resistivity of the conducting bar cage rotor, in order to reduce the rotational inertia of the rotor, the rotor doing long and thin; Another kind is made of aluminum alloy hollow cup rotor, glass is very thin, only 0.2 0.3 mm, in order to reduce the magnetic resistance of magnetic circuit, should be placed in the hollow cup rotor stator fixed. The hollow cup rotor moment of inertia is small, responsive, and stable running, so widely used.

Without the control voltage ac servo motor, the stator is only produced by the pulse excitation winding magnetic field, rotor motionless. When a control voltage, stator and then produce a rotating magnetic field, the rotor rotate along the direction of the rotating magnetic field, in the case of constant load, the speed of the motor changes with the size of the control voltage, when the control voltage of opposite phase, servo motor will be reversed.

Permanent magnet ac servo motor

Since the 1980 s, with the integrated circuit, power electronic technology and the development of ac variable speed drive technology, permanent magnet ac servo drive technology has the prominent development, all countries well-known electrical manufacturers have launched their own ac servo motor and servo drive series products and constantly improve and update. Ac servo system has become the main direction of modern high-performance servo system, the original dc servo faced the crisis of elimination. After the 90 s, countries around the world have commercialization of ac servo system is controlled using digital sine wave motor servo drive. Ac servo drive unit in the field of drive development with each passing day.

Compared to dc servo motor, permanent magnet ac servo motor main advantages are:

(1) no brush and commutator, so that the work is reliable, the maintenance and low maintenance requirements.

2 stator winding heat dissipation is more convenient.

(3) inertia small, easy to improve the rapidity of the system.

(4) adapted to high speed large torque working condition.

5] with power under a relatively small volume and weight.

Compared with single phase asynchronous motor servo motor

The working principle of ac servo motor with split-phase single-phase asynchronous motor, though similar, but the rotor resistance of the former is much larger than the latter, so compared with the single asynchronous motor, servo motor has three distinctive features:

1, large starting torque

Due to the rotor resistance is big, compared with the ordinary asynchronous motor torque characteristic curve, a significant difference between the two. It can make the critical slip S0 > 1, this not only makes the torque characteristic closer to linear mechanical properties, and has a large starting torque. Therefore, when the stator's a control voltage, rotor rotating immediately, which has the characteristics of starting fast, high sensitivity.

2, has a wide operating range

3, no rotation

The normal operation of the servo motor, as long as out of control voltage, the motor stop immediately. When servo motor loss control voltage, it is in single phase operation state, due to the rotor resistance is big, the rotation of the two opposite directions in the stator rotating magnetic field and rotor effect produced by the two torque characteristics (T1, T2 S1 S2 curve) and synthetic torque characteristic (t-s curve)

The output power of the ac servo motor is 0.1 100 w. When the power supply frequency 50 hz, voltage is 36 v, 110 v, 220, 110 v; When the power supply frequency is 400 hz, the voltage have 20 v, 26 v, 36 v, 115 v, etc.

Ac servo motor smooth operation, low noise. But control characteristic is nonlinear, and the rotor resistance is big, loss is big, efficiency is low, so compared with with the capacity of the dc servo motor, big volume, heavy weight, so is only applicable to 0.5 100 w small power control system.