| 摘要 |
<p>The invention relates to a method and an apparatus for the control of a synchronous motor with a permanent magnet or optionally for the control of an asynchronous motor, in particular an asynchronous motor with a shortcircuit rotor. The motor is fed with voltage pulses, where the speed of the motor is controlled by controlling the frequency of the voltage pulses fed, and where the power fed to the motor is controlled in dependence on the speed. The voltage level of the individual voltage pulses is kept constant, while the power fed is controlled by varying the pulse duration, said pulse duration being determined as a function of the frequency, e.g. at a characteristic, a single voltage pulse being fed to the motor during each half-period, said pulse duration being changed by changing the width of this voltage pulse. It is ensured hereby that the number of revolutions of an electric motor may be controlled in a simple manner, thereby obviating the need for having an inverter with voltage control, and obviating the need for performing measurements of motor current and number of revolutions like in the prior art. The invention may particularly be used for operating a liquid pump, e.g. a pump for pumping water in an aquarium.</p> |
