Electricity: motive power systems – Synchronous motor systems – Armature winding circuits
Patent
1992-08-20
1994-08-02
Ro, Bentsu
Electricity: motive power systems
Synchronous motor systems
Armature winding circuits
318722, 318724, 318432, 318254, H02P 602
Patent
active
053349210
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on a circuit arrangement for operating a synchronous motor of the type defined in the preamble of claim 1 and including a multi-phase armature winding in a direct voltage network.
In a known circuit arrangement of this type for a three-phase synchronous motor (DE 3,940,569) the switching signals are configured, in order to reduce commutation noise and radio interference, so that the two switching signals for the semiconductor switches associated with the commutating winding phases overlap one another in time. In the overlap region, one of the two switching signals is clocked in such a way that the average of the phase current increases in the up-commutating winding phase and decreases in the down-commutating winding phase, namely linearly or according to an exponential function. However, this type of commutation requires relatively high expenditures for circuitry.
SUMMARY OF THE INVENTION
In contrast thereto, the circuit arrangement according to the invention including the characterizing features of claim 1 has the advantage of low expenditures for circuitry with relatively little commutation noise and very low radio interference which makes additional interference suppression measures unnecessary. During the commutation, that is, during the transition of the current from the one winding phase to the other winding phase, the analog control of the semiconductor switches has a positive effect in that only a slight current steepness occurs. This again causes only slight excess voltages so that inverse diodes and voltage limiters are not required. Because of the absence of the steep switching edges, there is also hardly any radio interference and the commutation noise is noticeably reduced.
The measures defined in the further claims permit advantageous modifications and improvements of the circuit arrangement defined in claim 1.
According to a preferred embodiment of the invention, the reference signal is picked up as a voltage drop across a resistor through which flows the phase sum current of the armature winding and is suitably amplified.
The circuit arrangement according to the invention can be employed for synchronous motors in which the winding phases of the armature winding are connected in a wye configuration, independently of whether the neutral point is brought out or not.
If the neutral point is brought out, a so-called half-wave control can be realized if, according to one embodiment of the invention, a semiconductor switch is connected in series with a respective winding phase and the parallel series connections are connected with the direct mains voltage, on the one hand, by way of the neutral point and, on the other hand, by way of the resistor which picks up the winding sum current.
A so-called full-wave control can be realized if, according to a further embodiment of the invention, pairs of semiconductor switches are connected in series and a winding phase of the armature winding is connected at each one of their respective connection points. This results in a number of parallel series connections which correspond to the number of winding phases or conductors. The parallel series connections are connected jointly to the direct mains voltage by way of the resistor for picking up the sum current in the armature winding. This full-wave control improves motor utilization. The number of phases in the armature winding is not subject to any limitations. If a three-phase winding is involved, the armature winding may also be connected in a delta configuration.
In a preferred embodiment of the invention, an operational amplifier, more precisely a differential amplifier, is employed as the difference former and a power MOS field effect transistor (power MOSFET) is employed as the semiconductor switch. This results in a low-power transistor actuation.
According to a further embodiment of the invention, the edges of the periodic rectangular pulses of which the switching signals are composed are sloped at an angle less than 90.degree. so that the ascend
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Ro Bentsu
Robert & Bosch GmbH
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