DE3110308A1 - Circuit arrangement for driving a single-phase induction motor such that its rotation speed can be varied - Google Patents

Description

BOSCH-SIEMENS HAUSGERÄTE GMBH 8 Münden, deni7 _# 03.1981 Stuttgart Hochstrasse 17

TZP 81/301 Ka / si / NN

Circuit arrangement for variable-speed control of a single-phase induction motor

The present invention relates to a circuit arrangement for variable-speed control of a single-phase induction motor with capacitively coupled auxiliary winding through alternating current using one with the motor windings triacs connected in series.

Such single-phase induction motors with capacitively coupled Auxiliary winding, which in its speed corresponds to the respectively occurring Conditions to be changeable are used, for example, in dishwashers or the like. In dishwashers the flushing process is influenced as desired with the help of such controllable motors.

It is known to use motors of circulation pumps in dishwashers in to control their speed variably. So it is for example

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wise known (DE-OS 26 46 384) for a start-up phase of the winding of the circulation pump motor a power resistor, preferably a heating resistor to be connected upstream, so that the alternating voltage supplied to the motor compared to the nominal voltage is reduced. This prevents the water jet from suddenly escaping from the nozzle system and reduces the risk counteracts damage to the wash ware. For technical reasons, however, this known measure hardly offers any the possibility of a continuous speed control or a speed control in a variety of stages up to perform maximum speed.

In addition, a circuit arrangement has become known (DE-OS 27 20 958), the task of which is to control the supply voltage an electric motor gradually to regulate the operating voltage, so that a water pump for the rinse water Dishwasher driving electric motor is continuously changeable in its speed. The control of the electric motor takes place via a triac whose control electrode is generated from an oscillator for the time-varying ignition pulses Phase control are fed. The lowering of the supply voltage through phase control A triac is particularly in connection with a single-phase induction motor with a capacitively coupled auxiliary winding problematic.

The present invention is now based on the object of providing a circuit arrangement which allows to control a single-phase induction motor with a capacitively coupled auxiliary winding at a variable speed, with as Switching means a triac is used.

TZP 81/301

A circuit arrangement that meets these requirements is characterized according to the invention that to control the triac circuit elements are arranged, which depending on a present Control signal optionally the triac in each case immediately after a zero crossing of the alternating current for at least controls a full sine wave of this alternating current.

Such a circuit arrangement also fulfills the requirements for speed control of a single-phase induction motor capacitively coupled auxiliary winding in such a way that the connection of the motor takes place only in the zero crossing of the alternating current and this connection takes place over a whole full sine wave preserved. In this way, pulse groups are generated from such full sine waves, which are dependent of an applied control signal can move apart or move closer together. The control signal can be from a fixed program can be supplied, for example, via a microprocessor control or by a control circuit.

According to a preferred embodiment, the inventive Circuit arrangement characterized in that a connected via a threshold value circuit to the alternating current lines, pulse switching element generating one clock pulse with increasing zero crossing of the alternating current one through Control pulses switchable logic circuit connected upstream and that this logic combination circuit for controlling the triac is followed by a time-controlled switching unit is, each with a clock pulse switched through by a control signal via the logic circuit switches the triac through for at least one full sine wave. With the help of this preferred embodiment of the invention Circuit arrangement is in the simplest possible way

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achieved that the switching of the triac in each case small time range is initiated directly after rising or falling zero crossing of the alternating current and is held by the time-controlled switching unit for at least one full sine wave. The timing element in the Time-controlled switching unit can, with regard to the fact that a triac is to be controlled, within a wide tolerance range be dimensioned in such a way that the control pulse for the triac in each case during the duration of the second half-wave, i.e. breaks off in a relatively large time interval. Operating influences thus also have an effect on simple measures for the Timing not disturbing.

It is preferred as a threshold value circuit for clock pulse generation A monostable multivibrator is arranged via a diode path in connection with a voltage divider.

Another monostable multivibrator is a time-controlled switching unit arranged to control the triac. The circuit measures used are simple and easy to use unproblematic switching units ahead. With the help of these measures a cost-effective, functionally reliable Circuit provided which meets the demands placed on it for the variable-speed control of a single-phase induction motor fully meet via a triac.

It is useful to connect an amplifier switching unit between the time-controlled switching unit under the triac. These preferably consists of a transistor circuit.

An embodiment designed according to the features of the invention is described in more detail below with reference to the drawing.

TZP 81/301

Show it

Flg. 1 a circuit arrangement for variable speed Control of a single-phase induction motor and

2 voltage and pulse diagrams occurring in the circuit.

An alternating current is fed to the circuit arrangement (FIG. 1) via the connections L and N, its sinusoidal Voltage curve U is shown in FIG. 2. Via a bridge circuit consisting of a resistor Rl, a resistor R2 and a Zener diode D2, and by switching on a diode Di, the rising zero crossing of the applied supply voltage is established U derived and fed to the clock input of a monostable multivibrator KSl. At the output Q of this monostable Flip-flop KSi is emitted a short clock pulse TI with each rising zero crossing of the supply voltage and a Ünd link UV supplied. The course of the clock pulses TI is shown in Fig. 2 below the voltage curve. From a control input SE, control signals SS are sent as control variables for controlling the speed of the single-phase induction motor to be operated M fed to the AND gate UV. The combination of clock pulses TI and control signals SS by the AND logic element UV results in a pulse-shaped control the clock input of a further monostable multivibrator KS2. This monostable multivibrator KS2 has a timing element on, which generates a control pulse SI at the output Q of the monostable multivibrator KS2, which begins with a through the associated clock pulse TI marked rising zero crossing of the supply voltage and ends within the subsequent second half wave of this supply voltage. Above an amplifier circuit with a transistor T, a triac Tr is controlled, via which the single-phase induction motor M,

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which has a capacitively connected auxiliary winding,

will
controlled ^ The control characteristics of the triac Tr make it possible to set the end of the control pulse within a half-cycle of the supply voltage, ie during a relatively long time frame. A course of the supply voltage UM supplied to the single-phase induction motor M as a function of the supplied control signals SS is shown in the figure.

The control signals SS fed to the control input SE are provided, for example, by a microprocessor control. However, it is also possible to make these control signals available through a tachometer generator.

Claims (1)

TZP 81/301 Claims Circuit arrangement for variable-speed control V- s of a single-phase induction motor with a capacitively coupled auxiliary winding by alternating current using a triac connected in series with the motor windings, characterized in that circuit elements are arranged to control the triac (Tr) which are dependent on a control signal (SS) to optionally control the triac (Tr) in each case immediately after a zero crossing of the alternating current for at least one full sine wave of this alternating current. 2. Circuit arrangement according to claim 1, characterized in that that a clock pulse connected to the alternating current lines via a threshold value circuit (Ri, R2, D2, Di) (TI) at the zero crossing of the alternating current generating pulse switching element (KSi) of a switchable by control signals (SS) logical combination circuit (UV) is connected upstream and that this logical combination circuit (UV) for Control of the triac (Tr) is followed by a time-controlled switching unit (KS2), each with one through Control signal (SS) via the logic circuit (UV) switched through control pulse (Sl) the triac (Tr) for switches through at least one full sine wave. 3. Circuit arrangement according to claim 2, characterized in that a diode path (Dl) in connection with a Voltage divider (Rl, R2, D2) for generating the clock pulse (TI) a monostable multivibrator (KSl) is arranged. TZP 81/301 k. Circuit arrangement according to Claim 2, characterized in that a further monostable multivibrator (KS2) is arranged as a time-controlled switching unit for controlling the triac (Tr). 5. Circuit arrangement according to one of claims 2 to k, characterized in that an amplifier switching unit (T) is connected between the time-controlled switching unit (KS2) and the triac (Tr).