DE2217847A1 - CIRCUIT ARRANGEMENT FOR REVERSING THE DIRECTION OF ROTATION OF AN ELECTRIC MOTOR, IN PARTICULAR A WASHING MACHINE - Google Patents

Description

Dr-In HAWS RUSCHKE

April 33, 1972

Whirlpool Corporation Administrative Center Benton Harbor, Michigan 49022 / USA

Circuit arrangement for reversing the direction of rotation an electric motor, in particular a washing machine

The invention relates to a circuit arrangement for reversing the direction of rotation of an electric motor, in particular one Washing machine.

The known drive devices for automatic washing machines with alternating direction of rotation of the agitator generally have transmissions that are one in one direction convert the active movement of a motor into the desired reciprocating oscillating movement DC motors used for various direct drive systems »which have the disadvantage that a relatively

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agile control circuitry is required to perform the desired stirring and spinning operations. Besides that is in the known arrangements for automatic washing machines, an energy storage device between the Power source and the agitator required.

The different arrangements for reversing the direction of rotation of single-phase motors have a number of disadvantages when they be used for washing machine drive systems that require frequent periodic reversals of direction. These Disadvantages include the following: overheating of the engine as a result of operating it for long periods of low efficiency and low, non-self-ventilation Speeds; short switch life; high costs because of the large capacitors, switches, complicated feedback circuit and additional ventilation devices; difficult making one Application system that has good stirring and centrifugal properties having.

The invention is therefore based on the object of an improved drive system, in particular for automatic To provide washing machines in which a reverse induction motor is used to directly drive an agitator. The drive system should have a control circuit for rapid, controlled, periodic reversal of the direction of rotation of the motor.

This object is achieved according to the invention by input lines for an alternating voltage which has zero crossings, a rotor, a first and a second Stator winding, which is inductively coupled to the rotor,

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wound in opposite directions tmd connected to the input lines are, and a reversing device with a switch between the second winding and one of the Input lines is switched, and with a switch control, which are connected between the input lines and is connected to the switch in order to operate it and a controlled reversal of the direction of the motor to effect.

The stator windings can be designed in the manner customary for induction motors. One of the windings is connected to an AC voltage source and received continuously one alternating voltage, while the other at or near zero crossings of the alternating voltage is optionally and periodically connected to the AC voltage source. This excites the engine a very fast reversal of the direction of rotation of the motor »The motor is periodically reversed, e.g. to turn a Alternately drive the agitator of an automatic washing machine.

The motor can be connected to the agitator by a torsion spring be connected, which absorbs the mechanical transients and causes a smooth stirring process.

The circuit arrangement according to the invention can be a relaxation generator having a unijunction transistor which, when it is conductive, controls a gate pulse for a Conducting device is generated which serves as a switch to connect the second stator winding to the voltage input lines to be connected and disconnected from them at certain times.

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An embodiment of the invention is shown below explained with reference to FIGS. 1 to 4. It shows:

1 shows a schematic representation of a washing machine with a circuit arrangement according to the invention,

Fig. 2 is a time diagram of various voltages used for rapid reversal of the direction of rotation of the motor can be applied to the stator windings,

Fig. 3 is a timing diagram of the engine torque and the Synohron speed, from which the speed of the motor direction reversal emerges, and

4 is a schematic circuit diagram of a motor with two stator windings and the associated control circuitry according to the invention.

Fig. 1 shows a washing machine 10 with a container 11, which is carried by a base plate 12. In the loading

the container 11 is arranged a centrifugal drum 13, a has perforated part 14 to allow the passage of washing liquid between the container 11 and the interior of the Centrifugal drum 13 to facilitate.

In addition, in the container 11 or inside the Centrifugal drum 13 an agitator 15 is arranged. The agitator 15 and the drum 13 are driven by a motor 16 which is connected to the agitator 15 by means of a pulley 17, a belt 18, a pulley 19 and a drive shaft 20 is coupled. The drum 13

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and the agitator 15 can be connected for common drive or a coupling (not shown) in FIG can be provided in a known manner around the drum 13 and to drive the drive shaft 20

The agitator 15 can be resiliently coupled to the drive shaft 20, as shown by two torsion springs 21 and 22 is. The springs can be arranged in the upper part of the agitator 15 and with this part of the agitator and the be connected to the upper part of the drive shaft 20. One of the springs 21 and 22 transmits the movement to the agitator 15 when the drive shaft 20 rotates in a first direction and the other of the springs 21 and 22 is transmitting the movement on the agitator when the drive shaft 20 rotates in the other direction. There are others too Types of springs or other resilient drive connections are provided to drive the drive shaft 20 to the agitator 15 to couple and the dynamic torsional load of the motor 1b during its periodic movement or To reduce direction reversal.

The drive motor 16 has a first winding which is connected to an AC voltage source 45 and is in one direction or reciprocating driven by a control circuit 24 operating at or near the Zero crossing of the applied voltage Voltage pulses on a second winding of the motor there. The effect of a properly synchronized voltage pulse from control circuit 24 is to provide a to create negative torque impulse of high strength and short duration. The negative torque pulse is sufficient to increase the inertia of the rotor and the driven load

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overcome and cause an extremely fast reversal of direction of the motor.

The control circuit 2k operates only during the moving interval of a washing period in accordance with a signal applied from a timer 26 through a line 25. The timer 26 can be an electromechanical timer in the usual manner in which a series of switching contacts is actuated in succession by rotating cams. Such timers are known. The timer 26 controls the various operations, including spinning, as indicated by a line 27 to the motor 16. Line 27 may serve to energize an additional high speed winding of motor 16 to achieve a high spin speed during the vent interval of the wash period.

As previously explained, the polarity reversal produces of the voltage applied to an induction motor, a rapid reversal of direction of the motor, if so it is ensured that the polarity reversal occurs near the zero crossing of the voltage. As a result of an energy lag factor During motor operation, the required switching points occur when the current occurs or is close to its maximum vert. Therefore, it is possible for high voltages to destroy the solid-state switch can be generated due to the amount of energy stored in the inductor present in the system is. In order to advantageously carry out a solid-state circuit without the risk of harmful effects from high voltages, can the induction motor with two windings

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are provided that liegssa and on the same axis are polarized in the opposite direction® Eia.® fast © Riefe tiasag reversal the engine can, in a simple »way, daehareia. achieved that one of the stator like sounds in the usual Way is continuously aroused and on the zwei® Wick- =

Zeroing with one passage of the applied Spainmraig ei »voltage pulse is given» Ss was determined _} that a quick motor direction uBikeiir achieved χ $ ®τά.®η kana, if the second winding for the duration i / 2 ₈ 3/2 © d © r 5 / 2 periods of the applied, voltage excited wijrdU bending © types of excitation are shown in Fig. 2 _s w © fe @ i the reversal of direction is initiated at 28 "You play the rotor and the machine load h® ± ά & τ choice of the optimal previously mentioned S ^ reguiigsart & ητ seimelleia. Reversal of direction plays a significant role _s

The excitement beider- Statorwickltmgsa wSlis »© niä liäagerer periods favors the MotorrieiitungstaskeSaX ¹ aicSit uad can lead to blocking and a uazalEssig Ιι © 1ι © κ fleeds. It was also found that the excitation of both windings wäliresä a period equal to an even number of half-periods does not favor reversal, but under certain circumstances such excitation can prevent a proper reversal of direction. This is due to the fact that after the first half cycle of excitation, each subsequent half cycle, which has an opposite polarity, has an opposite effect on the processes which bring about the reversal of direction. It is therefore preferable to zn the motor windings during a period equal to an odd number of half periods. energize, ensuring that the number of

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Half periods that support the first half period, greater than the number of half periods that you counteract, and that the last half-period the has the same polarity as the first.

Within the limits of a household washing machine result, the second stator winding has been energized during 1/2 or 3/2 periods than on proven to be most useful.

Fig, 3 shows the type of torque pulse in the Motor 16 is generated when the windings are adjusted accordingly one of the methods of FIG. 2 can be excited. The torque pulse 29 is ste-ts the previous direction of the Motor rotation is opposite and has a great strength and a short duration. The associated quick reversal of the engine direction is represented by the lower curve in FIG. As shown, the engine can almost immediately reach synchronous speed in the opposite direction, typically within about 100 ms.

Fig. 4 shows the motor 16, the two stator windings and 31 of the type described together with a control circuit 24 for performing a periodic reversal of direction of the motor. The control circuit is economical and is supplied directly via standard AC input lines L1, L2 (source 45) powered, eliminating the need for an additional energy source not applicable. The control circuit 24 has a unijunction transistor 40, which acts as a ripple generator for control the direction reversal impulse is switched, it can

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but also other institutions »e.g. a digital one 60 Hz down counter used for the same purpose will. In addition, a position determination device be provided to initiate the reversal of the motor direction, if they are on the positive half-wave of the input voltage is synchronized.

The circuit shown in FIG. 4 has two stator windings 30, 31 for field excitation of the mator 16. The first winding 30 is connected to the AC input lines L1, L2 are connected and the second winding 31 is connected to a controlled conductive device, ZoB. one controlled silicon rectifier 32 connected in series. This series connection is connected to the input lines L1, L2 connected.

A relaxation generator 33 is provided to control the passage of the rectifier 32. Der'Kippgenerator 33 has a resistor 34, a diode 35 and a capacitor 36 connected in series and connected to the input lines L1, L2 are connected to the line 37 by charging the capacitor 36 through the diode 35 and the Resistor 34 to generate a bias · The DC voltage on line 37 is used to charge through a resistor 3 & a capacitor 39 and to the Emitter of the unijunction transistor 40 the ignition voltage to put on. One base of the unijunction transistor 40 is connected to the conductor 37 via a resistor 4i and receives their DC voltage. The other base is connected to the input line L2 via a resistor 42.

The resistor 42 generates a gate pulse when the unijunction transistor 40 conducts, which is on the control electrode

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of the controlled rectifier 42 is given to this to bring into the conductive state and to connect the second winding 31 to the input lines L1, L2.

The RC time constant of resistor 38 and capacitor 39 determines the ignition period of the unijunction transistor 4o and accordingly the periodic application of the line voltage to the second stator winding 31 · As soon as the rectifier 32 by a pulse on its control electrode 43 is excited, Stx-ctn flows through winding 31 and through rectifier 32 until the magnitude of the current drops to substantially zero. At this time the rectifier switches off and prevents a further flow of current through the winding 31. The winding 31 can thus only be excited during the positive half-cycles of the AC supply voltage.

The periodic ignition of the unijunction transistor 4o, determined by the resistor 3 & and the capacitor 39 is on the voltage zero crossings that precede the positive half-periods of the alternating voltage, synchronized by the supply voltage ripple. Depending on the for the resistor 38 and The values selected for the capacitor 39, the time between the ignition times of the transistor 4o can be several half-periods the AC supply voltage. This synchronization to the zero crossings of the alternating voltage wave is important if a reliable and repeatable reversal of motor direction is to be achieved.

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The line 25 from the aforementioned! ® ± QktT®mGi®h & xi ± a <sh.eiz timer is connected to the prevention element of the liioQ ^ staacIs 38 »of the capacitor 39 and dex> Smitterleitiasig hh of the unijunction transistor 40. Since the emitter of the unijunction transistor feeela "a suitable, not shown Zeitgefoerfsoataki supply line L2 short-circuited where? Dsa ₉ th <ä © sa. Operation of the relaxation generator 33 so. Fo@eK.dea excitation of the rectifier 32 and the S £ ai © sre5 ^f ± © islTO. _I g 31. Thus, the motor 16 can periodically in the desired manner xua other parts of an ashes

Although in the illustrated Ausiiihrungsbeispiol dl © second stator winding 31 only wälireacl the po-sitiirea Halbpesfiodsa the applied voltage energized, is., As di Kus © ^ r® b d. @ Z * Fig. 2, also shows an excitation leads u. ± ® Sgt only during the negative half-periods about voltage to a similarly sehnellea reversal of the motor. The excitation of the waves of positive and negative half-cycles of the applied voltage, as shown by curves c and d in FIG. 2, also leads to a reversal of direction of the motor, although the present control circuit is not designed for this operation.

The illustrated device creates a simple and economical A shaft drive system for a washing machine that works equally well in one direction of rotation as well as swinging. The system also eliminates the need for com-

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22178A7

Plated feedback networks and additional cooling and ventilation devices that were required in the known reversible motor systems in which the mechanical parts are short-lived. The direction reversal is achieved almost instantaneously, so that the motor speed is high enough to prevent overheating and to achieve normal self-ventilation ₄

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Claims (8)

g Munch & i 27.r. a.aößctuer är. Claims (1.! Circuit arrangement for reversing the direction of rotation of a Electric motor in particular a washing machine, characterized through input lines (L1, L2) for eiiae AC voltage that has zero crossings ^ a Rotor, a first and a second stator winding (3O, 3i) t which are inductively coupled to the rotor, wound in opposite directions and connected to the input lines (L1, L2) are, and a reverser with an a Switch (32), which is between the zwei® Wieklraag (31) and one (L2) of the input lines is geesfealt-ct, -sand with a maintenance control * the swissliesa di © EimgaEigsleitung is switched and connected to the switch (32) is to operate this and cause a controlled reversal of direction of the motor (16) « 2. Circuit arrangement according to claim 1 _c , characterized in that the holder control has a Kippgeaarator which is attached to the switch (32). 3 · Circuit arrangement according to claim I ₈ claehircla gekeanzeieh · "net that the switch (32) is a semiconductor switch" which is connected to the second winding (31) and has a control electrode (43) which is connected to the switch control is" 309843/0131 4. Circuit arrangement according to claim 31, characterized in that that the switch control has a unijunction transistor transistor (4o) with an emitter electrode (44) and two base electrodes} a diode (35) and a first capacitor (36) connected in series and connected to the input lines (L2) are connected to bias the transistor (4θ), an RC circuit (3ö, 39) »which are connected in parallel to the first capacitor (36) is to determine the ignition potential of the transistor (4o) as a function of that of the »first capacitor (36) to generate generated DC voltage, and a resistor (42) which is connected to one of the base electrodes and connected to the switch (32) for a pulse to operate the switch when the transistor (4o) conducts. 5 · Circuit arrangement according to claim 4, characterized by a device connected to the RC circuit (30,39), by means of which the generation of the ignition potential for rotating the rotor in one direction is interrupted can· 6. Circuit arrangement according to one of claims 1 to 5 »thereby characterized in that the switch control the switch (32) during at least one .Half period of AC voltage periodically closes to the direction of rotation periodically reverse the rotor 7 · Circuit arrangement according to one of Claims 1 to 6, characterized in that the reversing device has a Has control connection, and that a timer (26) between the input lines (L1, L2) and the control 309843/0131 The end is switched to the beginning of the farmers ’ operations of the reversing facility 8. Circuit arrangement according to any one of claims 1 to 7 »characterized in that the Sehaltersteraeruag with the NuI! Passages of the Wecheelspanxmsig is sated and the switch is operated periodically with a gerimgerea than that of the AC voltage, vm. The direction of rotation of the motor periodically reversed» 309843/0131