Abstract:
A submersible motor is provided for a submersible pump, the motor being configured as a single-phase asynchronous motor, which includes a main winding ( 6 ), an auxiliary winding ( 8 ), and a starting device ( 10, 14, 16, 18, 20, 22 ) for controlling the starting procedure of the submersible motor. The starting device ( 10, 14, 16, 20, 22 ) for the control of the current feed of the auxiliary winding ( 8 ) includes at least one electronic switch ( 20 ) in the circuit of the auxiliary winding ( 8 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Section 371 of International Application No. PCT/EP2006/002269, filed Mar. 13, 2006, which was published in the German language on Oct. 5, 2006, under International Publication No. WO 2006/102981 A1 and the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a submersible motor for a submersible pump. 
     Submersible motors are applied with submersible pumps, which are submerged with the motor into a pump sump, in order to deliver a fluid, preferably water, from this sump. These submersible motors are usually driven with alternating voltage from the public electricity mains. For this, the submersible motors are designed as asynchronous motors. Special measures are required for the start or run-up of such an asynchronous motor. Thus, at least one auxiliary winding is provided with single-phase asynchronous motors, which is applied for starting the motor or running it up. The current feed of such an auxiliary winding on running up is effected via a capacitor (capacitor-run-motor with run-up capacitor) or via a resistor (motor with resistor auxiliary phase). These known start methods for an asynchronous motor have certain disadvantages when used as a submersible motor on a submersible pump. 
     Thus, such motors which are started via an auxiliary winding with a resistance, have a low starting moment, which is disadvantageous with submersible motors in submersible pumps. Motors with a run-up capacitor, when used as a submersible motor, have the disadvantage that the electrolyte capacitors may not be arranged in the pump sump with certain applications, so that the starting electronics with the electrolyte capacitor must be arranged outside the pump sump, by which means the wiring effort for the connection of the submersible motor is increased, in particular at least one further electrical lead must be additionally led to the supply leads into the pump sump. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the invention, to create an improved submersible motor for a submersible pump, which provides for a high starting movement and may do away with the arrangement of an electrolyte capacitor for the starting procedure of the motor. 
     The submersible motor for a submersible pump according to the invention is designed as a single-phase asynchronous motor, and comprises a main winding as well as an auxiliary winding for starting or running up the motor. After running up, the auxiliary winding may be disconnected or however may continue to be subjected to current in regular operation of the motor, for example in the manner of a capacitor motor with an operational capacitor. Furthermore, the submersible motor according to the invention comprises a starting device which serves for the control of the starting procedure of the submersible motor. The starting device is formed by an electronic arrangement, which comprises at least one electronic switch in the circuit of the auxiliary winding. The starting device controls the current feed of the auxiliary winding during the starting phase, via this electronic switch. The electronic switch may be actuated by the starting device such that the auxiliary winding is always switched on at exactly the right points in time, in dependence on the angular position of the rotor of the submersible motor and on the phase of the supply voltage. One may thus ensure that the auxiliary winding is always fed with current at the right moment with the right phase, in order to exert a torque impulse on the rotor, i.e., the current feed is matched to the angular position of the electromagnetic field of the rotor, so that the rotor may be accelerated. The starting device may be designed as an individual electronic control device or regulation (closed-loop control) device, or however may be integrated into a superordinate control- or regulation device for operation of the submersible motor, for the actuation of the electronic switch. 
     The targeted controllable current feed of the auxiliary winding via the electronic switch permits a very high starting moment of the motor with a comparatively low starting current. Furthermore, no capacitor is required for the starting procedure of the motor, so that the whole starting device may be arranged directly on the submersible motor, i.e., with the pump sump. In this manner, the necessary wiring to a starting device arranged outside the pump sump becomes superfluous. 
     Preferably, the starting device additionally comprises an electronic switch in the circuit of the main winding for the control of the current feed of the main winding. With the starting procedure, these not only permit the auxiliary winding to be subjected to current in a targeted manner. Moreover, the main winding may also be fed in a targeted manner with current in dependence on the phase of the supply voltage, which is an alternating voltage, and on the rotor position or on the angular position of the rotor magnetic field, in order to produce a torque acting on the rotor and to start the motor. The starting procedure may be further improved by way of this. 
     Preferably, the electronic switch, as is applied in the circuit of the auxiliary winding and/or the circuit of the main winding, is a triac. 
     The starting device is preferably designed in a manner such that for starting the submersible motor, it acquires at least one characteristic value of the induced counter-voltage in the main winding and/or in the auxiliary winding, and controls the current feed of the main- and/or auxiliary winding in dependence on this value. The induced counter-voltage is dependent on the angular position of the rotor or of the rotor magnetic field, so that one may deduce the rotor position from the characteristic values of the induced counter-voltage, and the current feed of the main- and/or auxiliary winding for accelerating the rotor may be controlled in dependence on such a characteristic value, in order to ensure that the current feed is always effected such that a torque acting in the desired rotational direction of the motor acts on the rotor. 
     Further preferably, the starting device is designed such that for starting the submersible motor, it acquires at least one characteristic value of a supply voltage of the submersible motor and controls the current feed of the main- and/or auxiliary winding in dependence of this value. In particular, the starting device acquires the phase course of the supply voltage, so that the current feed of the main- and the auxiliary winding may be effected at the right point in time at the correct phase or the correct phase angle, in order to produce a torque acting on the rotor in the desired direction, in order to accelerate this. 
     According to a preferred embodiment of the invention, the starting device is designed in a manner such that for starting the submersible motor, it switches on the current feed of the auxiliary- or main winding, preferably of the main winding after a detected zero-crossing of the supply voltage, preferably for a certain time interval. Preferably, the auxiliary winding is firstly subjected to current, but it is alternatively also possible to firstly subject the auxiliary winding to current. By way of this procedure, a first magnetization of the rotor takes place on standstill of the submersible motor, in order then to be able to set the rotor into rotation by way of a further current feed of the main- and/or auxiliary winding. This current feed is effected directly after a zero-crossing of the supply voltage, so that it is ensured that the current feed is effected in a certain phase of the supply voltage. The current feed may be effected for a certain time interval and be switched off again after completion of this time interval. It is alternatively possible to switch on the current feed of the main winding in a permanent manner, and to control the further start procedure only via the current feed of the auxiliary winding. 
     Further preferably, the starting device is designed in a manner such that for starting the submersible motor in a second half-period of the supply voltage subsequent to the first switching-on of the current feed to the auxiliary- or the main winding, it switches on the current feed of the main- or the auxiliary winding, preferably of the main winding for a certain time interval. Depending on which of the windings is firstly fed with current, the respective other winding is fed with current in the mentioned second half-period. That is, if according to the preferred embodiment for magnetizing the rotor, it is the main winding which is fed with current first, the auxiliary winding is fed with current in the second half-period. If, according to an alternative embodiment, it is firstly the auxiliary winding which is fed with current, then the main winding is fed with current in the second half-period. Thereby, the second half-period must not directly follow the first half-period in which the first current feed of the main winding is effected, but rather this second half-period may also lie a few periods later. However, the current feed of the auxiliary winding should be effected as close as possible to the first current feed of the main winding with regard to time, such that the magnetization of the rotor due to the current feed of the main winding has not yet decayed. In this manner, a torque is produced on the rotor by way of the current feed of the auxiliary winding and on account of the previously effected magnetization of the rotor by way of the current feed of the main winding. One succeeds in a correctly directed magnetic field acting on the rotor at the right point in time, in order to accelerate this in a desired direction, by way of the fact that the current feed of the auxiliary winding is likewise effected in dependence on the period or the phase of the supply voltage. The current feed of the auxiliary winding is only effected for a certain time interval and afterwards is switched off again, so that it is only a torque impulse which acts on the rotor. 
     The starting device is preferably designed in a manner such that for starting the submersible motor in a third half-period of the supply voltage subsequent to the switching-on of the current feed of the main winding and the auxiliary winding, it determines an angular position of the rotor field in relation to the supply voltage or its phase course, by way of analysis of the induced counter-voltage in the main winding, and on acquiring a predefined angular position relative to the supply voltage, switches on the current feed of the main coil in a subsequent fourth half-period of the supply voltage, for a certain time interval. The third half-period in which this analysis is effected, again does not need to directly follow the first half-period in which the first current feed of the main coil is effected and/or the second half-period in which the current feed of the auxiliary winding is effected, but rather it may also be effected a few half-periods later, wherein the time interval should preferably be selected such that the effect of the preceding torque pulse on the rotor has not yet decayed, i.e., the rotor does not slow down again too much, in order to achieve a further acceleration of the rotor. It is important for the mentioned current feed of the main coil, for this to be effected in a certain angular position of the magnetic field of the rotor matching the phase of the supply voltage, so that a further torque pulse acts on the rotor in the right direction and this is not braked again. That is, the angular position of the rotor is determined such that the main winding is subjected to current with the right phase of the supply voltage at the right moment, in order to further accelerate the rotor. 
     Thereby, preferably the angular position of the rotor field or the magnetic field of the rotor is indirectly acquired via the induced counter-voltage in the main coil. For this, the starting device evaluates characteristic variables of the induced counter-voltage. The current feed of the main winding is effected in the fourth half-period, preferably again only for a certain time interval, thereafter it is switched off again, so that here too, only a torque impulse is produced in the desired direction. 
     The starting device is usefully designed such that the current feed of the auxiliary winding is switched on for a certain time interval after switching on the current feed of the main winding in successive half-period, so that a further torque impulse acts on the rotor. 
     The certain time intervals in which the current feed of the main winding and/or auxiliary winding is switched on according to the preceding description, are preferably in each case equal to or shorter than the duration of a half-period of the supply voltage. In this manner, one ensures that the current feed is always only effected with a rectified phase, i.e., is always effected with the same polarity, so that the magnetic field produced by the coils is always rectified and thus the torque acting on the rotor is always rectified, and the rotor may thus be set into rotation in the desired direction. This length of the time intervals may be effected in a very simple manner by way of the preferred use of triacs as electronic switches, since the triacs after closure automatically open again with the next zero-crossing of the current, and thus interrupt the current feed of the respective main- and/or auxiliary winding. 
     Further preferably, the starting device for determining the angular position, analyses the induced counter-voltage in the main winding at two points in time. This permits the angular position of the rotor field to be determined, alone by way of observing the induced counter-voltage in a winding, specifically in the main winding, so that one may do away with a monitoring or analysis of the induced counter-voltage in the auxiliary winding. The acquisition at two different points in time, permits the temporal course and the gradient of the induced counter-voltage to be determined in an exact manner. Alternatively, one may also acquire the induced counter-voltage in a corresponding manner only in the auxiliary winding. 
     According to a particularly preferred embodiment of the invention, the starting device is designed in a manner such that it switches on the previously described current feed of the main winding in the fourth half-period, when the following three conditions characterizing the predefined angular position of the rotor field relative to the phase angle of the supply voltage are satisfied. The first condition is that the gradient or slope of the counter-voltage induced in the main winding has a reverse polarity to the supply voltage. This observation is effected in the above mentioned third half-period. The second condition is that the counter-voltage induced in the main winding after the subsequent zero-crossing of the supply voltage, i.e., in the fourth half-period, has the same polarity as the supply voltage. The third condition is that in the fourth half-period, the magnitude of the counter-voltage induced in the main winding is smaller than the magnitude of the supply voltage. It is ensured by way of this third condition, that the voltage has the right polarity. By way of the three mentioned conditions, one checks that the magnetic field of the rotor and the phase of the supply voltage, on switching on the current feed of the main winding, are in the desired relation to one another, such that the main winding is subjected to current at the right point in time with the right polarity, in order to produce a torque acting on the rotor in the desired rotational direction. 
     The third and fourth half-period of the supply voltage with the previously described steps are preferably two directly consecutive half-periods. 
     Furthermore, the starting device is preferably designed such that for starting the submersible motor in the case that the angular position of the rotor field required for switching on the current feed of the main coil is not given, it continues the previously described analysis of the induced counter-voltage, until the predefined angular position for switching on the current feed of the main winding is given, and then the current feed of the main winding is switched on. By way of this, it is ensured that the starting device at some time acquires the correct point in time, in which the correct angular position of the rotor field is given, and the switches on the current feed of the main winding in order to produce a torque impulse on the rotor. 
     Furthermore, the starting device is usefully designed in a manner such that the switching-on of the current feed of the main winding on acquiring the predefined angular position and preferably the subsequent switching-on of the current feed of the auxiliary winding, is periodically repeated, until the starting procedure of the submersible motor is completed. In this manner, a torque impulse which acts several times successively on the rotor is produced, which accelerates the rotor. This starting procedure is continued, until the desired rotational speed of the submersible motor is reached. This rotational speed may for example lie between 40 and 70% of the nominal rotation speed. Thus, the starting procedure controlled by the starting device may, e.g., be finished on reaching this rotational speed, and the motor goes over to normal operation. The starting procedure may be finished either after a certain time duration in which normally the desired rotational sped of the motor is achieved, or the actual rotational speed of the motor may be detected via sensors or for example by way of the course of the induced counter-voltage, and the starting procedure may be finished after reaching a certain rotational speed. 
     The starting method according to the invention, which is controlled by the starting device, particularly advantageously proceeds in a manner, such that firstly the main winding is briefly subjected to current, in order to magnetize the rotor which is still at a standstill. Subsequently, at the beginning of a subsequent half-period, i.e., preferably a half-period with the opposite polarity to the supply voltage, the auxiliary winding is briefly subjected to current, in order to produce a first torque impulse which acts on the rotor. The rotor is set into rotation by way of this. This torque impulse may alternatively be also produced in that firstly the magnetization of the rotor is effected by subjecting the auxiliary winding to current and subsequently subjecting the main winding to current, in order to produce the torque impulse. 
     The previously described analysis or observation of the induced counter-voltage is subsequently effected in order to acquire an angular position of the rotor magnetic field which is suitable in relation to the phase course of the supply voltage, at which angular position the main winding is again subjected to current, in order to produce a further torque impulse acting on the rotor in the same direction. Subsequently, in the half-period which follows this, with opposite polarities of the supply voltage, the auxiliary winding is briefly subjected to current, in order to produce a further torque impulse. This current feed of the main winding and the current feed of the auxiliary winding which follows this, is repeated several times, until, as previously described, one reaches a desired rotational speed of the motor, or a certain time duration for the starting procedure has been completed. 
     The electronic switch in the circuit of the main winding further provides the advantage that it may optionally also assume further functions with the control and regulation of the submersible motor. Thus, the electronic switch in the circuit of the main winding may for example be additionally utilized for a phase control, for adapting the submersible motor to different supply voltages, so that for example one and the same submersible motor may be selectively operated at 230 Volts or 110 Volts supply voltage. Thereby, in the known manner, the motor may preferably be designed for the lowest possible supply voltage, and reduces a possibly higher supply voltage by way of the phase control. It is for example further possible to apply the electronic switch as an excess voltage protection for the submersible motor. Furthermore, in combination with a temperature sensor, for example one may also carry out a switching-off of the current feed given an overheating of the submersible motor. The electronic switch cooperates with a control- and regulation device for the operation of the submersible motor, for this additional function, in which control- and regulation device preferably the described starting device is also integrated. A multitude of functions may be realized with a simple construction of the control of the motor in this manner. 
     According to a preferred embodiment of the invention, a capacitor with a further electronic switch, and which is connected in parallel with the electronic switch and preferably arranged in the motor, may be provided in the circuit of the auxiliary winding, wherein the starting device or the control device is designed in a manner such that the auxiliary winding may be subjected to current via the capacitor by way of the further electronic switch after completion of the starting procedure. It is thus possible to start the motor according to the previously described method, and to subsequently operate the motor as a capacitor-run-motor with an operational capacitor. The required capacitance is preferably arranged in the inside of the motor near to the winding. One may possibly also use capacitors without electrolyte as an operational capacitor, so that the arrangement of the operational capacitor in the submersible motor itself is not a problem in many cases of application, in which however the arrangement of an electrolyte capacitor as a starting capacitor in the submersible motor itself is not desired. 
     The starting device is preferably arranged in a housing of the submersible motor on an axial side of the motor which is provided for the connection of a pump, i.e., on the shaft-side winding head of the submersible motor. The connection, in particular a connection plug for the electrical supply lead of the submersible motor, is preferably also provided in this region. One may thus achieve a compact construction of the submersible motor. 
     The control of the starting procedure via the electronic switch in the previously described manner or according to the previously described embodiments, according to a particular embodiment of the invention, permits the influencing of the starting moment on running up the motor. Thus, it is possible to let the motor firstly run up with a low starting moment, and then to increase the starting moment only in the case that the motor should not run up as is wished. In this manner, the torque impacts which occur on running up the motor and which act on the connected pump are reduced. This leads to lower loading of the parts transmitting the torques, so that the wear of these parts and the pump may be reduced on running up. Furthermore, in this manner, one may also reduce the noise formation on running up, which is particularly important with the application of the submersible motor in a house water system. 
     The reduction of the starting moment may be achieved by way of reducing the time intervals in which the auxiliary- and/or the main winding are subjected to current for producing the torque impulses on the rotor. Such a shortening may preferably be effected by way of a later switching-on of the electronic switches for subjecting the main- and auxiliary winding to current. This has the advantage that the automatic switch-off point in time remains uninfluenced, for example with the use of a triac. Alternatively or additionally, the duration of the current feed may also be achieved by way of an earlier switching-off of the electronic switches. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
         FIG. 1  is a schematic circuit diagram of a first embodiment of the starting device of the submersible motor according to the invention, 
         FIG. 2  is a schematic circuit diagram of a second embodiment of the starting device of the submersible motor according to the invention, 
         FIG. 3  is a schematic circuit diagram of a third embodiment of the starting device of the submersible motor according to the invention, 
         FIG. 4  is a diagram in which the voltage course, rotational speed and torque are represented during the starting procedure, 
         FIG. 5  is a sectioned view of a submersible motor according to the invention, and 
         FIG. 6  is a plan view of the submersible motor according to  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  schematically shows the circuit diagram of the submersible motor according to a first embodiment of the invention. A main winding  6  and an auxiliary winding  8  of the submersible motor are connected between the two poles  2  and  4  of the supply voltage, i.e., a neutral lead  2  and the phase  4 . 
     The starting device which controls the current feed of the windings or the coils of the submersible motor in the starting procedure, as an essential element, comprises a controller or a control device  10  which are supplied with current by way of an energy supply  12  via the connection poles  2  and  4  of the submersible motor, wherein the energy supply device  12  prepares the direct voltage required for the control device  10 . The control device  10  is connected to two acquisition devices  14  and  16 , of which the acquisition device  14  acquires the voltage between the poles  2  and  4 , i.e., the supply voltage, and the acquisition device  16  acquires the voltage across the auxiliary winding  8 . The acquisition device  16  thereby acquires the counter-voltage which is induced in the auxiliary winding  8  by the magnetized, rotating rotor. The control device  10  evaluates the course of the supply voltage prevailing between the poles  2  and  4 , as well as the course of the induced counter-voltage prevailing across the auxiliary winding  8 , and by way of this, controls the current feed of the auxiliary winding  8 , as will yet be described in more detail. For this, the control device  10  is connected to an activation unit  18  which activates an electronic switch  20  in the form of a triac, which is situated in the branch or the current circuit of the auxiliary winding  8  between the poles  2  and  4 . 
     The control device, by way of opening and closing the electronic switch  20  by way of actuating the activation unit  18 , may control the current feed of the auxiliary winding  8  in dependence on the voltage courses between the poles  2  and  4  and across the auxiliary winding, which are acquired by the acquisition devices  14  and  16 . Thus the control device  12  may switch on the current feed of the auxiliary winding  8  always exactly when the phase or the phase angle of the supply voltage has a certain relation to the angular position of the rotor magnetic field, so that a torque impulse is produced onto the rotor, in order to set the rotor in motion. 
       FIG. 2  shows a schematic circuit diagram of a submersible motor according to a second embodiment of the invention. The arrangement corresponds in many parts to that arrangement described by way of  FIG. 1 , so that only the differences are discussed hereinafter. The first significant difference to the embodiment according to  FIG. 1  lies in the fact that with the second embodiment, it is not the induced counter-voltage in the auxiliary winding  8  which is acquired by the acquisition device  16 , but the induced counter-voltage in the main winding  6 , and for this, the acquisition device  16  taps the voltage across the main winding  6 . The counter-voltage induced in the main winding  6  may also be used to determine the angular position of the rotor magnetic field. A further difference lies in the fact that an electronic switch  22  is also arranged in the branch or the circuit of the main winding  6  between the poles  2  and  4 . This switch  22  is also designed as a triac. The electronic switch  22  is also activated by the activation unit  18  which receives the control commands from the control device  10 . Additionally, a bypass  24  is provided which may bypass the electronic switch  22 . A switch  26  in the form of relay is arranged in the bypass  24 , which is likewise activated by the control device  10  or a central control device for the motor control. 
     This second embodiment permits the control device  10  to switch on the current feed of the auxiliary winding  8  as well as the current feed of the main winding  6 , for starting the submersible motor, in order to subject the main winding  6  and the auxiliary winding  8  to current in dependence on the acquired angular position of the rotor magnetic field at the right time with the right polarity of the supply voltage, i.e., with the correct phase of the supply voltage, in order to produce torque impulses which act on the rotor for its acceleration. After completion of the starting procedure, i.e., when the submersible motor has reached a certain rotational speed, the electronic switch  20  remains opened, so that the auxiliary winding  8  is not further subjected to current. The switch  26  is then closed, in order to bypass the electronic switch  22  which is then likewise open, and to permanently subject the main winding  6  to current with the supply voltage prevailing between the poles  2  and  4 . 
       FIG. 3  shows a circuit diagram of a submersible motor according to a third embodiment of the invention. This third embodiment corresponds essentially to the embodiment described by way of  FIG. 2 , so that hereinafter only the differences are explained. The third embodiment differs from the embodiment in  FIG. 2  only in that a further bypass  28  is provided, which bypasses the electronic switch  20  in the branch or circuit of the auxiliary winding  8 . A further electronic switch  30 , as well as a capacitor  32 , is arranged in the bypass  28 . 
     With the bypass  28 , the motor may be operated as a capacitor-run-motor with an operating capacitor (capacitor  32 ). For this, the electronic switch  20  is opened by the control device  10  via the activation unit  18 , after the end of the starting procedure. As already described, the electronic switch  22  is also opened, and instead the switch  26  in the bypass  24  is closed, in order to permanently subject the main winding  6  to current. Simultaneously, for normal operation of the motor after completion of the starting procedure, the electronic switch  30  is closed by the control device  10  via the activation unit  18 . In this manner, the auxiliary winding  8  also is permanently subjected to current via the bypass  28 , wherein the capacitor  32  lies as an operational capacitor in the circuit of the auxiliary winding  8 . The operational capacitor  32  may be designed as a capacitor without electrolyte, so that this capacitor  33  may also be applied where no electrolyte capacitor may be arranged in the pump sump. The capacitor  32  is preferably arranged directly in the vicinity of the auxiliary winding  8  in the inside of the motor. 
     The starting procedure or the starting method, as is applied with the embodiment examples according to  FIGS. 2 and 3 , is not described hereinafter in more detail by way of the diagrams in  FIG. 4 . In the upper diagram, the voltage courses of the supply voltage as well as the induced voltage in the main winding  6  in the unit V/100 is represented as a temporal course. The torque course in the unit Nm, as well as the rotor speed in Hz, is represented in the lower part of the diagram. 
     The voltage running with a uniform period represented with an unbroken line is in the phase course of the supply voltage  34  between the poles  2  and  4 . The course  34  of the supply voltage is represented in a dashed manner in the region of the start procedure. In this region, the course of the induced counter-voltage  36  in the main winding  6  is represented by the unbroken line. Furthermore, the control impulses which are delivered by the activation unit  18  to the electronic switches  20  and  22  are represented in the upper part of the diagram. The rotor is idle at the beginning of the method at the point in time zero, and the electronic switch  22  is closed by the switch impulse  38  directly after a zero-crossing of the supply voltage  34 , and the main winding  6  is subjected to current for the first time in this manner. This leads to a first magnetization of the rotor. Since the electronic switches  20 ,  22  are designed as triacs, this current feed of the main coil ends with the next zero-crossing of the supply current. After the next zero-crossing of the supply voltage  34 , a switch impulse  40  is delivered by the control unit  18  in the second half-period on account of the control device  10 , which closes the electronic switch  20 , so that the auxiliary winding  8  is subjected to current. Thus current feed of the auxiliary winding  8  also ends with the next zero-crossing of the supply voltage  24 , with which the electronic switch  20  is automatically opened again. This brief current feed of the auxiliary winding  8  leads to a first torque impulse  42  which is to be recognized in the lower part of the diagram of  FIG. 4 . This first torque impulse  42  acts on the previously magnetized rotor, so that it is set into rotation, as may be recognized from the graph  44  which represents the rotational speed of the rotor. The current feed of the auxiliary winding  8  in the second half-period need not directly follow the half-period in which the main winding  6  was subjected to current for the first time. Rather, this current feed may also be effected a few half-periods later, wherein it must be ensured that the magnetization of the rotor has not yet decayed, and the polarity of the half-period is preferably the opposite of the first half-period, in which the main winding  6  was subjected to current for the first time. 
     An analysis of the counter-voltage  36 , which is induced in the main winding  6  and which is acquired by the acquisition device  16 , is then effected in the subsequent third half-period. If the gradient or the slope of the induced counter-voltage  36  has the opposite polarity to the supply voltage  34 , a first condition for the renewed switching on of the current feed of the main winding  6  is fulfilled. This is the case at point  46 . The second condition for switching-on of current feed of the main winding is that the induced counter-voltage  36  has the same polarity as the supply voltage  34  after the next zero-crossing of the supply voltage  34 , i.e., in the half-period subsequent to this. This is the case at point  48 . At the same time, the magnitude of the induced counter-voltage  36  should be smaller than the magnitude of the supply voltage  34  as a third condition. This is likewise the case at point  48 , so that at this point in time by way of acquiring these three conditions, it is ascertained that the phase course of the rotor magnetic field  50  at this point is in the desired unison with the phase course of the supply voltage  34 , i.e., both are directed in their polarity, such that on subjecting the main coil  6  to the supply voltage  34 , a further torque pulse  52  is produced, which further accelerates the rotor, as is to be recognized on the graph  44 . The further torque pulse  52  is effected by way of producing a switch impulse  54 , which is delivered by the activation unit  18  for closing the electronic switch  22 . 
     A further switch impulse  56  is delivered to the electronic switch  20  in the half-period which follows this, i.e., after the next zero-crossing of the supply voltage  34 , so that the auxiliary winding  8  is subjected to current with the opposite polarity of the supply voltage  34  and thus a further torque impulse  58  is produced on the rotor, so that this is accelerated further. The switch impulses  54  and  56  effect a closure of the electronic switches  22  and  20 , and the switches open automatically again with the next zero-crossing of the current. 
     The described analysis of the induced counter-voltage  36  in relation to the phase course of the supply voltage  34  is subsequently repeated several times, so that whenever the same conditions of the relation of the supply voltage  34  to the phase course of the rotor magnetic field  50  are given, the switch impulses  54  and  56  for closing the electronic switches  22  and  20  are delivered, by which means renewed torque pulses  52  and  58  are delivered. The torque pulses  52  and  58  which are produced by subjecting the main winding  6  and the auxiliary winding  8  to current, are all equally directed, so that the rotor is further accelerated. 
     If the rotor speed has reached a certain level, the starting procedure is completed, and the switch  26  in the circuit of the main winding  6  is closed by way of the permanent switch impulse  60  which sets in at 0.1 seconds in the diagram, so that this main winding is permanently subjected to current. By way of this, then regular torque impulses are produced in the normal known operation of the asynchronous motor, so that the rotor is further accelerated to the constant nominal rotational speed, as may be recognized from the course of the graph  44 . 
       FIGS. 5 and 6  show one example for the constructive construction of the submersible motor according to the invention. The stator  64  is shown in the partly sectioned view in  FIG. 5 , the rotor is not shown and is inserted into the central opening  66  of the stator. A submersible pump (not shown here) to be applied to the submersible motor, connects on the end of the stator  64  which is at the top in  FIG. 5 , and this end is indicated as the shaft-side winding head of the stator  64 . A connection plug extending axially and on which the supply lead for the submersible motor is connected, is formed at this end close to the outer periphery of the stator  64 . A circuit board  70  is also arranged in the region of the shaft-side winding head (see  FIG. 6 ), on which the electronic components of the previously described starting device  10  are arranged. Diametrically opposite to the connection plug  68  the connection terminals  72  for the coil wires of the motor are arranged. This arrangement of the electronics for the starting device or control device  10  of the submersible motor leads to a compact construction of the submersible motor according to the invention. 
     For the application of the previously described starting device as well as the implementation of the described starting method, the windings of the motor are preferably specially adapted. The main winding  6  thereby is preferably not changed with respect to common asynchronous motors with a conventional starting device (capacitor or resistor). The auxiliary winding  8  however is preferably arranged such that the starting current, as well as the heating of the motor, remain within acceptable limits during the starting procedure. It is particularly preferably for the auxiliary winding  8  thereby to be designed such that it comprises 50 to 80% of the windings of the main winding  6 , further preferably between 60 and 75% of the windings of the main winding  6 . 
     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.