Abstract:
The arrangement has a motor ( 16 ) which has an electronic commutator and during operation is supplied from alternating current (AC) mains (L, N) via a rectifier ( 52 ) connected thereto, and a direct current (DC) link ( 22, 58 ) connected to said rectifier ( 52 ) and having a DC voltage (U ZK ) of greater than 100 V. The motor has an arrangement ( 25, 27 ) fed from said alternating current mains (L, N) via a transformer ( 24 ) and for supplying electronic components ( 14, 20, 26 ) of the motor with a DC voltage, and a user interface ( 12 ) provided for transmission of data to or from the motor ( 16 ). Said user interface, with which a current supply ( 24   b ) electrically isolated from the motor ( 16 ) is associated, electrically isolated from the motor ( 16 ).

Description:
FIELD OF THE INVENTION 
     The invention relates to an arrangement with an electronically commutated motor, which during operation is supplied with a DC voltage of over 100 V from an AC main, via a rectifier connected to the mains and via a direct current (DC) link connected to this rectifier. 
     BACKGROUND 
     Since in arrangements of this kind, frequently no transformer is provided between the electronically commutated motor (ECM) and the AC mains, the ECM is not galvanically separated from the AC mains, and this requires special protective measures, in order to prevent danger to the user, in the event of possible insulation damage or the like. 
     SUMMARY OF THE INVENTION 
     An object of the invention, therefore, is to provide a new arrangement of the type mentioned at the beginning. This object is achieved, according to the invention, by means of an arrangement having an electronically commutated motor, which during operation is supplied with a DC voltage of over  100  V from an AC main via a rectifier connected to this main and via a DC link connected to this rectifier, having an arrangement that is supplied with current from this AC main via a transformer and is for supplying electronic elements of the motor with a DC voltage, and having a user interface provided for transmitting information to or from the motor ( 16 ), which interface is galvanically separated from the motor and is associated with a current supply that is galvanically separated from the motor, having a comparator device provided in the user interface, which is supplied with a fluctuating DC voltage that is generated by rectifying a mains-dependent AC voltage, said fluctuating DC voltage being compared in said comparator device with a predetermined signal, in order to generate a pulse-width-modulated (PWM) signal, whose duty ratio is defined by the predetermined signal, and further comprising a device for the galvanically separated transmission of this pulse width modulated signal from the user interface to the motor. The galvanic separation achieves the fact that the user interface is separated from the motor in terms of voltage and is therefore separated from the AC mains, so that any threat to the user or operator is reliably prevented, even in the event of malfunctions in, or damage to, the motor. The pulse width modulated signal can be transmitted to the motor without trouble, e.g. via an isolating transformer, an optical fiber, or an opto-coupler. 
     The invention makes it possible to supply the user interface with an analog signal for the desired speed, to convert this analog signal into digital signals with a signal-dependent duty ratio in a reasonably priced manner inside the user interface, and to transmit these digital signals with the aid of an opto-coupler to the control electronics of the motor, so that they can be further processed there. 
     In a particularly advantageous way, the transformer has an insulated winding chamber in which a separate low-voltage winding is provided, which is used for the galvanically separated current supply of the user interface. By virtue of the fact that this separate low-voltage winding is disposed in an insulated winding chamber, a galvanic separation is produced, which permits a test voltage of 4000 V, for example. It is not necessary to provide a separate isolating transformer for this purpose; rather, the same transformer can also be used for supplying the motor electronics with low voltage. The winding provided for this can be wound in a chamber with the primary winding and separate from the separate low-voltage winding mentioned above. 
     Another advantageous refinement of the invention involves the feature that the output voltage of the separate low voltage winding is adapted to be supplied to the user interface in the form of a rectified fluctuating DC voltage and in the form of a smoothed DC voltage. In a particularly simple manner, the fluctuating DC voltage permits a digitizing of analog signals that are supplied to the user interface, e.g., in order to determine the speed of the motor by means of such an analog signal. 
     Another preferred development of the invention is distinguished by the feature that at least one opto-coupler is provided for the galvanically separated transmission of signals to or from the user interface. The use of an opto-coupler automatically produces a galvanic separation. In this connection, in another development of the invention, the signals are preferably transmitted in digitized form by way of the at least one opto-coupler. In this manner, a reliable signal transmission is obtained, down to the frequency 0. 
     Other details and advantageous improvements of the invention result from the exemplary embodiments, which are described below, are represented in the drawings, and are in no way to be understood as a limitation of the invention. 
    
    
     BRIEF FIGURE DESCRIPTION 
     FIG. 1 is a block circuit diagram explaining the structure of an arrangement according to the invention, 
     FIG. 2 shows details of the arrangement according to FIG. 1, and 
     FIG. 3 is a schematic representation of a power or mains transformer, whose winding body has two winding chambers that are isolated from each other, as well as a preferred arrangement of the windings of the transformer in these winding chambers. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates, by means of a block circuit diagram, an arrangement  8  according to the invention. It includes a power supply  10 , a user interface  12  that is separated from this by means of a symbolically indicated galvanic separation  11 , commutation electronics  14  for the commutation of an electronically commutated motor (ECM)  16  by means of a power output stage  18 , and a current limiting device  20  for limiting the current flowing through the motor  16  to a predetermined maximal value, e.g. at startup of the motor or when it is overloaded. 
     The power supply  10  generates a voltage U ZK  (intermediate circuit voltage) at a DC link  22 . Provided that the mains voltage 220 V is alternating current, U ZK  is an approximately 320 V DC voltage, with which the ECM  16  is supplied directly, i.e. without the interposition of a transformer. Corresponding motor circuits are represented, for example, in EP 0 467 085 A1 HANS &amp; MOINI, corresponding to U.S. Pat. Nos. 5,220,258,  5 , 343 , 129 ,  5 , 589 , 745  and 5,598,073 or DE-UM 9 414 498.2. Due to the relatively high voltage, it is necessary to electrically isolate the user interface  12  completely, relative to the motor  16 , by means of the galvanic separation  11 . 
     By means of a transformer  24 , the power supply  10  generates a low DC voltage of, e.g., 12 V for the commutation electronics  14  and for a Hall generator  26  provided in the motor  16 , whose digital output signal “Hall” (when using a Hall IC) is supplied, as shown, to the commutation electronics  14 , in order to supply thereto information on the instantaneous position of a rotor  42 . This low voltage of 12 V is produced by a first secondary winding  24   a  of the transistor  24 , whose output voltage is rectified by means of a bridge rectifier  25  and is smoothed by means of a capacitor  27 . 
     Transformer  24  also has a second secondary winding  24   b , which is separated from its primary winding  24   c  and the first secondary winding  24   a  by means of a continuous insulation, e.g. due to the fact that the primary winding  24   c  and the first secondary winding  24   a  are wound together in a first chamber of the transformer winding body, while the second secondary winding  24   b  is separately wound in a second winding chamber of the transformer  24  that is insulated from the first chamber. This second secondary winding  24   b  likewise supplies an alternating voltage, e.g. of 12 V, for powering the user interface  12 . 
     At inputs  28  of the user interface  12 , the user can specify the rotation direction of the motor  16  via a signal DR, and this information is transmitted as a signal DIR via an opto-coupler  30  to the commutation control  14 . 
     At inputs  32  of the user interface  12 , the user can preset a desired speed N, e.g. 4300 n, via a signal N SOLL , either in the form of a DC voltage, a PWM signal, or simply in the form of a variable resistance R (FIG.  2 ), i.e. of a passive component (potentiometer), and then via an opto-coupler  34 , a corresponding digital signal NS for the desired speed is supplied to the commutation control  14 . 
     In addition, a signal for the current speed can be taken from the commutation control  14 , e.g. the above-mentioned digital signal Hall. This signal is transmitted in digital form via an opto-coupler  36  to the user interface  12 , is converted there into an analog signal, and is available there at outputs  38 , e.g. for the operation of an instrument that indicates the current speed. 
     As can be readily seen, the user interface  12  is electrically completely insulated, relative to the rest of the arrangement  8 , so that a user is not subjected to any danger whatsoever of an electrical type, when in contact with the user interface  12 . 
     In the embodiment shown, the motor  16  has a single stator winding  40 . Its permanent magnetic rotor is symbolically indicated at  42 . The current through winding  40  flows through a measurement resistor  44 , and the voltage at it is monitored by the current limiting arrangement  20 . If this voltage becomes too high, then the current limiter  20  switches the power output stage  18  off for a short time, via the two AND gates  46 , so that the current through the winding strand  40  correspondingly decreases. 
     At the input of the power supply  10 , there is an Eletcro-Magnetic Interference (EMI) filter  50  having input terminals L, N, across which is applied an AC voltage of, e.g., 220 V. The neutral wire of the mains voltage is designated PE. The task of filter  50  is to contain interference, within the predetermined interference limit values. The mains voltage, filtered by the filter  50 , is rectified directly by means of a full bridge rectifier  52 , smoothed by means of a capacitor  54 , and supplied via the line  22  to the power output stage  18  of the motor  16 . In this way, the output stage  18 , and consequently also the motor winding  40 , are operated with approx. 320 V of DC voltage. Since the commutation electronics  14  can only be operated with low voltage, the transformer  24  is required for this. The negative potential of the DC voltage of 12 V, whose positive potential is present in a line  56 , is connected to the negative potential of the voltage U ZK , as depicted by the common ground connections  58 . Therefore, there is no galvanic separation, with respect to the mains voltage, at the inputs L, N. 
     Since the DC link voltage U ZK  and the DC voltage of 12 V (in the line  56 ) have the same ground potential, the primary winding  24   c  and the first secondary winding  24   a  of the transformer  24  can be wound in the same chamber of a winding body. For safety reasons, though, the supply voltage of the user interface  12  must be galvanically separated from the mains voltage (at the terminals L, N). For the purpose of galvanic separation, the second secondary winding  24   b  is therefore preferably wound in a separate chamber of the transformer  24 . As a result of this structure of the transformer  24 , no other isolation measures are needed, and reasonably-priced two-chamber winding bodies can be used for the transformer  24 , by means of which its costs are kept within limits. 
     Numeral  62  designates a mains monitor, which monitors the voltage U ZK  in the line  22  and the DC voltage (e.g. +12 V) in the line  56 . The reason for this is as follows: when switching on the arrangement  8 , i.e. when supplying mains voltage to the terminals L and N, the voltage U ZK  (in the line  22 ) increases very rapidly, while it takes longer to build up the DC voltage in the line  56 , which supplies the Hall generator  26 , the commutation control  14 , and the current limiter  20  with energy. 
     For this reason, without the mains monitor  62 , the switching state of the output stage  18  would not be unambiguously defined. Since the output stage  18  is preferably a full bridge circuit, this unclearly defined switching state could lead to a short circuit in this bridge. 
     An analogous problem arises when the arrangement  8  is switched off from the utility main. Here, too, the DC voltage in the line  56  goes to zero significantly faster than the voltage U ZK  in the line  22 , because when the switch-off occurs, the rotor  42  continues to rotate and supplies energy back to the DC link, i.e. the line  22 , until the rotor comes to a stop. Therefore, U ZK  decreases in proportion to the speed of the motor  16  and here, too, without the mains monitor, it can lead to a short circuit in the full bridge circuit (in the output stage  18 ) or to an overvoltage at the output stage  18 , which likewise jeopardizes this output stage. 
     The mains monitor  62  therefore detects the voltage U ZK  and the voltage in the line  56 . If the latter becomes too low, and U ZK  lies above a predetermined value, the mains monitor supplies the line  56  with a DC voltage, e.g. from a battery provided for this (not shown), or from the line  22  by means of a voltage regulator (not shown). 
     In this manner, the commutation of the motor  16  is assured, directly from switch-on, by the commutation control  14 , as well as from switch-off until the rotor  42  comes to a stop. The current limiter  20  also becomes effective in this manner, starting directly from switch-on, and thus prevents any overloading of output stage  18 , and destruction thereof. 
     FIG. 2 shows the structure of the user interface  12  in detail. The primary winding  24   c  of the transformer  24  is connected via the EMI filter  50  (terminals L, N) to an AC mains (not shown). 
     Line  56  (+12 V) is powered by the first secondary winding  24   a , which is wound together with the primary winding  24   c  in a chamber  68  (FIG. 3) of an isolating winding body  72  of the transformer  24 , while the second secondary winding  24   b  is wound in a second chamber  70  of the winding body  27  separate from this. The dividing line, between the two halves of the transformer core, is designated  24   d . 
     The first secondary winding  24   a  also powers a line  70 ′, on which a Zener diode  72 ′ generates a voltage of + 5  V, measured with respect to ground  58 . 
     The output voltage of the second secondary winding  24   b  is supplied to a full bridge rectifier  74  in the user interface  12 . Its positive output is designated  76 , and its negative output is designated  78 . The latter is also designated 0 V, since it is not connected to the ground  58  of the motor  16 , but represents an internal potential of the user interface  12 . 
     Across the outputs  76  and  78 , there is a pulsating DC voltage with a frequency of 100 Hz, which serves, in the user interface  12 , to digitize a signal N SOLL  fed to the input  32  for the desired speed of the motor  16 . (In this instance, this signal can be supplied as a DC voltage with a voltage range of e.g. 0 to 10 V, or can be supplied as a pulse width modulated signal (PWM signal), or simply by virtue of the fact that a variable resistor R (FIG.  2 ), e.g. a potentiometer, is connected to the input  32 . The latter has the particular advantage that the user does not have to supply any active, i.e. energy-supplying, set point or target value signal. The pulsating DC voltage between the outputs  76  and  78  is filtered by a small capacitor  77  (e.g. 100 Nf) in order to filter out high-frequency components from the pulsating DC voltage. 
     Starting from the output  76 , a diode  80  and a resistor  82  lead to a line  84 , on which a Zener diode  86  and a smoothing capacitor  88  generate a smoothed DC voltage of +10 V, which is used to supply current to the LEDs  30 ′,  34 ′ of the two opto-couplers  30 ,  34  and to a comparator  90 . 
     In this instance, the secondary winding  24   b  thus functions like an isolating transformer, which galvanically separates the user interface  12  from the AC mains and from the motor  16 . The test voltage for the isolation of the winding  24   b , relative to the other windings, can be 4000 V, for example. 
     The pulsating DC voltage (100 Hz) across the connections  76 ,  78  is fed via a voltage divider  94 ,  96  to the positive input  98  of the comparator  90 . The negative input  100  of this comparator is limited to a predetermined maximal voltage via a Zener diode  102  and a resistor  104 . A capacitor  106  and the series circuit of two resistors  108 ,  110  are disposed parallel to the Zener diode  102 , between the input  100  and the line  78  (0 V) and the connecting point  112  of these resistors is connected to one of the inputs  32 , which can be supplied with a signal value for the desired target speed N SOLL , e.g. in the form of a DC voltage between 0 and 10 V. If the target speed is supplied in the form of a PWM signal, this is smoothed by means of the resistor  108  and the capacitor  106 . 
     The pulsating DC voltage at the positive input  98  of the comparator  90  can be thought of approximately as a delta voltage. If the voltage is low between the inputs  32 , then the potential of the negative input  100  is low, and the output  118  of the comparator  90  is therefore high for only a short time during each period of the pulsating DC voltage (100 Hz corresponds to 10 ms), e.g. for 1 ms, and then is low for 9 ms, i.e. a low pulse duty ratio is produced at the output  118 . 
     If the voltage between the inputs  32  is high, then the output  118  is correspondingly high during each period of the pulsating DC voltage, e.g. is high for 6 ms and low for 4 ms, i.e. the duty ratio at the output  118  increases when the DC voltage signal at the input  32  increases. 
     The output  118  of the comparator  90  is connected to the line  78  via the series circuit of two resistors  120 ,  122 . Their connecting point  124  is connected to the cathode of the LED  34 , in the opto-coupler  34 . 
     The output  118  is likewise connected via the series circuit of two resistors  126 ,  128  to the line  84  (+10 V). Their connecting point  130  is connected to the anode of the LED  34 ′. 
     Therefore, as long as the output  118  of the comparator  90  is high, the LED  34 ′ receives an operating voltage, illuminates, and therefore transmits the digital signal NS to the output  134  of the opto-coupler  34 . However, if the output  118  is low, then the LED  34 , receives no voltage and therefore does not illuminate. As a result, a corresponding signal NS is obtained at the output  134 . 
     For presetting the rotation direction for the motor  16 , a resistor  140  can be connected between the inputs  28  of the user interface  12 , by means of which the LED  30 ′ in the opto-coupler  30  illuminates, the signal DIR at the output  142  of the opto-coupler  30  becomes low, and the motor  16  is switched over to a rotation counter to its preferred direction. If the resistor  140  is omitted, then the LED  30 ′ is without current and the signal DIR becomes high, by means of which the motor  16  is switched over to its preferred direction. 
     The output  142  is connected via a resistor  146  to the line  70  (+5 V). 
     The digital signals DIR and NS are galvanically separated from the user interface  12  by means of the opto-couplers  34  and  30 , respectively, so that a galvanic separation exists here as well. 
     Naturally, a large number of alterations and modifications are possible within the scope of the current invention. In lieu of the second secondary winding  24   b , a separate isolation transformer, for example, could be provided with a corresponding winding, but the embodiment shown is preferable, due to its highly favorable cost.