Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
  • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
  • H02H7/08—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors
  • H02H7/0833—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors for electric motors with control arrangements
  • H02H7/0844—Fail safe control, e.g. by comparing control signal and controlled current, isolating motor on commutation error
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
  • H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
  • H02P29/02—Providing protection against overload without automatic interruption of supply

Definitions

• the invention relates to a method for determining an operating state when controlling a fan motor, in particular for a fan motor for a motor vehicle.
• the invention further relates to a control circuit for a fan motor, with which an operating state can be determined when the fan motor is controlled.
• Fan motors e.g. for motor vehicles, are usually controlled by a control unit.
• the control unit For stepless control, the control unit generates periodic pulse-width-modulated control signals with which a field-effect power transistor is controlled.
• the field effect power transistor is connected in series with a fan motor that can be connected to the control circuit between two supply voltage potentials.
• the control unit varies a duty cycle of the control signal so that the fan motor is steplessly controlled.
• the pulse duty factor indicates the proportion that the signal level is in a high state during a period of the control signal.
• the high state controls the field effect power transistor so that it is switched through and the entire supply voltage is applied to the fan motor.
• the pulse width modulation signal is low, the field effect power transistor is completely blocked, so that the supply voltage to the fan motor is switched off.
• the frequency of the pulse-width-modulated control signal is usually in a frequency range that cannot lead to audible vibrations in the fan motor or in the control electronics. During assembly and during operation of the fan motor, errors can occur which are usually not easily recognized.
• a method for determining an operating state when controlling a fan motor is provided.
• the fan motor comes with.
• Operated with the help of a switching device the
• Switching device is controlled via a pulse width modulated control signal.
• a pulse duty factor of the control signal specifies a control state of the fan motor, with a voltage potential at the node between the fan motor and switching device or a motor current being measured as a measured variable. Depending on the measured variable and the pulse duty factor, an operating state is determined when the fan motor is activated.
• the method has the advantage that with the help of the voltage potential between the fan motor and the switching device, an exact control is possible with which voltage the ventilation termotor is controlled. With the aid of the duty cycle, it can then be checked whether the voltage potential lies in a target range or whether the voltage potential deviates therefrom.
• the voltage potential can be used as an indicator of the operating state of the fan motor.
• the motor current can also be used as an indicator of the operating state.
• the measured variable is low-pass filtered so that the measured variable is smoothed.
• the low-pass filtered measurement variable essentially only comprises the direct component of the voltage between the fan motor and the switching device or the direct component of the motor current, the direct component being essentially proportional to the pulse duty factor.
• an open load error (open load) is recognized when the voltage potential essentially corresponds to the supply voltage of the fan motor applied to the switching device.
• An open load error means that no current can flow through the fan motor because there is an open circuit in the fan motor and / or an open circuit in the fan motor. This is recognized by the method according to the invention if the supply potential applied to the switching device, which is essentially independent of the pulse duty factor, is essentially measured as the voltage potential.
• the switching device is switched through completely for a certain period of time in order to apply the maximum voltage to the fan motor, so that only oxidized connection points, for example on the brushes of the motors, clean yourself and the fan motor will be able to function again.
• Normal operation is recognized when the voltage potential is essentially proportional to the duty cycle and the measurement voltage is in a defined voltage range in relation to the applied duty cycle. Normal operation is therefore defined by the fact that the voltage potential increases in proportion to the duty cycle and the voltage potential is within a voltage range defined with respect to the respective duty cycle, i.e. between a lower and an upper voltage threshold.
• the defined voltage range can be determined by a previously performed measurement with a defined applied supply voltage with different duty cycles. In this way, the operating points of the respective fan motor can be set at different duty cycles in order to identify voltage deviations from the measured operating points as a fault.
• an overvoltage fault is recognized when the measured voltage potential is above the defined voltage range. Overvoltages can occur, for example, in motor vehicles due to malfunctions in the vehicle electrical system, alternator, battery, etc. occurrence. In order to avoid a resulting defect in the fan motor, it is necessary to recognize overvoltages in good time and take suitable measures to protect the fan motor and the control electronics.
• a blockage or stiffness of the fan motor is recognized when the motor current is outside a defined current range.
• Blockages and stiffness can occur when using fan motors in motor vehicles if Foreign bodies get into the fan driven by the fan motor or if the motor is prevented from rotating or starting due to contamination or corrosion. Blockages and stiffness generally lead to the motor current rising above the current range used in normal operation. In order to prevent the motor from being destroyed in the event of stiffness or blocking, such an operating state must be recognized so that, for example, the motor current can be limited to a harmless level or the fan motor can be switched off.
• the defined current range is determined by a measurement with a defined applied supply voltage under different duty cycles. In this way, the operating points of the respective fan motor can be determined with different duty cycles in order to be able to identify deviations in the motor current from the measured working points as a fault.
• a control circuit for a fan motor for determining an operating state when the fan motor is controlled.
• the circuit comprises a pulse width modulation circuit which controls a switching device with a pulse width modulated signal with a pulse duty factor.
• the switching device is connected to a first supply potential, the fan motor being connectable between a second supply potential and the switching device.
• a measuring circuit is also provided in order to tap a measurement variable at a node between the switching device and the fan motor. The measured variable is checked with the aid of an evaluation circuit and an operating state is determined depending on the measured variable and the pulse duty factor.
• control circuit it is possible to control a fan motor and to determine the operating state of the motor by measuring a measured variable at a voltage node on the fan motor.
• the control circuit can thus determine at any time by measuring the measured variable whether measures have to be taken to protect or activate the motor or whether the motor is in a normal operating state.
• a filter circuit smoothes the measured variable, so that only the direct component of the measured variable is measured by the measuring circuit, the direct component being essentially proportional to the pulse duty factor.
• a matching circuit with a data memory can also be provided in order to carry out a matching of the control circuit.
• the adjustment circuit is connected to the measuring circuit in order to measure a reference variable with a defined applied supply voltage and with a connected fan motor and to store the reference variable as reference values with respect to the respective duty cycle.
• a reference value table look-up table
• the adjustment circuit can preferably store further reference values in the data memory, the adjustment circuit determining the further reference values from the interpolation of the measured reference values. In this way, it is not necessary to measure a corresponding reference value for every possible duty cycle, but one can interpolate further reference values from those already measured, assuming that the measured reference variable is essentially proportional to the duty cycle.
• the evaluation circuit preferably checks the measured variable by comparing the measured variable with the reference values stored in the data memory with respect to the pulse duty factor of the pulse width modulation signal applied and recognizing an operating state depending on the deviation between the measured variable and the reference variable. If a measured variable lies above an upper threshold of the reference value, an overvoltage is detected.
• the measured variable is at the voltage level of the first supply potential, an open load is recognized, ie the fan motor or the feed line to the fan motor have an open circuit. If the measured voltage lies between a lower and an upper threshold, which is determined by the stored reference voltage values, normal operation is recognized. If a measured motor current is above an upper threshold of the reference motor current, stiffness or a blocking of the fan motor is recognized.
• the control circuit preferably has a data interface in order to detect the recognized operating state via a network, e.g. to send a CAN network.
• the measuring circuit can be designed in such a way that a voltage between the fan motor and the switching device is measured and / or a motor current through the fan motor is measured.
• the switching device preferably has a sense FET with which the motor current through the fan motor or through the switching device is measured.
• a sense FET has the advantage that the motor current does not have to be measured via a measuring resistor, which would reduce the supply voltage that is present at the fan motor. Since a proportional current is output to measure the current through the sense FET, a converter circuit is preferably provided which is connected to the sense FET in order to convert the motor current into a proportional voltage. The voltage is then made available to the measuring circuit.
• 1 shows a block diagram of a control circuit according to the invention in accordance with a first embodiment
• 2 shows a filter circuit that can be used in the control circuit according to the invention
• FIG. 3 shows a block diagram for an evaluation circuit according to the invention
• FIG. 4 shows a block diagram of a control circuit according to the invention in accordance with a second embodiment.
• the control circuit 1 shows a control circuit 1 according to the invention in accordance with a first embodiment of the invention.
• the control circuit 1 is used to control a connectable fan motor 2 via the switching device 3.
• the switching device 3 is connected in series with the fan motor 2 and a choke coil 4.
• the inductor 4 serves as a low-pass filter.
• the switching device 3 is preferably designed as a field-effect power transistor, to the gate connection of which a pulse-width-modulated control signal S is applied to control the fan motor.
• the pulse-width-modulated control signal is generated by the control circuit 1.
• a first supply voltage V B t is with a first connection of the inductor 4 and a second connection of the
• Choke coil 4 connected to a first connection of the connectable fan motor 2.
• a second connection of the fan motor tors 2 is connected to a first connection of the field effect power transistor 3.
• a second supply voltage potential V G N D ⁇ preferably a ground potential, is applied to the second connection of the power field effect transistor 3.
• the control signal S is generated by a pulse width modulation circuit 5, which is located in the control circuit 1.
• the pulse width modulation circuit 5 generates the control signal S in accordance with a network interface, e.g. default value received in a CAN network.
• the control signal S is pulse width modulated, i.e. it is periodic and has a cycle length during which a first level is assumed for a certain time and a second level is assumed for the rest of the time of the cycle length.
• the first level is preferably a level with which the switching device 3 can be switched through, preferably a high level.
• the second level blocks the switching device 3 and is preferably a low level.
• the ratio between the length of the first level to the total clock length is defined as the duty cycle Tv.
• the fan motor 2 can be controlled almost infinitely by freely selecting the duty cycle Tv.
• the period of the control signal S is preferably predetermined in accordance with a control frequency which lies above the frequency range audible for the human ear in order to avoid audible unpleasant vibrations in the control electronics or the fan motor 2.
• the drive frequency is preferably approximately 20 kHz.
• a free-wheeling diode 7 is provided so that no voltage peaks are induced in the connecting lines by the fan motor 2 when the switching device 3 is switched off. which derives an occurring voltage peak at the second connection of the fan motor 2 to the first connection of the fan motor 2.
• the choke coil 4 and a suppression electrolytic capacitor 8 are provided.
• the interference suppression electrolytic capacitor 8 is connected with a first connection to the first connection of the fan motor 2 and with a second connection to the second supply voltage potential V G NDr, ie preferably the ground potential.
• the choke coil 4 and the electrolytic capacitor 8 form a low-pass filter.
• the control circuit 1 serves on the one hand to control the fan motor 2 according to a preset value and on the other hand to check the operating state of the fan motor 2.
• the second connection of the fan motor 2 is connected to a low-pass filter circuit 9 located in the control circuit 1.
• the low-pass filter circuit 9 firstly smoothes the voltage signal present at the second connection of the fan motor 2 and transforms it with the aid of a voltage divider into a voltage range which lies in the measuring range of a measuring circuit 10 connected to the filter circuit 9.
• FIG. 2 A possible circuit diagram of such a low-pass filter circuit 9 is shown in FIG. 2.
• the low-pass filter circuit 9 has a first resistor Ri and a second resistor R 2 , which are connected in series and form a voltage divider.
• the measuring voltage V mess is applied across both resistors Ri and R 2 and between the first resistor Ri and the second resistor R 2 the measuring voltage V meSs ' adapted to the required voltage range is tapped.
• the adjusted measuring voltage V mess ' is then applied to a low-pass filter, which is formed by a third resistor R 3 and a capacitor C, so that a direct component is output to the subsequent measuring circuit 10, which is essentially proportional to the pulse duty factor Tv of the control signal S. is.
• the voltage measured in the measuring circuit 10 is essentially proportional to the pulse duty factor Tv of the control signal S and depends on the supply voltage V Bat - V GND applied to the fan motor 2.
• the measuring circuit 10 preferably has an AD converter that digitizes the measured voltage.
• the digitized voltage value is passed on to an evaluation circuit 11 which checks whether the fan motor 2 is in normal operation during operation or whether there is an error.
• the operating state which was determined by the evaluation circuit 11, can be output to a data bus via the data interface 6.
• FIG. 3 shows a block diagram of a possible evaluation circuit 11.
• the evaluation circuit 11 has a data memory 12 in which a table with reference voltage values is stored. According to the pulse duty factor Tv of the control signal S generated by the pulse width modulation circuit 5, a reference voltage value V So is transmitted to a comparator circuit 13.
• the comparator circuit 13 also receives the measurement voltage value digitized by the measurement circuit 10 and compares the two voltage values with one another. If the two voltages differ from each other by more than a threshold amount, or is the
• Measuring voltage value V m ⁇ ss outside a range defined by the reference voltage value it is determined that the fan motor 2 is not in normal operation. If the measurement voltage V m ⁇ S s' is above the upper threshold voltage specified by the reference voltage V So ⁇ , it is determined that the fan motor 2 is operated with an overvoltage will. In this case, an overvoltage fault is recognized, which is passed on to the data interface 6.
• the adjusted measuring voltage V mess ' is essentially independent of the applied duty cycle at the voltage value of the second supply voltage potential V GND , ie ground potential, an open load error is recognized, ie no current flows through the fan motor 2.
• V GND voltage value of the second supply voltage potential
• V GND second supply voltage potential
• an open load error is recognized, ie no current flows through the fan motor 2.
• a defect can consist of brushes and / or collectors being oxidized.
• the evaluation circuit can briefly control the pulse width modulation circuit 5, so that the field effect transistor 3 is completely switched on for a short time, so that the entire supply voltage is present via the fan motor 2. This makes it possible to clean brushes and / or collectors from an oxide layer, so that the fan motor 2 becomes operational again.
• An undervoltage can also be determined with the comparator circuit 13 if the measurement voltage is below the normal operating range specified by the reference voltage value V Soll .
• a matching circuit 14 is provided, which generates the corresponding table before the fan motor 2 is started up.
• a defined supply voltage V Bat is applied to the fan motor 2 and the measurement voltage is measured via the measurement circuit 10 at different duty cycles T v .
• the adjustment circuit 14 it is now possible for the adjustment circuit 14 to write a voltage value into the data memory for each possible duty cycle Tv.
• Tv it is possible for Tv to determine voltage values for some specific duty cycles and other reference voltage values are determined by interpolation between the measured voltage points. This is possible because the adjusted measuring voltage V mess . is essentially proportional to the duty cycle applied.
• FIG. 4 A further embodiment of the invention is shown in FIG.
• the embodiment shown in FIG. 4 is a circuit in which the operating state of the fan motor 2 is determined by the motor current flowing through the fan motor 2.
• a sense FET 20 is provided as the switching device 3 which, in addition to the function of a conventional field effect transistor, also has a current output which provides a current which is proportional to that between the drain through the sense FET 20 and source of the sense FET 20 flowing motor current.
• a measuring resistor can be dispensed with, which otherwise has to be connected in series with the fan motor 2 in order to measure the motor current. Such a measuring resistor reduces the supply voltage applied to the motor and reduces its output.
• the measurement current of the measurement input of the sense FET 20 must be converted into a measurement voltage proportional to it. This is done by an operational amplifier 21, the non-inverting input of which is connected to the measuring current via a first resistor 22.
• the inverting input of the operational amplifier 21 is connected via a second resistor 23 to the source connection of the sense FET 20.
• a control connection of the sense FET 20 is connected to the control signal S, which is provided by the control circuit.
• the source connection of the sense FET 20 is also connected to a ground potential V GND .
• the inverting connection of the operational amplifier 21 is connected to the output of the operational amplifier 21 via a third resistor 24.
• the output of the operational amplifier 21 provides the measurement voltage, which is essentially proportional to the measurement current.
• the voltage at the output of the operational amplifier is made available to the control circuit 1 as the measurement voltage. Since the inputs of the operational amplifier 20 are usually high-resistance, it is necessary to connect the non-inverting input of the operational amplifier 20 to a voltage divider in order to convert the mains current into a voltage.
• the voltage divider 25 has a fourth and a fifth resistor, which are connected in series and to which the first supply voltage potential and the ground potential V GND are applied. Between the fourth and fifth resistors 26, 27, a voltage is tapped which is connected via a sixth resistor 28 to the non-inverting input of the operational amplifier 20.
• the measuring current can flow off via the first resistor 22, the sixth resistor 28 and one of the fourth or fifth resistors 26, 27.
• the voltage at the non-inverting input of the operational amplifier 20 is then proportional to the measurement current, an offset being specified by the voltage divider 25.
• the gain of the operational amplifier is set by the second and fourth resistors 23, 24.
• the measurement voltage can be used to determine whether the fan motor 2 is in normal operation or whether the fan motor 2 is blocked or stiff.
• the measuring current is above the current range valid in normal operation. If the measuring current is increased, the resulting measuring voltage is also increased, so that the control circuit 1 determines that the measuring current is not within a defined range
• control circuit 1 of the second embodiment works the same as the control circuit 1 of the first embodiment. Provision can also be made for the control circuit 1 to have a plurality of inputs for measurement voltages, it being possible on the one hand to provide a measurement voltage between the fan motor 2 and the switching device 20 and also a proportional voltage determined from the measurement current at an input of the control circuit 1. This can also be used to check the plausibility of the "normal operation" operating state.
• the control circuit 1, the switching device 3, the choke coil 4, the freewheeling diode 7 and the interference suppression electrolytic capacitor 8 are preferably of modular construction.
• the module thus formed has two connections for the fan motor 2.
• the pulse width modulation circuit 5 is the
• Measuring circuit 10 the evaluation circuit 11 and the adjustment circuit 14 and the data interface 6 are carried out by appropriate programming in a microcontroller, so that the circuitry is low. It can be provided that the microcontroller is used to control more than one fan motor 2.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Control Of Direct Current Motors (AREA)
• Control Of Electric Motors In General (AREA)

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• 2003
  • 2003-03-26 DE DE10313520A patent/DE10313520A1/de not_active Withdrawn
  • 2003-10-21 BR BRPI0318108A patent/BRPI0318108B1/pt not_active IP Right Cessation
  • 2003-10-21 WO PCT/DE2003/003479 patent/WO2004086601A1/de active Application Filing
  • 2003-10-21 EP EP03779661A patent/EP1611671A1/de not_active Withdrawn
  • 2003-10-21 US US10/550,719 patent/US7595605B2/en not_active Expired - Fee Related

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