Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
  • G01R35/005—Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
  • G01R19/0084—Measuring voltage only

Definitions

• the invention relates to methods and apparatus for measuring terminal voltages in a driver circuit, particularly in driver circuitry for operating an electric motor.
• the present invention relates to calibrating the voltage measurement to measure the terminal voltage in the driver circuit.
• the driver circuit generally comprises two or more than two half-bridge circuits, so-called inverter circuits, which essentially have a series connection of two power semiconductor switches. Between the power semiconductor switches is a center port which is connected to an associated motor port. Depending on the switching state of the power semiconductor switches, the center connection is connected to either a high or a low supply potential.
• a suitable conditioning circuit for example a voltage divider or the like
• a voltmeter for example an analog-to-digital converter
• a control circuit driving the driver circuit For the detection of the terminal voltage certain accuracy requirements apply, which have so far been met by the fact that for the construction of the conditioning circuit components with tight tolerances, eg precision resistors, are used. However, the use of such precision components is complicated because they must be selected accordingly in a selection process.
• a method for calibrating a voltage measurement in particular for measuring a terminal voltage of a driver circuit for an electrical machine, is provided.
• the method comprises the following steps:
• Measuring the voltage at the motor terminal when the second potential is applied in order to obtain a second voltage indication, the second voltage indication being obtained at the applied second defined potential by measuring a voltage conditioned by the conditioning circuit, which is represented by a, in particular linear, mapping the voltage applied to the motor terminal voltage results;
• a correction factor as the slope of a straight line defined by the first and the second voltage specification, it being possible for the correction factor to act on a voltage measured at the motor terminal in order to obtain the real terminal voltage.
• One idea of the above method is to calibrate the conditioned voltage generated, for example, by a voltage divider. For this purpose, first an inverter circuit, which is assigned to the motor terminal, at which the terminal voltage is to be measured, is driven so that the motor terminal is connected to the first defined potential. The resulting terminal voltage is then tapped via the conditioning circuit and a first voltage value is determined, which indicates the conditioned terminal voltage. The terminal voltage is then divided down according to, for example, the mapping of the conditioning circuit, eg, the resistance ratio of the voltage divider.
• each measured terminal voltage can be converted into the actual terminal voltage. This can be done by linearly mapping the measured terminal voltage to the actual terminal voltage. For this purpose, one of the coefficients of the linear relationship determines the slope of the transfer function with which the measured voltage must be corrected in order to obtain the actual terminal voltage.
• the first defined potential can correspond to a first supply potential and the second defined potential to a second supply potential, wherein the supply voltage corresponds to the voltage difference between the first and the second supply potential, wherein the supply voltage is measured to determine the correction factor, wherein the
• Correction factor is determined as the ratio between the supply voltage and the difference between the first supply potential and the second supply potential. According to a further embodiment, from the first and the second
• an offset can be determined, with the offset of a measured voltage at the motor terminal can be acted upon to obtain the real terminal voltage.
• a method for determining a current one
• Terminal voltage provided.
• the method comprises the following steps:
• an apparatus for calibrating a voltage measurement in particular for measuring a terminal voltage of a driver circuit for an electrical machine, is provided.
• the device comprises:
• a conditioning circuit in particular a voltage divider, for modifying a voltage determined by the potential at the terminal connection, so that a conditioned terminal voltage is obtained;
• a measuring unit - to measure the prepared terminal voltage at a motor connection at the first defined potential during the first measurement in order to obtain a first voltage indication
• control unit is designed to determine a correction factor as the slope of a straight line defined by the first and the second voltage specification, wherein a measured voltage can be acted upon by the correction factor at the motor terminal in order to obtain the real terminal voltage.
• an engine system including an electric machine, a controller, and the above apparatus is provided.
• a computer program product including a computer program which, when executed on a data processing unit, executes the above method.
• Figure 1 is a schematic representation of a motor system with a device for measuring the terminal voltages
• FIG. 2 shows a flowchart for illustrating a method for calibrating a voltage measurement for measuring a terminal voltage at a motor terminal of an electric motor.
• the driver circuit 3 in the present embodiment, two inverter circuits 4 in the form of half-bridge circuits, each having a series connection of two power semiconductor switches 5 have.
• the power semiconductor switches 5 are designed, for example, as power MOSFETs, thyristors, IGBTs or the like, depending on the application and the power range.
• the inverter circuits 4 are connected to a high supply potential V H and a low supply potential V L.
• a supply voltage U D c corresponds to the difference between the high supply potential V H and the low supply potential V L.
• two inverter circuits 4 environmentally the first inverter circuit 4 summarizes the first and second power semiconductors terschalter ⁇ ⁇ ⁇ , 5 2 and the second inverter circuit 4 to the third and fourth
• Power semiconductor switch 5 3 , 5 4 The power semiconductor switches 5 are driven by corresponding control signals T1 to T4 by a control unit 6, so that they are either closed (turned on) or opened (not turned on).
• the control of the power semiconductor switch 5 can be done in a known manner, for example by a pulse width modulation, in which the power semiconductor switches 5 are alternately closed and opened at an inverter circuit 4.
• the period of time during which the first power semiconductor switch 5 i, which connects the electric motor 2 to a high supply potential V H indicates the duty cycle determines the electric power provided to the electric motor 2.
• the terminal voltages U1, U2 are tapped and fed to a respective conditioning circuit 8 (here, for example, as a voltage divider).
• the conditioning circuit 8 provides a linear image of the respective terminal voltage, wherein the terminal voltage U1, U2 is acted upon by a constant factor and optionally an offset.
• the respective conditioning circuits 8 provide a conditioned terminal voltage U1_adc, U2_adc.
• the respective conditioning circuits 8 have a series connection of two resistors 9, the processed terminal voltages U1_adc, U2_adc being tapped at an intermediate point between the two resistors 9.
• the division ratio results in a known manner from the wi Resistance values of the resistors 9 of the voltage divider 8.
• the conditioned terminal voltages U 1_adc, U2_adc are made available to a respective analog-to-digital converter input of the control unit 6.
• the control unit 6 includes one or more analog-to-digital converters to the
• the supply voltage UDC is to be detected by means of a further processing circuit 10.
• This can be carried out, for example, with the aid of a further voltage divider 10, so that a conditioned supply voltage UDC_adc is applied to the control unit 6 in order to be detected there by one or more associated analog-to-digital converters 11 for measuring the applied voltages.
• the control unit 6 determines from the division factor of the further voltage divider 10 and from the conditioned supply voltage UDC_adc the supply voltage UDC applied to the driver circuit 3.
• FIG. 2 shows a flow chart for illustrating the method for calibrating the voltage measurement for measuring one of the terminal voltages U1, U2 at the motor terminals A, B.
• step S1 a voltage measurement of the supply voltage UDC is performed.
• step S2 the first line semiconductor switch 5i is closed (and the second line semiconductor switch 5 2 remains open) to apply the high supply potential V H to the first motor terminal A.
• step S3 the resulting processed is in step S3
• Terminal voltage U1_adc (U1 UDC) measured.
• step S4 with the first power semiconductor switch 5i open, the second power semiconductor switch 5 2 is closed by means of the second drive signal T2 in order to apply the low supply potential V L to the first motor terminal A.
• the coefficients (linear factor, ie slope of the straight line: LF, offset: OF) of the linear relationship between U1 and U1_adc can be determined in step S6. The following applies:
• the linear factor corresponds to the correction factor, which indicates a slope of a transfer function between a measured processed voltage and the actual clamping voltage.
• the offset corresponds to the constant component of the transfer function and can possibly be neglected if the conditioning circuit 8 has no offset, as in the exemplary embodiment of the voltage divider.
• the measurement of the voltage for calibration by means of analog-to-digital converters in the control unit 6 is realized.
• the voltage measurement may be made externally, e.g. be determined with suitable voltmeters and therefrom a corresponding correction factor, which is stored in the control unit 6 before the commissioning of the engine system.
• the resistors 9 - directly determine a factor with which the respective measured processed voltage must be applied to determine the corresponding terminal voltages U1, U2.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Control Of Ac Motors In General (AREA)
• Inverter Devices (AREA)
• Control Of Electric Motors In General (AREA)
• Measurement Of Current Or Voltage (AREA)
• Tests Of Circuit Breakers, Generators, And Electric Motors (AREA)

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Applications Claiming Priority (2)

Publications (1)

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Citations (4)

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• 2009
  • 2009-12-08 DE DE200910047608 patent/DE102009047608A1/de not_active Withdrawn
• 2010
  • 2010-11-24 WO PCT/EP2010/068104 patent/WO2011069825A1/de not_active Ceased
  • 2010-11-24 CN CN2010800554657A patent/CN102656473A/zh active Pending
  • 2010-11-24 JP JP2012542443A patent/JP2013513119A/ja active Pending
  • 2010-11-24 EP EP10787720.1A patent/EP2510373B1/de not_active Not-in-force

Patent Citations (4)

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