CN100563090C

CN100563090C - Phase current detector

Info

Publication number: CN100563090C
Application number: CNB2006101467115A
Authority: CN
Inventors: 前田敏行; 谷口智勇
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2001-09-25
Filing date: 2002-09-25
Publication date: 2009-11-25
Anticipated expiration: 2022-09-25
Also published as: CN100546164C; CN101494426B; CN1953313A; CN1953312A; CN100517939C; CN101567639B; CN101567639A; CN100468940C; CN1972100A; CN1953314A; CN101552571B; CN101552571A; CN101494426A; CN1972101A; CN100481702C

Abstract

The invention provides a kind of phase current detector.Between the lead-out terminal of the rectification circuit that is used for input ac power (1) (2), connect first capacitor (2a), first capacitor (2a) and three-phase inverter (3) are connected in parallel, and the output of three-phase inverter (3) is offered motor (4).Then, at the input side of three-phase inverter (3) second capacitor (3a) that is connected in parallel, between first capacitor (2a) and second capacitor (3a), connect current detector (5), from current detector (5) the 3rd capacitor and first capacitor (2a) only are connected in parallel at mains side, in the scope that the surge voltage that power device can not cause owing to switch is damaged, get the capacitance settings of second capacitor (3a) minimum, but suppressed ringing in addition, and can be at a high speed and the done with high accuracy electric current be taken into.

Description

Phase current detector

The application is that the original bill application number is 02802758.2 application for a patent for invention (international application no: PCT/JP02/09901, the applying date: on September 25th, 2002, denomination of invention: dividing an application phase current detector).

Technical field

The present invention relates to a kind of phase current detector, this phase current detector is offering the output from the PWM inverter in the motor drive of motor and drive motor, detects the phase current of motor according to the electric current and the additional polar plot of DC link.

Background technology

In the past, driving by inverter in the motor drive of motor,, a kind of device that makes the output pulse be deformed into the output that can measure had been proposed as the device that is used to detect motor phase current.

When adopting said structure, produce following unfavorable condition, that is: the amperometric determination error that causes by ring, by the wave distortion that the prolongation of pulse output time causes, operating range dwindle the generation of extraordinary noise etc.

Particularly, because any parsing scheme to ring is not proposed, thereby have following unfavorable condition, that is: be difficult to reduce ring, can not carry out the high speed reaction, perhaps can not improve the mensuration precision.

And, though consider and to use parallel resistance to detect the pulse current that flows through DC link, but be difficult to reduce The noise and improve the mensuration precision, and because the crest voltage that causes by the inductance of parallel resistance, existence can not be carried out the unfavorable condition of current detecting to the pulse beyond the long pulse.Therefore, use parallel resistance to detect phase current and also do not reach practicability.

Summary of the invention

The present invention makes in view of the above problems, the purpose of this invention is to provide a kind of can suppressed ringing and with at a high speed and the phase current detector that is taken into of done with high accuracy electric current.

In addition, another object of the present invention provides a kind of phase current detector that can use parallel resistance with the high Precision Detection phase current.

Phase current detector is according to a first aspect of the invention offering the output from the PWM inverter in the motor drive of motor and drive motor, detects the phase current of motor according to the electric current and the additional polar plot of DC link; It is characterized in that, in the scope that the surge voltage that power device can not cause owing to switch is damaged, must be as far as possible little the capacitance settings of the by-pass capacitor of the power device side that is arranged on the current detector on the DC link.

Phase current detector is according to a second aspect of the invention offering the output from the PWM inverter in the motor drive of motor and drive motor, detects the phase current of motor according to the electric current and the additional polar plot of DC link; It is characterized in that, the capacitance settings of the by-pass capacitor of the power device side that is arranged on the current detector on the DC link is become to make by the electric current on the combined capacity of a pair of capacitor of mains side and the current detector that the resonance phenomena that wiring inductance produced between these capacitors causes below the detectable minimum current of current detector.

Phase current detector is according to a third aspect of the invention we offering the output from the PWM inverter in the motor drive of motor and drive motor, detects the phase current of motor according to the electric current and the additional polar plot of DC link; It is characterized in that the structure of this phase current detector is for directly offering power device to electric current from the by-pass capacitor of mains side by the current detector on the DC link.

Phase current detector is according to a forth aspect of the invention offering the output from the PWM inverter in the motor drive of motor and drive motor, detects the phase current of motor according to the electric current and the additional polar plot of DC link; It is characterized in that, low pass filter is set in current detector, and the cut-off frequency of this low pass filter is set at can be in the evaluated error scope, to the frequency that is fully suppressed by wiring from the by-pass capacitor of mains side to the wiring of power device, from the power device to the motor and ringing frequency component that motor produced.

According to a fifth aspect of the invention phase current detector adopts the low pass filter that comprises the switching part that is used to switch cut-off frequency as above-mentioned low pass filter.

Phase current detector is according to a sixth aspect of the invention offering the output from the PWM inverter in the motor drive of motor and drive motor, detects the phase current of motor according to the electric current and the additional polar plot of DC link; It is characterized in that, in current detector, be provided with and have the filter that can on the minimum voltage vector length of regulation, detect the response speed of electric current, and the line length of setting from the inverter to the motor, so that use this filter, making by the by-pass capacitor from mains side is more than the quenchable frequency to the wiring of power device, the wiring from the power device to the motor and the ring that motor produced.

Phase current detector according to a seventh aspect of the invention adopts the filter of the low pass filter that comprises the through-rate of utilizing amplifier as above-mentioned filter.

According to an eighth aspect of the invention phase current detector adopts to have ringing frequency and maximum output voltage is multiplied each other the amplifier of the through-rate below the value that is obtained as above-mentioned amplifier.

Phase current detector according to a ninth aspect of the invention adopts the amplifier by operational amplifier constitutes and frequency band is comprised by the amplifier conduct of feedback capacity restriction in current detector.

Phase current detector is according to the tenth aspect of the invention offering the output from the PWM inverter in the motor drive of motor and drive motor, detects the phase current of motor according to the electric current and the additional polar plot of DC link; It is characterized in that, with current detector the filter that is made of the LC series resonant circuit is set in parallel, and makes its resonance frequency with consistent by wiring from the by-pass capacitor of mains side to the wiring of power device, from the power device to the motor and ringing frequency that motor produced.

Phase current detector is according to an eleventh aspect of the invention offering the output from the PWM inverter in the motor drive of motor and drive motor, detects the phase current of motor according to the electric current and the additional polar plot of DC link; It is characterized in that, this phase current detector comprises the decision parts, at least one side in rising edge time of delay, trailing edge time of delay and the current waveform of these decision parts pair electric current that flows through DC link at least corresponding with the instruction of issuing inverter measures, and according to measurement result, at least one side in timing of decision current detecting and the minimum voltage vector length.

Phase current detector according to a twelfth aspect of the invention adopts following decision parts as above-mentioned decision parts, these decision parts are when starting, flow through at direct current under the state of motor, at least one side in rising edge time of delay, trailing edge time of delay and the current waveform of the electric current that flows through DC link at least corresponding with the instruction of issuing inverter is measured.

Phase current detector according to a thirteenth aspect of the invention adopts the motor drive that uses the triangular wave manner of comparison to carry out the generation of PWM ripple as above-mentioned motor drive, and adopt following decision parts as above-mentioned decision parts, at least one side in rising edge time of delay, trailing edge time of delay and the current waveform of these decision parts pair electric current that flows through DC link at least corresponding with the instruction of issuing inverter measures, and is used for the amperometric determination that phase current detects at rising edge, the trailing edge inclined side separately of triangular wave.

Phase current detector according to a fourteenth aspect of the invention adopts following decision parts as above-mentioned decision parts, these decision parts are not used for the amperometric determination that phase current detects, and at least one side in rising edge time of delay, trailing edge time of delay and the current waveform of the electric current that flows through DC link at least corresponding with the instruction of issuing inverter is measured.

Phase current detector according to a fifteenth aspect of the invention is used to drive the motor of hermetic type compressor as above-mentioned motor.

Phase current detector is according to a sixteenth aspect of the invention offering the output from the PWM inverter in the motor drive of motor and drive motor, uses parallel resistance that the electric current that flows through DC link is detected; It is characterized in that this phase current detector has first filter, this first filter is offset the error that is caused by the subsidiary inductive component of parallel resistance.

Phase current detector according to a seventeenth aspect of the invention adopts following first filter as above-mentioned first filter, and this first filter has limit at the frequency place lower than the upper limit of the desired frequency characteristic of current detection circuit.

Phase current detector according to an eighteenth aspect of the invention adopts following first filter as above-mentioned first filter, and this first filter includes and the identical limit of the zero frequency that inductive component produced of being attached by parallel resistance and parallel resistance.

Phase current detector according to a nineteenth aspect of the invention also comprises second filter, and this second filter is eliminated the useless oscillating component of the electric current that flows through parallel resistance.

According to a twentieth aspect of the invention phase current detector adopt by passive component constitute and with the direct-connected filter of parallel resistance as above-mentioned first or second filter.

Phase current detector is according to a twenty-first aspect of the invention offering the output from the PWM inverter in the motor drive of motor and drive motor, uses parallel resistance that the electric current that flows through DC link is detected; It is characterized in that this phase current detector has noise elimination apparatus, this noise elimination apparatus is eliminated the noise that is caused by the magnetic flux from parallel resistance and DC link generation.

Phase current detector is according to a twenty-second aspect of the invention offering the output from the PWM inverter in the motor drive of motor and drive motor, uses parallel resistance that the electric current that flows through DC link is detected; It is characterized in that this phase current detector is equipped with circuit element, so that be not subjected to the The noise that causes by the magnetic flux that produces from parallel resistance and DC link.

Phase current detector according to a twenty-third aspect of the invention is mounted to plane parallel with the magnetic flux that is produced by parallel resistance and DC link to circuit element.

Phase current detector according to a twenty-fourth aspect of the invention is used for handle and offers the motor drive of motor and drive motor from the output of PWM inverter, and comprises: for detecting the parallel resistance that motor current inserts DC link; Current detection circuit; To detect the microcomputer of electric current output as input; It is characterized in that, the signal ground of current detection circuit and microcomputer ground wire are connected a side of parallel resistance.

Phase current detector according to the twenty-fifth aspect of the invention is used for handle and offers the motor drive of motor and drive motor from the output of PWM inverter, and comprises: for detecting the parallel resistance that motor current inserts DC link; Current detection circuit; To detect the microcomputer of electric current output as input; It is characterized in that, common mode choke is inserted between current detecting output and the microcomputer ground wire.

Phase current detector according to a first aspect of the invention is when being used for the motor drive that offers motor and drive motor from the output of PWM inverter, when detecting the phase current of motor according to the electric current of DC link and additional polar plot, in the scope that the surge voltage that power device can not cause owing to switch is damaged, must be as far as possible little the capacitance settings of the by-pass capacitor of the power device side that is arranged on the current detector on the DC link, thereby can not make the electric current ring that causes by resonance flow to current detector, can improve current detection accuracy.

Phase current detector according to a second aspect of the invention is when being used for the motor drive that offers motor and drive motor from the output of PWM inverter, when detecting the phase current of motor according to the electric current of DC link and additional polar plot, it is below the detectable minimum current of current detector that the capacitance settings of the by-pass capacitor of the power device side that is arranged on the current detector on the DC link is become the electric current make by on the combined capacity of a pair of capacitor of mains side and the current detector that the resonance phenomena that wiring inductance produced between these capacitors causes, thereby can significantly reduce evaluated error, can improve the amperometric determination precision.

Phase current detector according to a third aspect of the invention we is when being used for the motor drive that offers motor and drive motor from the output of PWM inverter, when detecting the phase current of motor according to the electric current of DC link and additional polar plot, electric current is directly offered power device from the by-pass capacitor of mains side by the current detector on the DC link, thereby can be suppressed to the influence of resonance current and be roughly 0, can improve the amperometric determination precision.

Phase current detector according to a forth aspect of the invention is when being used for the motor drive that offers motor and drive motor from the output of PWM inverter, when detecting the phase current of motor according to the electric current of DC link and additional polar plot, low pass filter is set in current detector, and the cut-off frequency of this low pass filter is set at can be in the evaluated error scope, to by wiring from the by-pass capacitor of mains side to power device, the frequency that wiring from the power device to the motor and the ringing frequency component that motor produced fully suppress, thereby can be in the evaluated error scope, the ringing frequency component is fully suppressed, can improve the amperometric determination precision.

According to a fifth aspect of the invention phase current detector adopts the low pass filter that comprises the switching part that is used to switch cut-off frequency as above-mentioned low pass filter, thereby except variation that can the flexible adaptation length of arrangement wire etc., can also reach and same according to a forth aspect of the invention effect.

Phase current detector is when being used for the motor drive that offers motor and drive motor from the output of PWM inverter according to a sixth aspect of the invention, when detecting the phase current of motor according to the electric current of DC link and additional polar plot, in current detector, be provided with and have the filter that can on the minimum voltage vector length of regulation, detect the response speed of electric current, and the line length of setting from the inverter to the motor, so that use this filter, make by wiring from the by-pass capacitor of mains side to power device, wiring from the power device to the motor and the ring that motor produced are more than the quenchable frequency, thereby can fully suppress the ringing frequency component, can improve the amperometric determination precision.

Phase current detector according to a seventh aspect of the invention adopts the filter of the low pass filter that comprises the through-rate of utilizing amplifier as above-mentioned filter, thereby can reach and same according to a sixth aspect of the invention effect.

According to an eighth aspect of the invention phase current detector adopts to have ringing frequency and maximum output voltage is multiplied each other the amplifier of the through-rate below the value that is obtained as above-mentioned amplifier, thereby can reach and same according to a seventh aspect of the invention effect.

Phase current detector according to a ninth aspect of the invention adopts the amplifier by operational amplifier constitutes and frequency band is comprised by the amplifier conduct of feedback capacity restriction in current detector, thereby can significantly reduce overshoot and Xia Chong, can reach and any one same effect to the eight aspect according to a first aspect of the invention.

Phase current detector according to the tenth aspect of the invention is when being used for the motor drive that offers motor and drive motor from the output of PWM inverter, when detecting the phase current of motor according to the electric current of DC link and additional polar plot, with current detector the filter that is made of the LC series resonant circuit is set in parallel, and make its resonance frequency with by wiring from the by-pass capacitor of mains side to power device, wiring from the power device to the motor and the ringing frequency unanimity that motor produced, thereby can reduce the influence of ring, can improve current detection accuracy.

Phase current detector according to an eleventh aspect of the invention is when being used for the motor drive that offers motor and drive motor from the output of PWM inverter, when detecting the phase current of motor according to the electric current of DC link and additional polar plot, this phase current detector comprises the decision parts, the rising edge time of delay of these decision parts pair electric current of at least flowing through DC link corresponding with the instruction of issuing inverter, at least one side in trailing edge time of delay and the current waveform measures, and according to measurement result, at least one side in timing of decision current detecting and the minimum voltage vector length, thereby can reduce the influence of delay of causing by device etc., and can improve current detection accuracy.

Phase current detector according to a twelfth aspect of the invention adopts following decision parts as above-mentioned decision parts, these decision parts are when starting, flow at direct current under the state of motor, at least one side in rising edge time of delay, trailing edge time of delay and the current waveform of the electric current that flows through DC link at least corresponding with the instruction of issuing inverter is measured, thereby can current value do not change and the also indeclinable state of PWM width under measure time of delay, and then can improve current detection accuracy.

Phase current detector according to a thirteenth aspect of the invention adopts the motor drive that uses the triangular wave manner of comparison to carry out the generation of PWM ripple as above-mentioned motor drive, and adopt following decision parts as above-mentioned decision parts, the rising edge time of delay of these decision parts pair electric current of at least flowing through DC link corresponding with the instruction of issuing inverter, at least one side in trailing edge time of delay and the current waveform measures, and at the rising edge of triangular wave, trailing edge inclined side separately is used for the amperometric determination that phase current detects, thereby always can be when measuring time of delay, carry out phase current and measure, can improve current detection accuracy.

Phase current detector according to a fourteenth aspect of the invention adopts following decision parts as above-mentioned decision parts, these decision parts are not used for the amperometric determination that phase current detects, at least one side in rising edge time of delay, trailing edge time of delay and the current waveform of the electric current that flows through DC link at least corresponding with the instruction of issuing inverter is measured, even thereby when adopting no symmetric mode, also can suitably stop the phase current detection and carry out mensuration time of delay, can improve current detection accuracy.

Phase current detector according to a fifteenth aspect of the invention is used to drive the motor of hermetic type compressor as above-mentioned motor, thereby when driving hermetic type compressor, can reach and any one same effect to the 14 aspect according to a first aspect of the invention.

Phase current detector according to a sixteenth aspect of the invention is when being used for the motor drive that offers motor and drive motor from the output of PWM inverter, when using parallel resistance that the electric current that flows through DC link is detected, use first filter can offset the error that causes by the subsidiary inductive component of parallel resistance, and then can improve the phase current accuracy of detection.

Phase current detector according to a seventeenth aspect of the invention adopts following filter as above-mentioned first filter, this filter has limit at the frequency place lower than the upper limit of the desired frequency characteristic of current detection circuit, thereby can in wide region, reach falt characteristic, and then can improve the phase current accuracy of detection.

Phase current detector according to an eighteenth aspect of the invention adopts following filter as above-mentioned first filter, this filter includes and the identical limit of the zero frequency that inductive component produced of being attached by parallel resistance and parallel resistance, thereby can in wide region, reach falt characteristic, and then can improve the phase current accuracy of detection.

Phase current detector according to a nineteenth aspect of the invention also comprises second filter, this second filter is eliminated the useless oscillating component of the electric current that flows through parallel resistance, thereby except the influence that can get rid of useless oscillating component, also can reach and any one same effect to the tenth eight aspect according to a sixteenth aspect of the invention.

According to a twentieth aspect of the invention phase current detector adopt by passive component constitute and with the direct-connected filter of parallel resistance as above-mentioned first or second filter, thereby can adopt and be difficult to produce the inexpensive construction that causes error by non-linear, reach and any one same effect to the 19 aspect according to a sixteenth aspect of the invention.

Phase current detector according to a twenty-first aspect of the invention is when being used for the motor drive that offers motor and drive motor from the output of PWM inverter, when using parallel resistance that the electric current that flows through DC link is detected, use noise elimination apparatus, the noise that causes by magnetic flux can be eliminated, the phase current accuracy of detection can be improved from parallel resistance and DC link generation.

Phase current detector according to a twenty-second aspect of the invention is when being used for the motor drive that offers motor and drive motor from the output of PWM inverter, when using parallel resistance that the electric current that flows through DC link is detected, by circuit element is installed, the The noise that causes by the magnetic flux that produces from parallel resistance and DC link can be subjected to, the phase current accuracy of detection can be improved.

Phase current detector according to a twenty-third aspect of the invention is mounted to circuit element and the magnetic flux plane parallel that produces from parallel resistance and DC link, thereby can reach and same according to a twenty-second aspect of the invention effect.

Phase current detector according to a twenty-fourth aspect of the invention is when being used for the motor drive that offers motor and drive motor from the output of PWM inverter, use is inserted parallel resistance in the DC link for detecting motor current, current detection circuit, and when detecting electric current output and detect phase current as the microcomputer of input, the signal ground of current detection circuit and microcomputer ground wire are connected a side of parallel resistance, thereby regardless of the electric current that flows through the microcomputer ground wire, the potential change of signal ground can both be prevented, the phase current accuracy of detection can be improved.

Phase current detector according to the twenty-fifth aspect of the invention is when being used for the motor drive that offers motor and drive motor from the output of PWM inverter, use is inserted parallel resistance in the DC link for detecting motor current, current detection circuit, and be used for when detecting electric current output and detect phase current as the microcomputer of input, common mode choke is inserted between current detecting output and the microcomputer ground wire, thereby can prevent that common-mode signal from transmitting, can reduce the noise current that flows through the microcomputer ground wire, improve the phase current accuracy of detection.

Description of drawings

Fig. 1 is the figure that the structure of the motor drive that uses inverter is shown.

Fig. 2 is the figure that applies voltage that applies to motor with two-dimensional representation.

Fig. 3 is the mobile figure that describes of the electric current when the V1 vector is exported.

Fig. 4 is the figure that the electric current that flows through DC link is described.

Fig. 5 is the figure that the actual measurement example of the electric current that flows through DC link is shown.

Fig. 6 is the figure that the structure of the motor drive of using one embodiment of the invention is shown.

Fig. 7 is conceived to resonance at the conceptive figure that Fig. 6 is repainted.

Fig. 8 is the figure that illustrates from the notion circuit structure of the motor drive of current detecting.

Fig. 9 is the figure that the actual measurement example of the electric current that flows through DC link is shown.

Figure 10 is the figure of actual measurement example that flows through the electric current of DC link when being illustrated in length of arrangement wire for 2m.

Figure 11 is the figure that cable length and the relation of ring vibration period are shown.

Figure 12 is the figure that the formation of RC firstorder filter is shown.

Figure 13 is the figure that the response characteristic of RC firstorder filter is shown.

Figure 14 is the figure that the frequency characteristic of RC firstorder filter is shown.

Figure 15 is the figure that is illustrated in the current waveform when omitting filter.

Figure 16 is illustrated in the figure that uses the current waveform when hanging down speed amplifier.

Figure 17 is the figure that the current waveform that is produced by low speed amplifier is shown.

Figure 18 be frequency band be shown be subjected to during the figure of structure of amplifier of capacitance limits.

Figure 19 is the figure that is illustrated in the current waveform when omitting capacitor.

Figure 20 is the figure that is illustrated in the current waveform when capacitor is set.

Figure 21 is the figure of structure that the motor drive of another embodiment that uses phase current detector of the present invention is shown.

Figure 22 is the figure of structure that the motor drive of the another embodiment that uses phase current detector of the present invention is shown.

Figure 23 is the figure that describes the time of delay to each several part.

Figure 24 measures the figure that describes to current waveform.

Figure 25 is the figure that the detection to electric current describes.

Figure 26 is the figure that is illustrated in the DC link electric current when adopting the triangular wave manner of comparison.

Figure 27 is the equivalent circuit diagram of parallel resistance.

Figure 28 is the figure that the parallel resistance characteristic is shown.

Figure 29 illustrates the circuit diagram of the connection status of filter and parallel resistance.

Figure 30 illustrates the figure that inductance is eliminated the characteristic of filter.

Figure 31 is the figure that the characteristic of the current detection circuit with inductance elimination filter is shown.

Figure 32 is illustrated in the figure that eliminates the amperometric determination waveform under the stray inductance state.

Figure 33 is illustrated in the figure that eliminates the amperometric determination waveform under the useless oscillating component state.

Figure 34 is to the parallel resistance under the state of not implementing the noise removing countermeasure and the loop between the amplifier and produces the figure that the relation of magnetic flux describes.

Figure 35 is to making the loop closure between parallel resistance and the amplifier and eliminating the figure that the state of magnetic flux describes in parallel resistance side and amplifier side.

Figure 36 illustrates amplifier is mounted to figure with the parallel plane state of magnetic flux.

Figure 37 is the figure that the conventional connection status of the signal ground of current detection circuit and microcomputer ground wire is shown.

Figure 38 is the circuit diagram that the state of the side that the signal ground that makes current detection circuit and microcomputer ground wire be connected parallel resistance is shown.

Figure 39 illustrates common mode choke is inserted the circuit diagram that detects the state between electric current output and the microcomputer ground wire.

Embodiment

Hereinafter with reference to accompanying drawing, the embodiment of phase current detector of the present invention is elaborated.

Fig. 1 is the figure that the structure of the motor drive that uses inverter is shown.Table 1 shows the relation of the on off state of the output voltage vector of inverter (power device) and switch element.

Table 1

	T _u ⁺ T _v ⁺ T _w ⁺
	T _u ⁺ T _v ⁺ T _w ⁺	V0 V1 V2 V3 V4 V5 V6 V7	OFF OFF OFF OFF OFF ON OFF ON OFF OFF ON ON ON OFF OFF ON OFF ON ON ON OFF ON ON ON

Wherein, T _u ⁺, T _v ⁺, T _w ⁺The switch element of representing the last brachium pontis of u phase, v phase, w phase respectively, T _u ^-, T _v ^-, T _w ^-The switch element of representing the following brachium pontis of u phase, v phase, w phase respectively, in table 1, ON represent the switch element of brachium pontis be ON and down the switch element of brachium pontis be the state of OFF, OFF represents that the switch element of brachium pontis is that the switch element of OFF and time brachium pontis is the state of ON.

In above-mentioned motor drive, being used for AC power 1 is to connect the first capacitor 2a between the lead-out terminal of rectification circuit 2 of input, the three-phase inverter 3 and the first capacitor 2a are connected in parallel, and the output of three-phase inverter 3 is offered motor 4.And at the input side of three-phase inverter 3 second capacitor that is connected in parallel, and between the first capacitor 2a and the second capacitor 3a, connect current detector 5.

This current detector 5 has: parallel resistance 5a, and it is inserted in the wiring between the first capacitor 2a and the second capacitor 3a; And electric current efferent 5b, its voltage between terminals with parallel resistance 5a is input, and as detecting electric current output.

Therefore, when voltage vector is V0 and V7, negative (-) line of all terminals of motor 4 and power supply or just (+) line is connected, and do not apply the voltage (the following voltage that only is called) that electric current is increased and decreased to motor 4.And when voltage vector for example was V1, the terminal of the w phase of motor was connected with just (+) line of power supply, and the terminal of other phases is connected with negative (-) line of power supply, and applied voltage in the direction that the w phase current is increased (u is negative direction mutually with v mutually).

Under the situation of PWM, because the size of voltage is decided by the time ratio of output voltage vector in carrier wave, therefore when the voltage of each phase about equally the time, the voltage vector between the output utmost point short-term suitable (below be referred to as voltage vector lack) with each voltage difference between mutually.And, when output voltage is low, the voltage vector that output is short especially, and not during motor 4 applies the voltage vector V0 of voltage and V7 and takies major part in the carrier wave.

Fig. 2 is the figure that applies voltage that applies to motor 4 with two-dimensional representation.Applying positive voltage to u mutually and mutually being defined as u phase direction, define v phase direction and w direction mutually equally, and voltage swing is represented with vector length with the situation that w applies negative voltage mutually to v.

In the case, voltage vector V0～V7 disposes as shown in Figure 2, for example, when output is clipped in a vector between voltage vector V1 and the voltage vector V3, use general means of space vector representation, for example, in order appropriate change voltage vector, export this voltage vector according to V0, V1, V3 and V7.

When reducing output voltage (shortening vector length),, can make the ratio of the output time of voltage vector V1 and V3 keep constant for output time that prolongs voltage vector V0 and V7 and the direction of preserving a vector.

When from DC link detection phase current, for example, when output a vector, use is during output voltage vector V1, the w phase current flows through DC link (with reference to the arrow among Fig. 3), during output voltage vector V3, the positive and negative opposite electric current of u phase current flows through this character of DC link, can detect phase current { with reference to Fig. 4 from DC link, and people such as " PWM ィ Application バ one three-phase exert oneself Electricity stream direct current Side In detect method (detection method of the DC side of the three-phase output current of PWM inverter) " Gu swamp, IEa-94-17 (hereinafter referred to as list of references) }.

If consider actual current detecting, then change to from current value have under the stable transition state of circuit unmeasured during (with reference to Fig. 5).Therefore, must shorten transition state, so that there is not useless pulse restrictedly to measure electric current as far as possible.

The difference of the motor drive of this motor drive and Fig. 1 only is: the upstream side slightly at current detector 5 also is provided with the 3rd capacitor 3b, and the 3rd capacitor 3b and the first capacitor 2a are connected in parallel; And must be as far as possible little in the scope that the surge voltage that power device can not cause owing to switch is damaged the capacitance settings of the second capacitor 3a.

The effect of the motor drive of said structure is as described below.

Carry out rectification from the power of AC power 1 input by rectification circuit 2, carry out smoothing by the first capacitor 2a then, and be provided for inverter 3, be provided for motor 4 according to voltage vector then.

Then, in order to protect the power device of inverter 3, the second capacitor 3a be arranged on power device near, and make from the second capacitor 3a as far as possible little to the inductive component of power device.

And because the first capacitor 2a is big electric capacity capacitor, thereby the length of arrangement wire between the first capacitor 2a and the 3rd capacitor 3b is longer.

Fig. 7 is conceived to resonance and figure that Fig. 6 is repainted.Between the first capacitor 2a and the 3rd capacitor 3b, be connected with the inductance 2b and the 2c that produce by wiring.

As can be seen from Figure 7, if between the combined capacity of the inductance 2b that produces by wiring between the first capacitor 2a and the 3rd capacitor 3b and 2c, the second capacitor 3a and the 3rd capacitor 3b, produce resonance, and the capacitance settings of the second capacitor 3a and the 3rd capacitor 3b be equal extent (for example, about 1 μ F), then the ringing current that the cycle is long and electric current is big can flow through current detector 5.

Yet, in the present embodiment, because in the scope that the surge voltage that power device can not cause owing to switch is damaged, must be as far as possible little the capacitance settings of the second capacitor 3a, thereby can make the electric current ring that causes by resonance can not flow through current detector 5 substantially, and then can improve current detection accuracy.

And, resonance current is decided by the inductance 2b and 2c, motor phase current, the second capacitor 3a and the 3rd capacitor 3b that are produced by wiring between the first capacitor 2a and the 3rd capacitor 3b, and the resonance current that flows through current detector 5 decides (because resonance current is assigned to the second capacitor 3a and the 3rd capacitor 3b, thereby the resonance current that only flows through the second capacitor 3a just flows through current detector 5) by the capacity ratio of the second capacitor 3a and the 3rd capacitor 3b.

Therefore, if can determine inductance 2b and 2c, motor phase current, the electric capacity of the second capacitor 3a and the electric capacity of the 3rd capacitor 3b between the first capacitor 2a and the 3rd capacitor 3b by the wiring generation, then can calculate the error that causes by the resonance current that flows through current detector 5 easily, yet, but be difficult to the inductance 2b and the 2c that are produced by wiring between the first capacitor 2a and the 3rd capacitor 3b are carried out correct design.Therefore, survey by the error that the resonance current of when maximum (current step during power device ON for) by electric current when maximum is caused, and the capacity ratio of the second capacitor 3a and the 3rd capacitor 3b set for to make the error that is caused by resonance current be below the minimum value of the detection electric current set, can eliminate evaluated error.

And, as mentioned above, under the influence of the second capacitor 3a, the resonance current that is caused by the inductance 2b that is produced by wiring between the first capacitor 2a and the 3rd capacitor 3b and 2c, the second capacitor 3a and the 3rd capacitor 3b flows through current detector 5 and produces error.On the other hand, though it is destroyed owing to the crest voltage of following switch that the second capacitor 3a prevents power device, but because the voltage difference of current detector 5 front and back is very little, thereby by using short as far as possible wiring to connect the 3rd capacitor 3b, current detector 5 and power device, can make the 3rd capacitor 3b bear the function of the second capacitor 3a, and be the capacitance settings of the second capacitor 3a 0.

As a result, can prevent that resonance current from flowing through current detector 5, can be suppressed to the influence of resonance current and be roughly 0.

Between the 3rd capacitor 3b and power device, inductive component in the highest flight, between power device and motor 4, capacitive component is in the highest flight.And motor 4 is made of winding, although have big inductance, if consider the frequency component of ring, then capacitive component in the highest flight.And motor 4 has the stray capacitance that offers stator.Therefore, produce resonance by these inductance and electric capacity.The frequency of this moment is at a high speed with being compared with the resonance phenomena that combined capacity produced of the 3rd capacitor 3b with 2c, the second capacitor 3a by the inductance 2b by the wiring generation between the first capacitor 2a and the 3rd capacitor 3b, and the electric current that flows through as shown in Figure 9, current detector 5 is in internal vibration during voltage vector output beginning of short duration.

Figure 10 shows the measured waveform when length of arrangement wire is set at 2m.

In this observation waveform, under the length of arrangement wire of 2m, observe the resonance frequency about 200ns.This frequency is in a ratio of high speed about 10 times with the resonance phenomena that combined capacity produced by the inductance 2b that is produced by wiring between the first capacitor 2a and the 3rd capacitor 3b and 2c, the second capacitor 3a and the 3rd capacitor 3b, and becomes maximum error component in carrying out the motor drive that the foregoing description handles.

Figure 11 shows according to 4 the wiring from the power device to the motor of this waveform measurement and has or not the relation of the harmonic period of motor 4.

As seen from the figure, the vibration period is owing to the additional of motor 4 increases constant value, and straight line increases along with the increase of length of arrangement wire (cable length).As can be known from Fig. 11, having nearly in the scope of cable length from 2m to 16m, three times cycle changes, consider that 16m sets lower if for example adapt to cut-off frequency, then the required vector length used of current detecting is elongated, and then the filter that is formed by current detector 5 must have the frequency characteristic that adapts to this frequency.

From as can be known above, in the motor drive of the processing of carrying out the foregoing description, can be in the evaluated error scope by being provided with, filter to the ringing frequency component that is produced by 4 wiring and motor 4 from the 3rd capacitor 3b to the wiring of power device, from the power device to the motor fully suppresses can further improve the amperometric determination precision.

And, as this filter, preferably adopt filter with the parts that are used to switch cut-off frequency, by the switching frequency characteristic, but the variation of flexible adaptation length of arrangement wire etc.

Below, this filter is further specified.

Wherein, for the purpose of simplifying the description, be that example describes with RC firstorder filter circuit shown in Figure 12.

The step response characteristic of this RC firstorder filter circuit as shown in figure 13, frequency characteristic is as shown in figure 14.If at the last detection electric current of vector, then basis is by the admissible error Es that detects response speed decision regularly, use when minimum vector length is exported in supposition

1-Es＝{1-exp(-tmin/CR)}

(in the formula, tmin detects the moment regularly)

Relation decide the CR value, and use this to be worth the cut-off frequency f0 that calculates filter.The amplitude Vr of the ring during according to tmin and by the admissible error Es that ring causes calculates the ring amount Es/Vr that should suppress, and obtains ringing frequency fr in view of the above.

Therefore, make more than ringing frequency fr, can improve current detection accuracy by setting from inverter 3 to motor 4 length of arrangement wire.

And Figure 15 shows the measured waveform when not carrying out filtering, and Figure 16 shows the measured waveform that uses when hanging down speed amplifier (25V/ μ s).

With reference to Figure 15 and Figure 16 as can be known, by using low speed amplifier, effective suppressed ringing.In other words, utilize the low pass filter of the through-rate of amplifier, effectively suppressed ringing by use.

Then, if the amplifier that with through-rate is f * Vmax (V/s) is that f, amplitude are that the rectangular wave of Vmax amplifies to frequency, then as shown in figure 17, then become amplitude Vmax/2, become its above big high attenuation of frequency component, and the so-called cut-off frequency that its following frequency component is passed through.

Figure 18 is the circuit diagram of an example that the structure of electric current efferent 5b is shown.

This electric current efferent 5b offers positive input to input signal, and reverse input end is connected with ground wire by resistance 5b2.This electric current efferent 5b has: operational amplifier 5b1 is used for from the lead-out terminal output signal output; And resistance 5b3 and capacitor 5b4, these both connections parallel with one another between reverse input end of operational amplifier 5b1 and lead-out terminal.

Figure 19 shows the measured waveform when omitting capacitor 5b4, and Figure 20 shows the measured waveform when capacitor 5b4 is set.Contrast Figure 19 and Figure 20 as can be known, by capacitor 5b4 is set, can significantly reduce overshoot (overshoot) He Xiachong (undershoot), although and frequency band limited, also can realize high speed.

The difference of the motor drive of this motor drive and Fig. 6 only is, LC series resonant circuit 5c and parallel resistance 5a are connected in parallel.And the resonance frequency that makes this LC series resonant circuit 5c is consistent with the ringing frequency that is produced by 4 wiring and motor 4 from the 3rd capacitor 3b to the wiring of power device, from the power device to the motor.

When adopting this structure, can make the current bypass that causes by ring by the LC series resonant circuit, improve current detection accuracy.

The difference of the motor drive of this motor drive and Fig. 6 is, electric current output from current detector 5 is offered CPU7, port output from CPU7 is offered drive circuit 7a, and the driver output from drive circuit 7a is offered inverter 3 (power device).

When adopting this structure, current detector 5 detects the electric current that flows through DC link successively, and this electric current is offered CPU7.

CPU7 regularly samples to electric current in each current detecting, and detects phase current by the processing shown in list of references.Then, carry out speed control and Current Control etc. and be used for electric motor driven processing, and in drive circuit 7a, specify output voltage vector.Drive circuit 7a comes the switch element of driving power device according to the instruction of CPU7, and voltage (electric current) is offered motor 4.At this moment, the list of references utilization appears at according to the on off state phase current of power device that this situation detects phase current on the DC link, and this motor drive also can detect phase current equally.

When detecting phase current in the motor drive at said structure, shown in list of references, the current detecting of burst pulse is become problem.

Under the situation of output stage burst pulse (voltage vector length is short as far as possible), owing to can not carry out amperometric determination, thereby limit the processing of minimum pulse width (minimum voltage vector length) etc., if but the minimum voltage vector length is elongated, then can produce the voltage vector increase that to export, the problem of voltage (electric current) wave distortion, thereby must set the minimum voltage vector length shortly as far as possible.

As mentioned above the influence of the ring of burst pulse etc. is got rid of, yet, also must be considered the delay that causes by device etc. in order to carry out correct current detecting, make detect regularly consistent with electric current.

Figure 23 shows the delay of each several part.

The delay addition of the delay of the port delay of CPU7, drive circuit 7a and power device as total delay.Postpone although Figure 23 only shows rising edge, produce delay too at trailing edge.

In normally used circuit, these delays are hundreds of ns separately, integrate to be 500ns～1 μ s, and change at double along with temperature, deviation etc.Therefore, when the pulse below considering about 1 μ s limits, can not ignore the variation of time of delay.

Under the circumstances, by one in rising edge time of delay of the electric current that flows through DC link at least corresponding with the instruction of CPU7 or trailing edge time of delay or the current waveform or multinomial relation are measured, and decide current detecting regularly or the minimum voltage vector according to this result, can make detect regularly consistent with electric current.

Further specify with reference to Figure 24.

Figure 24 is the figure that the assay method to current waveform describes, supposes as shown in figure 24 regularly from output order, and through each delay, the output of power output device.

Because current waveform is the repetitive pattern of each PWM, thereby can thinks to repeat to export from output and begin to the asynchronism(-nization) of end of output but the identical waveform of shape by each PWM cycle.

At this moment, if use various current detecting to detect electric current time of delay, then can measure from the output beginning regularly export which kind of waveform to each PWM.To trailing edge also is same, and may observe is from end of output time of delay and waveform regularly.

Therefore, can operate by this and obtain comprehensive rising edge time of delay and trailing edge time of delay, ringing waveform etc. when rising.

Then, shown in (a) among Figure 25, can

The convergence time (to the stable time of circuit) of comprehensive rise time+ringing waveform is set at the current detecting lower limit of time of delay,

Shown in (b) among Figure 25, can

Comprehensive rise time+to circuit stable time-comprehensive fall time

(wherein, be to be timed to the time that trailing edge begins from end of output comprehensive fall time)

The lower limit that is set at minimum vector length gets final product, and can not rely on time of delay, carries out the mensuration of phase current exactly.Certainly, minimum value is to use the situation of each lower limit.

Here, because this mensuration is to use the current detector 5 of the device of Figure 22 to carry out, thereby delay such as detection time of current detector 5 are included in each delay and are detected.

And, preferably when starting, flow through at direct current under the state of motor 4, measuring each time of delay corresponding with the instruction of CPU7.In this case, because current value do not change, and the PWM width do not change yet, thereby can realize correct mensuration.And, owing to after starting, be difficult to make direct current to flow, thereby must when starting, direct current be flowed.

And, preferably in the PWM ripple produces, use the triangular wave manner of comparison, and carry out the mensuration of time of delay corresponding etc. and be used for the amperometric determination that phase current detects with the instruction of CPU7 at the inclined side separately of rising edge trailing edge.

Figure 26 is the figure that the DC link electric current in the triangular wave manner of comparison is shown.

Vn is the example of output voltage vector.In the triangular wave manner of comparison, two symmetrical voltage vectors of output can observe two symmetrical current waveforms in a carrier wave.Therefore, preferably one of them is used for phase current and detects, and another is used for measuring time of delay, thereby always can carry out phase current when measuring time of delay measures, and can improve current detection accuracy.

When in the PWM ripple produces, using the sawtooth waveforms manner of comparison owing to there is not above-mentioned symmetry, thereby can not carry out in a carrier wave that phase current detects and time of delay mensuration.Yet, in this case, carry out mensuration time of delay by suitably stopping the phase current detection, can improve current detection accuracy.

And, can use by above-mentioned each motor drive drive electric motor 4 and drive hermetic type compressor.

Here, hermetic type compressor usually not use location transducer (the use location transducer does not come the method for the position of rotation of detection rotor) drive.And in recent years, owing to use phase voltage, phase current and machine constant to come the technology of detection rotor position of rotation constantly to develop, thereby to use the various embodiments described above that can correctly detect phase voltage according to the DC link electric current be effective.

And, owing to hermetic type compressor adopts the structure of motor configurations in the space of sealing cold-producing medium and refrigerator oil, thus also high in the permittivity ratio air, so the embodiment of application drawing 8 to Figure 26 is effective especially.

Below will the embodiment that use parallel resistance to carry out the phase current detection be described.

Figure 27 is the figure that the equivalent electric circuit of parallel resistance is shown, and resistive component Rs and stray inductance Ls are connected in series.

Therefore, suppose that the electric current that flows through parallel resistance is Is, frequency is ω, and then stray inductance produces the electromotive force of j ω LsIs, causes producing evaluated error.Because high more this error of high frequency components is big more, thereby when the high speed amperometric determination of carrying out pulse current and so on, especially becomes big problem.

Figure 28 shows Rs=0.0025 Ω, Ls=10e ^-9The time from Is to the voltage that is detected the Bode diagram of the transfer function of (Rs+j ω Ls) Is.As can be seen from Figure 28, when about 40kHz, there is zero point, and amplitude increase when the above frequency of this value.When the common current detection circuit of design, carry out frequency band limits by current detecting frequency band and reduce noise necessity.When measuring pulse current, the current detecting frequency band about 1MHz is necessary, and therefore, the problem of existence is a high-frequency current can become noise having on the parallel resistance at this zero point, thereby can not carry out correct amperometric determination.

Therefore,, can eliminate this influence, and can carry out correct and current detecting at a high speed by in current detector, being provided for eliminating the filter of the electromotive force that causes by stray inductance Ls.

Figure 29 shows an example of this circuit structure, and the output of parallel resistance is provided with the RC filter.

Here, capacitor Cc and resistance R c that the electromotive force of selecting elimination to be caused by stray inductance Ls is used are to satisfy the relation of CcRc=Ls/Rs.

At this moment, be 1/ (j ω CcRc+1) from the voltage that produces in parallel resistance to the transfer function of exporting V0.

If represent Cc=0.1e with Bode diagram ^-6Then as shown in figure 30, there is limit in transfer function when F, Rc=40 Ω at about 40kHz place as can be known.

This moment, the transfer function from electric current I s to output V0 was

V0＝(Rs+jωLs)Is/(1+jωCc(Rs+Rc)-ω ²LsCc)，

Characteristic is a falt characteristic when height is above to 100MHz as shown in figure 31, and in the characteristic of high-frequency region for decay, thereby do not have noise effect, can measure phase current with very high degree of precision.

That is to say,, can obtain the above falt characteristic of 100MHz by limit being set in the frequency (for example 40kHz) lower than the desired frequency band of current detection circuit (for example 1MHz).

And,, thereby, can be shaped as intended shape to frequency characteristic by keeping some deviations because the deviation of pole and zero shows as the gain inequality on the frequency height.

For example, by making limit, can make high-frequency gain greater than low-frequency gain, and can emphasize pulse rising edge greater than zero point.Yet, if deviation is excessive, can produce evaluated error, thereby preferably in the scope that does not produce evaluated error, adjust.

And the current component of the mensuration of obstruction ringing current etc. flows through parallel resistance, by to the further filtering of this component, can realize the high-precision measuring that error is minimum.The real machine that Figure 32 shows when eliminating stray inductance Ls is measured waveform, and the real machine that Figure 33 shows when having eliminated useless oscillating component is measured waveform.From Figure 32 and Figure 33 as can be known, by implementing two kinds of filtering, can carry out fabulous amperometric determination.

As mentioned above, there is following situation, that is: the zero point that produces tens of kHz owing to inductive component parasitic on parallel resistance.Therefore, when mensuration has the pulse current of several MHz components, can produce big crest voltage, when this crest voltage being directly inputted to active elements such as amplifier, can be subjected to the limitations affect of the through-rate of amplifier and dynamic range and can not correctly amplify, perhaps must use very expensive circuit structure.

Therefore,, this waveform is input to active elements such as amplifier, can carries out amperometric determination, and can not produce the problems referred to above by be shaped as the waveform that is fit to measure in advance by filter after.

In addition, although can consider filter be arranged on get the bigger active elements such as amplifier of dynamic range later the level, yet since filter be difficult to integrated, thereby when making current detector integrated existing problems.Because in this case, above-mentioned filter also can observe fabulous current waveform, thus by filter is set directly at parallel resistance near, can make the later circuit integration of filter.

And as shown in figure 34, if electric current flows through parallel resistance, then its periphery produces magnetic flux.And if this magnetic flux then produces electromotive force by by in the circuit-formed loops such as parallel resistance two ends and amplifier, become noise, and produce evaluated error.Therefore, usually, by little this noise that reduces of must trying one's best loop design, still, loop reduce but owing to the restriction of parallel resistance size etc. with have limit with the relevant restriction in position etc. of being provided with of amplifier.Yet,, noise is reduced by being provided for eliminating the noise removing portion of the electromotive force that causes by interlinkage flux.

Figure 35 shows an example of this situation.Here, adopt to make the loop closure that forms by wiring, in the structure of parallel resistance side and amplifier side elimination magnetic flux.Therefore, the electromotive force that causes by interlinkage flux can be eliminated, current detection accuracy can be improved.

Figure 36 shows the mounting structure of not accepting the noise that caused by magnetic flux.Here, by the plane parallel of current arrangements one-tenth, can realize the structure that not influenced by magnetic flux with the magnetic flux that causes by electric current.

And, when carrying out wiring shown in Figure 37 (the conventionally wiring of generally not carrying out), measure electric current generation error owing to the dead resistance in noise current and the wiring makes.Though by employing above-mentioned noise removing portion is set, and does not accept noise or can avoid the mounting structure of noise, can reduce the noise that in the current detection circuit input, produces,, it is very difficult reducing the noise current that flows through the microcomputer ground wire.Therefore, as shown in figure 38, the end that signal ground by making current detection circuit and microcomputer ground wire are connected parallel resistance, the electric current that can prevent to flow through the microcomputer ground wire changes the current potential of signal ground and becomes noise, can carry out correct amperometric determination.

And, as shown in figure 39,, can prevent that common-mode signal from transmitting by being equipped with common mode choke, can reduce the noise current that flows to the microcomputer ground wire, and prevent that noise from producing.

Invention according to a first aspect of the invention can reach and make the electric current ring that caused by resonance can the current flowing detector, can improve the peculiar effect of current detection accuracy.

Invention according to a second aspect of the invention can reach and significantly reduce evaluated error, improves the peculiar effect of amperometric determination precision.

Invention according to a third aspect of the invention we can reach the impact of resonance current is suppressed to and be roughly 0, improves the peculiar effect of amperometric determination precision.

Invention according to a forth aspect of the invention can reach in the evaluated error scope ringing frequency component is fully suppressed, and improves the peculiar effect of amperometric determination precision.

But invention according to a fifth aspect of the invention also can reach and same according to a forth aspect of the invention effect except the variation of flexible adaptation length of arrangement wire etc.

Invention according to a sixth aspect of the invention can reach the ringing frequency component is fully suppressed, and improves the peculiar effect of amperometric determination precision.

Invention according to a seventh aspect of the invention can reach the effect same with the 6th aspect.

Invention according to an eighth aspect of the invention can reach the effect same with the 7th aspect.

Invention according to a ninth aspect of the invention can significantly reduce overshoot and undershoot, can reach and any one same effect to the eight aspect according to a first aspect of the invention.

Invention according to the tenth aspect of the invention can reach and reduce the ring impact, improves the peculiar effect of current detection accuracy.

Invention according to an eleventh aspect of the invention can reach the impact that reduces the delay that caused by parts etc., improves the peculiar effect of current detection accuracy.

Invention according to a twelfth aspect of the invention can be able to not change and the PWM width is also measured time delay under the indeclinable state at current value, and then improves the peculiar effect of current detection accuracy.

Invention according to a thirteenth aspect of the invention always can reach can carry out current detecting when measuring time delay, can improve the peculiar effect of current detection accuracy.

Even invention according to a fourteenth aspect of the invention can reach when adopting without symmetric mode, also can suitably stop the phase current detection and carry out mensuration time delay, can improve the peculiar effect of current detection accuracy.

Invention according to a fifteenth aspect of the invention can reach and any one same effect in according to a fourteenth aspect of the invention according to a first aspect of the invention when driving hermetic type compressor.

Invention according to a sixteenth aspect of the invention can reach the peculiar effect that improves the phase current accuracy of detection.

Invention according to a seventeenth aspect of the invention can reach and reach falt characteristic in wide region, and then can improve the peculiar effect of phase current accuracy of detection.

Invention according to an eighteenth aspect of the invention can reach and reach falt characteristic in wide region, and then can improve the peculiar effect of phase current accuracy of detection.

Invention according to a nineteenth aspect of the invention also can reach and any one same effect to the tenth eight aspect according to a sixteenth aspect of the invention except the impact that can get rid of useless oscillating component.

Invention according to a twentieth aspect of the invention can be adopted the inexpensive construction that is difficult to produce by the non-linear error that causes, reaches and any one same effect to the 19 aspect according to a sixteenth aspect of the invention.

Invention according to a twenty-first aspect of the invention can reach the peculiar effect that improves the phase current accuracy of detection.

Invention according to a twenty-second aspect of the invention can reach the peculiar effect that improves the phase current accuracy of detection.

Invention according to a twenty-third aspect of the invention can reach and same according to a twenty-second aspect of the invention effect.

Invention according to a twenty-fourth aspect of the invention can reach no matter the electric current that flows through the microcomputer ground wire how, all can prevent the potential change of signal ground, improves the peculiar effect of phase current accuracy of detection.

Invention according to the twenty-fifth aspect of the invention can reach and prevent that common-mode signal from transmitting, and reduces the noise current that flows through the microcomputer ground wire, improves the peculiar effect of phase current accuracy of detection.

Claims

1, a kind of phase current detector, this phase current detector is offering the output from PWM inverter (3) in the motor drive of motor (4) and drive motor (4), uses parallel resistance that the electric current that flows through DC link is detected; It is characterized in that,

Make the loop closure that forms by parallel resistance two ends and amplifier.