CN203941226U

CN203941226U - Adopt the N of dual power supply to hold single resistor current circuit for detecting

Info

Publication number: CN203941226U
Application number: CN201420318670.3U
Authority: CN
Inventors: 谢晓东
Original assignee: Taian Technology (Wuxi) Co Ltd
Current assignee: Taian Technology (Wuxi) Co Ltd
Priority date: 2014-06-13
Filing date: 2014-06-13
Publication date: 2014-11-12
Anticipated expiration: 2024-06-13

Abstract

The utility model discloses a kind of N that adopts dual power supply and hold single resistor current circuit for detecting, comprise frequency converter DC-AC main circuit part and hardware amplification circuits; Frequency converter DC-AC main circuit part comprises the three-phase inverter being made up of the IGBT power model of three Unit two, and output terminal U, V, the W of three-phase inverter are connected with motor, are in series with sampling resistor on DC bus; Hardware amplification circuits comprises dual power supply amplifier and voltage follower; After bus current flows through sampling resistor, through hardware amplification circuits and on lift after 2.5V, sample for the AD module of CPU.The utility model carries out the reconstruct of electric machine phase current based on the mode of single resistance sampling DC bus current, can reduce costs, reduce volume, raise the efficiency.

Description

Adopt the N of dual power supply to hold single resistor current circuit for detecting

Technical field

The utility model relates to inverter current detection techniques, relates in particular to a kind of N that adopts dual power supply and holds single resistor current circuit for detecting.

Background technology

In the close-loop control scheme of frequency converter AC speed regulating, it is a core link that motor three-phase current is sampled.Current inverter current detecting often makes Current Transformer carry out sampling frequency converter output current, and so not only cost is high, and frequency converter volume also can be larger.Along with the development of converter technique, existing inverter current detecting mode can not meet the demands.

Utility model content

The utility model aims to provide a kind of N that adopts dual power supply and holds single resistor current circuit for detecting, thereby reduces costs, reduces volume, raise the efficiency.

The technical solution of the utility model is as follows:

Adopt the N of dual power supply to hold a single resistor current circuit for detecting, comprise frequency converter DC-AC main circuit part and hardware amplification circuits;

Described frequency converter DC-AC main circuit part comprises the three-phase inverter being made up of the IGBT power model of three Unit two, and output terminal U, V, the W of three-phase inverter are connected with motor, on the DC bus of three-phase inverter, are in series with sampling resistor;

Described hardware amplification circuits comprises dual power supply amplifier and voltage follower; The in-phase input end of dual power supply amplifier is connected and is connected the DC bus of frequency converter DC-AC main circuit part after described sampling resistor, the inverting input of dual power supply amplifier is connected and is held after the first resistance connecting analog, the second resistance is connected between the inverting input and output terminal of dual power supply amplifier, dual power supply amplifier is also connected with respectively the first drop-down electric capacity, the second electric capacity with the in-phase input end that is connected voltage follower after output terminal series connection the 3rd resistance, the positive-negative power end employing ± 15V power supply of dual power supply amplifier; The in-phase input end of voltage follower is connected with the 4th resistance drawing, and the 5th drop-down resistance and the 3rd electric capacity, the inverting input of voltage follower and output terminal short circuit, and the output terminal of voltage follower connects CPU and is connected with the 4th drop-down electric capacity.

Useful technique effect of the present utility model is:

The mode of the utility model based on single resistance sampling DC bus current, carries out the reconstruct of electric machine phase current, can reduce costs, reduces volume, raise the efficiency.

Brief description of the drawings

Fig. 1 is frequency converter DC-AC main circuit part schematic diagram.

Fig. 2 is voltage signal and the output current wave figure on sampling resistor.

Fig. 3 is hardware amplification circuits schematic diagram.

Fig. 4 is the voltage oscillogram of CPU end.

Embodiment

Below in conjunction with accompanying drawing, embodiment of the present utility model is described further.

Fig. 1 is frequency converter DC-AC main circuit part schematic diagram, and wherein three-phase inverter is made up of the IGBT power model of three Unit two, and resistance R is to detect the sampling resistor of DC side bus current, and output terminal U, V, the W of frequency converter are connected with motor.

Voltage signal and output current wave on actual test resistance R are shown in Fig. 2.(CH1 is voltage on detecting resistance, CH2, and CH3, CH4 is frequency converter output current wave)

After bus current Idc flows through sampling resistor R, through hardware amplification circuits as shown in Figure 3 and on lift after 2.5V (signal magnitude is between 0～5V), sample for the AD module of CPU.

Hardware amplification circuits as shown in Figure 3, adopts dual power supply amplifier IC202A, and model is TL3474, and amplifier employing ± 15V power supply is little for positive negative signal magnification distortion.Computation process is as follows:

The empty short V-=V+=Vin that obtains breaks and can draw I1=I2 because empty, because can obtain

-Vin/R260＝(Vin-V1)/R265

V1＝(1+R265/R260)*Vin

V1＝23*Vin

Because of Vin=Idc*R

Actual detecting resistance is 30m Ω, so Vin=0.03*Idc, V1=0.69*IdcV2 point voltage can be calculated by node voltage:

V2＝(AVCC/R283+V1/R268)/(1/R283+1/R268+1/R279)

V2＝(5/1+V1/2)/(1+1/2+1/2)

V2＝2.5+0.25*V1

V2＝2.5+0.1725*Idc

Because IC202C is voltage follower, so output voltage V 0=V2=2.5+0.1725*Idc, it is V0 that actual CPU records voltage, actual test voltage value is as Fig. 4, as shown in Figure 4, by the conversion of hardware circuit, DC bus current is converted to centered by 2.5V, the voltage signal of amplitude 0～5V, provides software needed processing signals.(CH3 is output PWM drive waveforms for CH1, CH2, and CH4 is that CPU detects the bus current obtaining).

The components and parts that form above circuit are commercial goods.

Foregoing circuit, by amplification and conversion to bus current, has obtained software and has processed needed signal, has completed the function of hardware circuit.Next can, according to the relation between phase current, DC bus current and inverter switching states, carry out reconstruct three-phase current by the method for space voltage vector phase shift, this reconfiguration technique is prior art, does not explain in detail herein.

Above-described is only preferred implementation of the present utility model, and the utility model is not limited to above embodiment.Be appreciated that the oher improvements and changes that those skilled in the art directly derive or associate under the prerequisite that does not depart from spirit of the present utility model and design, within all should thinking and being included in protection domain of the present utility model.

Claims

1. adopt the N of dual power supply to hold a single resistor current circuit for detecting, it is characterized in that: comprise frequency converter DC-AC main circuit part and hardware amplification circuits;