CN205263190U - Current detection device based on converter direct current side for speed reducer - Google Patents

Abstract

The utility model discloses a current detection device based on converter direct current side for speed reducer, including rectifier, filter circuit, converter, motor and singlechip, the input of rectifier with exchange ferroelectric phase even, the output of rectifier links to each other with the input of converter through filter circuit, the output of converter links to each other with the motor, be equipped with the sampling resistor between filter circuit and the converter, the input termination of singlechip is between sampling resistor and converter, and the output of singlechip links to each other with the converter. The utility model discloses a sampling resistor is gathered converter direct current bus current and is sent into the singlechip, and according to measuring direct current, the singlechip utilizes direct current's peak value can calculate output current's size to control the motor, realize protections such as transshipping, overflow, reach anticipated purpose, accurate measuring converter output current the time, taken into account for the speed reducer requirement of converter to performance, cost, volume.

Description

Current sensing means based on reductor with frequency converter DC side

Technical field

The utility model relates to field of power electronics, particularly a kind of current sensing means of using frequency converter DC side based on reductor.

Background technology

Reductor is one of mechanical part conventional in engineering machinery, and its application in revolution and the machinery that hoists is more extensive, and the performance of reductor directly has influence on the overall quality of engineering machinery. in the reductor of use induction machine, use the frequency converter of controlling induction machine rotating speed, as shown in Figure 1, traditional frequency conversion device current sample structure comprises rectifier 1, filter capacitor 2, frequency converter 3, single-chip microcomputer 4 and motor 5, frequency conversion, 3 general principles that realize vector controlled are by measuring and control motor 5 stator current vectors, according to field orientation principle, the exciting current to motor 5 and torque current are controlled respectively, thereby reach the object of controlling motor torque, frequency converter 3 need to detect the stator current of motor 5, the namely output current of frequency converter 3, be used for improving Electric Machine Control effect and for overcurrent, overload, the defencive functions such as short circuit, stator phase current detects the effect that whether accurately directly has influence on Electric Machine Control.

Conventionally the electric current detecting method of frequency converter is to use Hall current sensor, Hall element current sample method is to use 2-3 Hall element, phase current when motor is moved is converted into voltage signal, sends to after treatment control kernel, completes phase current Bian sample. Use Hall element to carry out current sample and there is lot of advantages, as high in sampling precision, electrical isolation performance is good, current signal is processed simple etc., but Hall element cost is higher, and volume is larger, the output current value that detects frequency converter forms electric current loop as feedback current, the closed-loop control of composition current inner loop, in the use of reductor, detecting current device all has higher requirements to cost volume, it is not the most desirable using Hall current sensor, is not suitable for being used in low cost and hardware space is limited to larger application scenario.

Also having some occasion samplings is 2-3 the sampling resistors of lower brachium pontis series connection at inverter circuit, by the sample reconstruction of Bian sample resistance both end voltage being gone out to phase current in particular moment, the advantage of the method is that structure is comparatively simple, cost is low etc., but the method need to just can be carried out current sample under specific zero vector, be not suitable for the application scenario that uses SPM. Also having reference model self-adaptive current Reconstruction Method is by motor model, phase current to be observed, this method is very large to the dependence of motor model, also comparatively responsive to parameter, it is larger that the phase current levels of precision reconstructing is subject to above-mentioned both impacts, and practicality is lower.

Summary of the invention

In order to solve the problems of the technologies described above, the utility model provides a kind of simple in structure, volume is little, certainty of measurement is high based on reductor frequency converter DC side current sensing means.

The technical scheme that the utility model addresses the above problem is: a kind of current sensing means of using frequency converter DC side based on reductor, comprise rectifier, filter circuit, frequency converter, motor and single-chip microcomputer, the input of described rectifier is connected with alternating current, the output of rectifier is connected with the input of frequency converter through filter circuit, the output of frequency converter is connected with motor, between described filter circuit and frequency converter, be provided with sampling resistor, the input of described single-chip microcomputer is connected between sampling resistor and frequency converter, and the output of single-chip microcomputer is connected with frequency converter.

The beneficial effects of the utility model are: sampling resistor of the present utility model is between filter circuit and frequency converter, gather frequency changer direct current bus electric current and send into single-chip microcomputer by sampling resistor, the information that DC current has comprised output current, according to the DC current of measuring, single-chip microcomputer utilizes the peak value of DC current can calculate the size of output current, thereby motor is controlled, realize overload, the protections such as overcurrent, accomplish the end in view, when accurately detecting frequency converter output current, take into account reductor frequency converter to performance, cost, the requirement of volume.

Brief description of the drawings

Fig. 1 is traditional frequency conversion device current sample structure chart.

Fig. 2 is structural representation of the present utility model.

Fig. 3 is current simulations waveform of the present utility model and three-phase output current comparison diagram.

Detailed description of the invention

Below in conjunction with drawings and Examples, the utility model is further described.

As shown in Figure 2, the utility model comprises rectifier 1, filter circuit, frequency converter 3, motor 5 and single-chip microcomputer 4, the input of described rectifier 1 is connected with alternating current, the output of rectifier 1 is connected with the input of frequency converter 3 through filter circuit, filter circuit adopts filter capacitor 2, the output of frequency converter 3 is connected with motor 5, between described filter circuit and frequency converter 3, be provided with sampling resistor R, the input of described single-chip microcomputer 4 is connected between sampling resistor R and frequency converter 3, and the output of single-chip microcomputer 4 is connected with frequency converter 3.

Sampling resistor R gathers frequency converter 3 DC bus currents and sends into single-chip microcomputer 4; the information that DC current has comprised output current; according to the DC current of measuring; single-chip microcomputer 4 utilizes the peak value of DC current can calculate the size of output current; thereby motor 5 is controlled, realized the protections such as overload, overcurrent, accomplish the end in view; when accurately detecting frequency converter output current, take into account the requirement of reductor frequency converter to performance, cost, volume.

In each cycle of frequency converter output current, on bus, there are 6 bus current maximums identical with output current maximum. Gather bus current value by sampling resistor R, can within the unit interval, detect the maximum of bus current, calculate output current. In this unit interval, at least to comprise 1 bus current maximum, be for 1/6 output current cycle. While supposing frequency converter output 50Hz, the cycle is 20ms, only needs 20/6ms=3.3ms just can sample a maximum. But being output as 1Hz when frequency converter is that the cycle is 1s, just needs 1000/6ms=166.7ms just can sample a maximum. It is that The faster the better that current detecting requires, and current precision simultaneously will ensure 1Hz time, preferably just fixes on 166.7ms so calculate the peaked unit interval. In practice, reduce clutter error, ensure current detecting accurate stable, can not only get a maximum, generally will get multiple maximums, ask its mean value as actual value. So have a problem again, get peaked number more, the time is just more of a specified duration, and current-responsive is just slower, and number can not be eliminated again error very little. Such as getting 4 maximums, at least need 166.7 × 4ms. For addressing this problem, the utility model is taked a kind of slip array filtering algorithm, if get equally 4 maximums, distinguishes assignment to Max1, Max2, and Max3, tetra-variablees of Max4, get their mean value afterwards. Now first maximum is assigned to Max1～Max4 simultaneously, often calculate afterwards after a maximum, just this maximum is assigned to Max1, before the value of preserving in Max1 be assigned to Max2, by that analogy, the value of last old Max4 is just rejected, and the time also only needs 166.7ms like this, ensure current response rate, eliminated error effect simultaneously by averaging.

The utility model is at a 220V, and the reductor that power is 1Kw is with testing on frequency converter. As shown in Figure 3, in figure, 6 is dc bus sample rate current waveform, 7 is output current phase waveform, frequency is 50Hz, load current is from no-load current to 150% frequency converter rated current, calculating electric current and measured current poor be Δ I < 0.3A, and error mainly concentrates on unloaded section of low frequency, and all the other section of precision is higher. Visible this kind of method is specially adapted to reductor frequency converter, it meets the requirement to frequency converter output electric current measure precision in reductor application completely, having taken into account the requirement of reductor frequency converter to performance, cost, volume, is a kind of more satisfactory solution.

Claims (1)

1. use the current sensing means of frequency converter DC side based on reductor for one kind, it is characterized in that: comprise rectifier, filter circuit, frequency converter, motor and single-chip microcomputer, the input of described rectifier is connected with alternating current, the output of rectifier is connected with the input of frequency converter through filter circuit, the output of frequency converter is connected with motor, between described filter circuit and frequency converter, be provided with sampling resistor, the input of described single-chip microcomputer is connected between sampling resistor and frequency converter, and the output of single-chip microcomputer is connected with frequency converter.