CN100346571C - Energy-saving speed regulating technique for three-phase asynchronous motor - Google Patents

Abstract

The present invention provides an energy saving technique for regulating the speed of a three-phase asynchronous motor, which has the advantages of high efficiency and energy saving. The technique comprises: voltage U and frequency f are regulated separately and independently, the unique corresponding frequency f satisfying the reasonable active and reactive match is determined according to the rotary speed n of a motor, and simultaneously, the voltage U is determined according to requirements for the load torque of a motor; when the rotary speed is decreased to a certain degree, the amplitude of magnetic flux is limited if the air gap magnetic flux exceeds the rated value by 25%, and the air gap magnetic flux is regulated according to an equality that U/f is a constant under the condition of keeping the air gap magnetic flux 1.25 time of the rated value. If the technique is implemented according to a control block diagram disclosed in the specification, the energy saving control of a three-phase asynchronous motor can be realized, and the running efficiency of a three-phase asynchronous motor can be enhanced by about 1 to 6% on the original basis.

Description

The speed regulating method of threephase asynchronous

Technical field:

The present invention relates to a kind of speed adjusting technique of threephase asynchronous, relate in particular to a kind of energy-saving speed adjusting technique.

Background technology:

The speed adjusting technique of existing asynchronous motor all is external the proposition, and China does not also have the speed adjusting technique of independent intellectual property right.Existing speed adjusting technique all is to be target with the speed adjusting performance that obtains, aspect energy-conservation, do not put forth strength, and all with DC speed regulation as contrasting, emphasize that the maintenance air-gap flux is constant when rated speed and following operation, promptly

Then weak magnetic when more than rated speed, moving.In laying claim to several technology of energy-saving effect, all be to emphasize a certain technology side, the overall situation from energy delivery does not consider a problem, so effect is general.

Summary of the invention:

The objective of the invention is to overcome the above-mentioned defective of existing in prior technology, a kind of speed regulating method of energy-efficient threephase asynchronous is provided.

Technical scheme of the present invention is as follows: it is characterized in that: voltage U and frequency f are separated independent regulation, thereby determine to satisfy unique respective frequencies f meritorious, idle rational Match is moved motor under maximal efficiency according to motor speed n, determine that according to the needs of electric motor load torque voltage U makes the active current component I that is produced by it simultaneously _StWith reactive current component I _{S φ}Electromagnetic torque of being set up and load torque balance are to guarantee that motor moves under the rotating speed of appointment.

Implement according to controlling party block diagram proposed by the invention, can realize, make its operational efficiency improve 1-6% on the original basis the threephase asynchronous Energy Saving Control.If this power-saving technology is applied, considerable energy-saving effect will be brought.For the world of current energy growing tension, the technology of the present invention is significant undoubtedly.

Description of drawings:

Fig. 1 is a threephase asynchronous equivalent circuit used in the present invention.

Fig. 2 is the Energy Saving Control block diagram of threephase asynchronous proposed by the invention.

Embodiment:

Technical characterstic of the present invention:

1, the present invention looks at problem from the overall situation of energy converting between mechanical and transmission, thinks that the electromagnetic torque of motor is crucial in the process of the conversion of energy and transmission, and electromagnetic torque is produced by the interaction of magnetic field and electric current, and magnetic field is set up by the reactive power of motor.It is meritorious reasonable with idle coupling in when operation if can control motor, and motor just can move under maximal efficiency, thereby reaches energy-conservation purpose.

2, to control the meritorious and idle rational Match of motor, must be earlier with its decoupling zero.For this reason, the present invention uses equivalent circuit as shown in Figure 1.The used equivalent circuit basically identical of vector control in this circuit and the general technology document, only the present invention equivalent parallel excitation resistance aR that will have been ignored by them, the reflection iron loss has mended.When considering energy problem, iron loss should not ignored.

3, in equivalent circuit, when input voltage U determines, active current component I _StCan represent active power, the reactive current component I of motor _{S φ}Then can represent reactive power, establishing λ is the ratio of the active power and the reactive power of motor, then has $\mathrm{\λ}=\frac{\mathrm{mU}{I}_{\mathrm{st}}}{\mathrm{mU}{I}_{\mathrm{s\φ}}}=\frac{I_{\mathrm{st}}}{I_{\mathrm{s\φ}}}=\frac{L_r}{r_r}\mathrm{s\ω},$ Angular frequency in the formula=2 π f, revolutional slip $s=\frac{60f-\mathrm{pn}}{60f},$ Wherein p is the motor number of pole-pairs, is known constant for making good motor; Obviously, λ and frequency f have one-to-one relationship when motor speed n determines.Like this, when determining, motor speed n just can reach the meritorious and idle ratio λ of control motor by control frequency f.

4, the electromagnetic torque T=k of motor _TI _StI _{S φ}, by the visible I of equivalent circuit _StWith I _{S φ}The way of big or small available change input voltage U control.

5, by above explanation, the present invention proposes Energy Saving Control block diagram as shown in Figure 2.The represented technical characterstic of this block diagram is:

(A) have two control rings, first frequency loop, according to rotating speed of motor with and the frequency of the corresponding idle control inverter recently of rationally gaining merit of this rotating speed: it two is electric current loops, by transfer I _StWith I _{S φ}Value make the electromagnetic torque and the load balance of motor, move under the rotating speed of appointment to keep motor.

(B) U and f independent regulation generally do not keep

(C) when low cruise, if during air-gap flux overrate 25%, magnetic flux is taked the amplitude limit measure, at this moment press

Regulate, but air-gap flux will be 1.25 times of rated value.

Claims (2)

1, a kind of speed regulating method of threephase asynchronous, it is characterized in that: voltage U and frequency f are separated independent regulation, thereby determine to satisfy unique respective frequencies f meritorious, idle rational Match is moved motor under maximal efficiency according to motor speed n, determine that according to the needs of electric motor load torque voltage U makes the active current component I that is produced by it simultaneously _StWith reactive current component I _{S φ}Electromagnetic torque of being set up and load torque balance are to guarantee that motor moves under the rotating speed of appointment.

2, the speed regulating method of threephase asynchronous according to claim 1 is characterized in that: when low cruise, if during air-gap flux overrate 25%, magnetic flux is taked the amplitude limit measure, at this moment press

Regulate, but air-gap flux will be 1.25 times of rated value.

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