CN201527447U

CN201527447U - Current crossover point detection device for an electric machine soft starter

Info

Publication number: CN201527447U
Application number: CN2009201009084U
Authority: CN
Inventors: 李超; 刘志强; 赵书强; 何晓平; 张德海; 丁兆国; 周维来
Original assignee: Harbin Jiuzhou Electric Co Ltd
Current assignee: Harbin Jiuzhou Electric Co Ltd
Priority date: 2009-09-21
Filing date: 2009-09-21
Publication date: 2010-07-14
Anticipated expiration: 2019-09-21

Abstract

A current crossover point detection device for an electric machine soft starter comprises a window comparison circuit unit, a capacitor resistor unit, a shaping circuit unit and a pulse width adjustment unit, characterized in that: the window comparison circuit unit is connected with the capacitor resistor unit, the capacitor resistor unit is connected with the shaping circuit unit and the pulse width adjustment unit is also connected with the shaping circuit unit. The window comparison circuit unit is composed of a voltage comparator and compares the input alternate current signal with the given voltage interval. When the input signal is in the voltage interval, the whole system outputs a high level signal; when the input signal is not in the voltage interval, a low level signal is output. The current crossover point detection device solves the problem that the current crossover point of the electric machine soft starter is not accurately collected and makes the soft starter capable of receiving accurate crossover signal, therefore the trigger pulse is accurately sent to turn on controlled silicon and thus the start of the electric machine is more reliable.

Description

A kind of current over-zero point detection device that is used for motor soft starter

Technical field

The utility model relates to a kind of pick-up unit, is specifically related to a kind of current over-zero point detection device that is used for motor soft starter.

Background technology

Nowadays the electric machine soft starting device has obtained using widely, wherein current limliting closed loop start mode can limit the starting current times of motor accurately, from truly having realized electric machine soft starting, it becomes topmost start mode in the soft start control system.But owing to adopted current closed-loop when control silicon controlled trigger pulse need be that benchmark is regulated with the zero-crossing pulse of electric current, if the inaccurate meeting that current zero-crossing point detects often causes trigger advancce or hysteresis, produce the phenomenon of electric current phase shortage starting failure.

Summary of the invention

The utility model is the current over-zero point detection device in the motor soft starter, this device is used to gather the zero-crossing pulse signal of motor electric current when starting, and the pulse signal that collects is used as synchronizing signal and sends control system to and carry out the given of computing and SCR trigger pulse.

The purpose of this utility model is to have solved electric machine soft starting controller current zero-crossing point to gather inaccurate problem.

The purpose of this utility model is achieved in that a kind of current over-zero point detection device that is used for motor soft starter, form by window comparator circuit unit (1), capacitor resistor unit (2), shaping circuit unit (3) and pulse-width regulated unit (4), it is characterized in that window comparator circuit unit (1) connects capacitor resistor unit (2), capacitor resistor unit (2) connects shaping circuit unit (3), and pulse-width regulated unit (4) connect shaping circuit unit (3) again.Pulse shaping unit forms Schmidt trigger, guarantees the output signal reliability of entire circuit.

The utility model also has other following feature:

Window comparator circuit unit (1) is made up of first voltage comparator and second voltage comparator, and first voltage comparator connects second voltage comparator.

The utility model has solved electric machine soft starting controller current zero-crossing point and has gathered inaccurate problem, makes soft starter can receive accurate zero cross signal, comes the conducting controllable silicon thereby send trigger pulse accurately, makes the starting of motor more reliable.

Description of drawings

Fig. 1 is a motor soft starter current over-zero point detection device circuit diagram,

Fig. 2 is current signal and zero-crossing pulse correspondence principle figure,

Fig. 3 is that motor soft starter current over-zero point detection device connects sketch,

1-window comparator circuit unit, 2-capacitor resistor unit, 3-shaping circuit unit, 4-pulse-width regulated unit.

Embodiment

This device adopts voltage comparator to form window comparator circuit, the AC signal and the given voltage range of input are compared, when input signal total system output high level signal during, output low level signal when input signal is not in the voltage range scope at voltage range.The width of high level is the width that input signal falls into voltage range.The bias voltage maximum of the voltage comparator that this device adopts be 2mv only, and LM393 forms by integrated circuit, and precision is very high, thus can be the window voltage setting very low, detected like this zero crossing just more approaches actual zero crossing.The utility model has also also designed the pulse shaping circuit that is used to eliminate interference and noise at the output terminal of window comparator, by IC1 integrated circuit 74HC4538, resistance R 1, R2 is that 5K-15K ohm, capacitor C 1, C2 are formed for the 0.1-1 microfarad, is used to eliminate the unnecessary zero-crossing pulse that produces in the vibration of window place owing to current signal.Pulse shaping circuit forms Schmidt trigger, guarantees the output signal reliability of entire circuit.The utility model has solved electric machine soft starting controller current zero-crossing point and has gathered inaccurate problem, makes soft starter can receive accurate zero cross signal, comes the conducting controllable silicon thereby send trigger pulse accurately, makes the starting of motor more reliable.

Zero cross detection circuit as shown in Figure 1.When input signal during greater than positive voltage reference and negative voltage benchmark, N1B exports negative level, and N1A exports positive level, and positive negative level is cancelled out each other, and total system is output as 0; When input signal less than positive voltage reference, during greater than the negative voltage benchmark, when promptly signal was between positive and negative benchmark, N1B exported positive level, N1A also exports positive level, total system is output as positive level; When input signal during less than the generating positive and negative voltage benchmark, N1B exports positive level, and N1A exports negative level, the back output 0 of cancelling out each other; When input signal greater than negative level during less than positive level, N1B exports positive level, N1A also exports positive level, total system output positive level, the rest may be inferred, each like this high level (as Fig. 2) of all can exporting when input signal is between the generating positive and negative voltage benchmark.Simultaneously in order to reduce the unnecessary zero cross signal that causes owing to the shake of input signal between positive and negative benchmark, in the output termination of window comparator the shaping circuit formed of integrated circuit (IC) 1, it will can not export zero cross signal when the input end of IC1 has undesired signal or unnecessary pulse signal.The width of R2 and C2 gating pulse wherein.

When motor soft starter is worked, produce alternating current, behind Hall element, produce voltage signal and pass to the current over-zero testing circuit.Electric current whenever falls into once will produce a zero-crossing pulse between reference region, zero-crossing pulse is passed to controller again and carried out computing and send next trigger pulse.

The explanation of Fig. 1 element:

The first voltage comparator N1A	Integrated circuit LM393
The first voltage comparator N1A	Integrated circuit LM393	The first voltage comparator N1B	Integrated circuit LM393
?R1	Resistance	The first voltage comparator N1B	Integrated circuit LM393
?R1	Resistance	?R2	Resistance
?C1	Electric capacity	?R2	Resistance
?C1	Electric capacity	?C2	Electric capacity
?IC1	Integrated circuit 74HC4538	?C2	Electric capacity
?IC1	Integrated circuit 74HC4538	?+V	+ 5V power supply
?-V	-5V power supply	?+V	+ 5V power supply

The first voltage comparator N1A	Integrated circuit LM393
The first voltage comparator N1A	Integrated circuit LM393	?GND	Power supply ground

Each element connected mode among Fig. 1:

5 pin of N1B connect positive voltage reference, and 3 pin of 6 pin and N1A are connected the input end of current signal simultaneously.2 pin of N1A connect the negative voltage benchmark, 8 pin are connected respectively with 4 pin+V and-V, 4 pin of 7 pin, R1, C1 and the IC1 of 1 pin and N1B link to each other.The other pin of R1 and C1 is connected respectively+V and GND.3,5,6,16,13, the 11 pin connection+V of IC1,12 and 8 pin meet GND, series capacitance C2 between 1 pin and 2 pin, 2 pin and+V between resistance in series R2,6 pin are the output of total system.

Claims

1. current over-zero point detection device that is used for motor soft starter, form by window comparator circuit unit (1), capacitor resistor unit (2), shaping circuit unit (3) and pulse-width regulated unit (4), it is characterized in that window comparator circuit unit (1) connects capacitor resistor unit (2), capacitor resistor unit (2) connects shaping circuit unit (3), and pulse-width regulated unit (4) connect shaping circuit unit (3) again.

2. a kind of current over-zero point detection device that is used for motor soft starter according to claim 1, it is characterized in that: described window comparator circuit unit (1) is made up of first voltage comparator and second voltage comparator, and first voltage comparator connects second voltage comparator.