【導讀】year.trapeziumpicture.position.

　　

【正文】 one kind of digital operation and the operation control device. PLC as the traditional relay39。s substitution product, widely applies in industrial control each domain. Because PLC may use the software to change the controlled process, and has the volume to be small, the assembly is flexible, the programming is simple, antijamming ability is strong and the reliable higher characteristic, is suitable specially under the wicked poor environment moves. When carries on the control using the frequency changer constitution automatic control system, in many situations is uses PLC and the frequency changer coordinates to use, for example my factory two catalysis automatic easy systems. PLC may provide the control signal and the instruction makeandbreak signal. A PLC system is posed of three parts, namely central processing element, input output module and programming unit. This article introduced the frequency changer and PLC carry on when the coordination must pay attention item. Foreign Language Translation 8 1. switch order signal input In frequency changer39。s input signal including to running statuses and so on movement/stop, clockwise/reverse, fine motion carries on the operation the switch mand signal. The frequency changer usually or has the tip switch characteristic primary device using the tip (for example transistor) with PLC) connected, obtains the running status instruction, as shown in Figure 1. When use tip, brings the misoperation frequently because of the bad contact。 Uses when the transistor carries on the connection, then must consider factors and so on transistor39。s voltage, current capacity, guarantee system39。s reliability. When designs frequency changer39。s input signal electric circuit should also pay attention, when the input signal electric circuit connection not at that time sometimes also will create frequency changer39。s misoperation. For example, when the input signal electric circuit uses relay and so on perceptual the loads, the relay make and break produces the surge current brings the noise has the possibility to cause frequency changer39。s misoperation, should avoid as far as possible. Figure 2 has given correct and the wrong wiring example with Figure 3. When the entry switch signal enters the frequency changer, sometimes will have the external power supply and the frequency changer control supply (DC24V) between crosstalk. The correct connection uses the PLC power source, exterior transistor39。s collecting electrode after diode pipe joint to PLC. As shown in Figure 4. 2. value signal input Input signal against disturbance39。s connection in the frequency changer also has some values (for example frequency, voltage and so on) the mand signal input, may divide into the digital input and the analog input two kinds. The digital input uses on the frequency changer kneading board39。s keyboard operation and the serial interface much assigns。 The analog input assigns through the binding clamp by exterior, usually through 0~10V/5V voltage signal or 0/4~20mA electric current signal input. As a result of interface circuit because of input signal, but different, must therefore choose PLC according to frequency changer39。s input impedance the output module. Figure 5 is between PLC and frequency changer39。s signal connection diagram. When the frequency changer and the PLC voltage signal scope is different, like frequency changer39。s input signal is 0~10V, but the PLC output voltage signal scope is time 0~5V。 Or the PLC one side39。s output signal voltage range is 0~10V, but frequency changer39。s input voltage signal scope is time 0~5V, as a result of factor and so on frequency changer and transistor39。s permission voltage, electric current limits, needs the series the way turning on limiting resistor and the differential pressure way, guarantees carries on when the make and break does not surpass PLC and the frequency changer corresponding capacity. In addition, when segment should also pay attention the wiring separates, guaranteed that main circuit one side the noise does not pass to the control circuit. Usually frequency changer also through binding clamp to the exterior output corresponding monitor simulated signal. Electrical signal39。s scope usually is 0~10V/5V and the 0/4~20mA electric current signal. Regardless of which kind of situation, should pay attention: The PLC one side39。s input impedance39。s size needs in the guarantee circuit the voltage and the electric current do not surpass electric circuit39。s permissible value, guarantee system39。s reliability and reduced error. Moreover, because these observation system39。s position is not mutually same, has not the Foreign Language Translation 9 clear place to the factory consultation. Moreover, when uses PLC carries on the sequential control, because CPU carries on the data processing to require the time, has certain time delay, therefore when precise control should give to consider. Because the frequency changer will have the strong electromagic interference in the movement, to guarantee PLC not, because the frequency changer main circuit circuit breaker and the switch ponent and so on will produce the noise will present the breakdown, will connect the frequency changer and PLC when should pay attention to the following several points: (1) should carries on the earth to PLC itself according to the stipulation wiring standard and the earth condition, moreover should pay attention avoids mon meeting the grounding with the frequency changer use, and in earth time causes the two to separate as far as possible. (2), when the power source condition is not too good, should turns on the noise filter in the PLC power source module and on the input/output module power line and reduces the transformer which the noise uses and so on, moreover, if has the necessity, should also take the corres