Abstract: Introduction take the P87LPC764 monolithic integrated circuit as core time delay leakage relay design proposal. This plan may realize under the fixed working current and 5 time of fixed working current for the user choice the different time-lag action time, and has switches on the hypothesis selection function again. Has solved the delay time which the former tradition discrete component brings to the divergence and does not realize greatly malpractice.
Key word: Delay time leakage relay monolithic integrated circuit design
1 introduction
Leaks the relay is one kind may after being protected the line leakage electric current achieves the setting value (fixed working current IΔ) shuts off is protected the line electric power supply’s protective device. The leakage signal’s examination completes by zero foreword current transformer, it may examine is protected line’s leakage electric current to transform a millivolt level the alternating voltage signal, again the proceed signal rectification, the enlargement and the filter obtain a DC voltage, then the coordination corresponding control circuit actuates to carry out the return route, realizes the cut-off protection line electric power supply’s control goal. Simple realizes the process is the signal detection -> filter -> second-level enlargement -> control circuit -> actuation carries out the return route -> cut-off to protect the line power source.
This article gives the time delay leakage relay solution is substitutes for traditional using the P87LPC764 monolithic integrated circuit constitution control circuit the electric circuit, this electric circuit may realize the different time-lag action time and other related functions under the different IΔ condition.
2 relay’s functions
Actuates the request according to the leakage protection standard and the time delay leakage relay, this protection attire may realize the following function:
(1) the user may choose 3 grade of fixed working current (to record separately for IΔ1, IΔ2, IΔ3), is protected in the use by the user basis line’s actual state to decide. Generally may establish IΔ1<IΔ2<IΔ3.
(2) under each kind of fixed working current (in 1 time of situation) is equipped with 3 grade of time-lag action time T1a, T1b, T1c (to establish T1a<T1b<T1c), is not difficult to see, these 3 grade of fixed working current must differentiate 9 kind of time-lag action situation. The time-lag action time is refers to the leakage electric current which the electric circuit examines to surpass the fixed working current to the electric circuit to carry out the return route movement and to shut off is protected the line power source’s time.
(3) with the first point correspondence, under 5 time of fixed working current, these 3 grades of electric currents may record separately for 5IΔ1, 5IΔ2, 5IΔ3, the corresponding 3 grade of time-lag action time is T2a, T2b, T2c, similarly establishes T2a<Tab<T2c. Obviously the working current is bigger, the corresponding time-lag action time is smaller, namely T2a<T1a, T2b<T1b, T2c<T1c.
(4) retains in the electric circuit switches on the function again. If chooses this function, when after the protective device movement and shuts off protects the line power source, after the time delay T3 time self-recovery power supply. Otherwise, the equipment must manual regain and return to the original state.
(5) acts according to the leakage movement essential requirements, when after choosing the strip function, the equipment may after the T3 delay time self-recovery, but this time, if examines the leakage signal still surpassed the installment hypothesis the fixed working current (to be possible to be called “two leakage”), in software after time delay T3 follows closely is establishing T4 (T4<<T3) the delay time, namely should have when T4 and surpasses the installment hypothesis the fixed working current, the installment is at the locking condition, must manual restore turns round and returns to the original state; If before the T4 delay time arrives at “two leakage” to relieve or “two leakage” itself does not exist, will not cause the equipment to be at the locking condition. Thus, when design must consider “two leakage” the possibility, avoids switching on again automatically blindly.
3 P87LPC764 synopses
P87LPC764 is 51 essences which, the advanced version monolithic integrated circuit Philips Corporation promotes, the running rate for standard 80C51 molding machine’s 2 times, the rich nimble port definition, contains two precise simulation quantity comparator is selects this model the reason. This monolithic integrated circuit’s major function is as follows:
· the running rate is quick;
· the program memory is 4KB OTP (a programming), 32B user code area;
· 2 16 fixed time/counters;
· 2 precise simulation quantity comparator;
· programmable I/O mouth output pattern;
· 20mA mouth line driving force.
Figure 2
4 hardware circuits
4.1 signal detections and amplifying circuit
Shown in Figure 1 is leaks in the protective device the signal detection and the enlargement part local circuit. This equipment to leaks the electric current the examination to complete with a zero foreword current transformer, by will examine is protected line’s leakage electric current to transform a millivolt level the alternating voltage signal. The linear circuit rectification which constitutes by the operational amplifier enlarges again, through to the zero second-level enlargement, obtains DC voltage U20. Obviously, through to zero foreword current transformer and the corresponding circuit value’s hypothesis, may cause U20 the electric current which leaks in proportion to in a section of leakage electric current’s scope. Thus, to leaks the electric current signal processing to transform in the electric circuit as to U20 processing. Front mentioned that the user may choose, 3 kind of fixed working current, in fact is through adjusts R28, R29, R30 in the electric circuit the U20 installation in 3 kind of different voltages, and with three chooses switch S2A (to provide for user) realizes, each time only then one kind (must have one kind) to choose; Under the fixed working current T1a, T1b, under the T1c time’s hypothesis and 5 time of fixed working current T2a, T2b, the T2c time’s hypothesis through three chooses a switch S3A judgment, similarly each time only then one kind (must have one kind) to choose; Switches on again selects chooses switch S1 to carry on the hypothesis only, concrete electric circuit as shown in Figure 2.
May establish reference potential VREF in the P87LPC764 16 foot external connection resistance voltage divider, may understand the user choice 3 kind of different fixed working current corresponds U20 is different, 
but reference potential VREF only then one kind of standard, this standard, once establishes cannot change, therefore the S2A function is comes the U20 signal through switch’s guidance and potentiometer’s differential pressure different value U20 to adjust the appropriate size, then carries on the comparison with hypothesis reference potential VREF.
4.2 P87LPC764 peripheral circuits
Figure 2 is the P87LPC764 peripheral circuit part, 16 feet are the VREF voltage suppose the fixed end, the reference may obtain VREF=2V according to the chart. 12 foot P1.0 uses in switching on the judgment again, the user may the strobe unit whether to carry out switches on again, P1.0 is 0 when the installment has switches on the function again; P1.1, P1.2, P1.3 use under the fixed working current T1a, T1b, under the T1c time and 5 time of fixed working current T2a, T2b, the T2c judgment and the choice. After second-level enlargement’s U20, a group delivers to the comparator CIN1A input end directly (17 feet), other group delivers to the comparator CIN2A input end through the resistance voltage divider (19 feet), by uses in inputting under the fixed working current separately U20 and under 5 time of fixed working current U20, P0.0 actuates in executive circuit’s relay, the original state hypothesis is 0 (low level, relay attracts gathers), then causes the relay its connection in the following executive circuit to be at attracts gathers the condition, the coordinate exchange contact device maintenance is protected line’s power supply.
5 software designs
The software design mainly revolves under the different condition the delay time hypothesis to carry on, first judges the comparator 1 and the comparator 2 outputs by determined that the current leakage electric current the size, may have three kind of situations specifically: First, is smaller than the current hypothesis fixed working current; Second, is bigger than the current hypothesis the fixed working current but is smaller than 5 time of fixed working current; Third, is bigger than 5 time of fixed working current, these may through judges the comparator 1 and the comparator 2 lose the control in the software. And may according to P1.0, P1.1, P1.2, the P1.3 condition decide whether to switch on and the different operating time again actually. Its procedure flow as shown in Figure 3.
6 concluding remark
Because must differentiate many kinds of delay times, thus uses the monolithic integrated circuit to realize the plan, overcame the tradition discrete component to bring to the divergence and was not greatly easy the malpractice which controlled. The P87LPC764 content voltage comparator, may control the fixed working current and under 5 time of volume working current operating time very conveniently. In the software compilation, the delay time mainly “fixed time realizes by the software time delay and the timer”, completes many kinds of delay times using the transmission different variable’s way the control, the fact proved that this is soft good realizes the plan.
