Peng Jianliu leaps (Guizhou industrial university)

Abstract: Elaborated the solid state relay principle, the structure, the characteristic and the AC-DC solid state relay applicable scope, and aims at the exchange solid state relay, proposed acted according to its several essential parameters to come the reasonable choice solid state relay the method, to apply the electric circuit some questions which needed to pay attention in the design as well as has produced correspondingly the connection electric circuit which refuted with the computer meets.

Key word: Solid state relay; Applicable scope; Essential parameter; Using electric circuit

The solid state relay (SOLIDSTATE RELAYS), Jan wrote "SSR", is one kind completely the new non- electronic contact switch component which is composed by the solid state electronic component, it uses the electronic component (for example semiconductor device and so on switch triode, bidirectional silicon-controlled rectifier) the switch characteristic, may achieve sparkless puts through the goal without the electronic contact which and interrupts a circuit, therefore is called "the non- electronic contact switch", it is published to the 70's, as a result of its non- electronic contact operational factor, causes it obtains day by day Guang Fan's application in many domains electric control and the computer control aspect.

First, solid state relay principle and structure

SSR may divide into according to the use situation hands over the flow pattern and the direct current two big kinds, they separately make the load on the exchange or the direct-current power supply the switch, cannot mix uses.

Chart 1

Under take exchange SSR as regularly explained its principle of work, chart 1 is its principle of work diagram, chart 1 the center part (1) - (4) constitution exchanges the SSR main body, looked from the whole, SSR only has two input ends (A and B) and two out-ports (C and D), is one kind of four pole component. When work so long as on A, B adds on the certain control signal, may control C, between the D beginnings and ends "passes" and "breaks", realization "switch" the function, coupled circuit function is A, the B end input control signal provides between an input/out-port the channel, but separates in SSR on the electricity between the input end and the out-port (electricity) relates, prevented the out-port to the input end the influence, the part which the coupled circuit uses is "the optical coupler", It act keenly, the speed of response is high, insulation between the input/out-port (pressure resistance) and so on rises; Because the input end load is the light emitter diode, this makes SSR the input end to be very easy to achieve matches with the input signal level, in the use may directly with the computer output connection docking, namely receives "1" and "0" the logical level control. Triggers the electric circuit the function will be produces conforms with the request the trigger pip, actuates the switching circuit (4) work, but because switching circuit when does not add the special control circuit, will have the radio-frequency interference and so on pollutes the electrical network by the higher harmonic or the peak, for this ad hoc "zero control circuit". So-called "zero" is refers, when joins the control signal, alternating voltage zero hour, SSR namely for passing condition; But after when the separation control signal, SSR must wait for the alternating current the half period with the negative half period junction 界点 (zero electric potential), SSR only then for breaking condition. This kind of design can prevent the higher harmonic the disturbance and to the electrical network pollution. The absorbing circuit is for prevented transmits the peak, the surge from the power source (voltage), generally is uses "R-C" which (even misoperation) designs to the switch component bidirectional silicon-controlled rectifier tube impact and the disturbance the series absorbing circuit or the non-ohmic resistor (presses sensitive resistor). Chart 2 is one kind of typical exchange SSR electricity schematic diagram.

Chart 2

Chart 3

Direct current SSR and exchange SSR compares, has not had the zero control circuit, also does not need to establish the absorbing circuit, the switch component generally uses the high efficiency switch triode, other principles of work are same. But, direct current SSR when use should pay attention: (1) When load for perceptual load, if the direct current solenoid valve or the electro-magnet, should in the load beginnings and ends parallel diode, polar like chart 3 show, the diode electric current should be equal to the operating current, the voltage should be bigger than the working voltage 4 times. (2) When SSR work should approach as far as possible it the load, its output lead wire should satisfy the load current the need. (3) Uses the power source to be after the exchange falls presses the rectification obtained, its filter electrolysis electric capacity should enough be big.

Chart 4 has produced several kind of homes, outside the common SSR contour.

Chart 4

Second, solid state relay characteristic

SSR successfully has realized the weak signal (Vsr) to the strong electricity (out-port load voltage) control. As a result of the optical coupler application, causes extremely lowly to control the power which the signal cabin needs (approximately ten milliwatts to be possible normal work), moreover Vsr needs the operate level and TTL, HTL, CMOS and so on the commonly used integrated circuit is compatible, may realize the direct connection. This causes SSR at aspect and so on numerical control and automatic control equipment obtains the widespread application. May substitute for the tradition in the suitable degree "the coil - reed electronic contact type" the relay (abbreviation "MER").

SSR because is the entire solid state electronic component composition, compares with MER, it does not have the mechanical part which any may move, in the work also not to have any mechanical movement; SSR "passes" and "breaks" the switch function by the electric circuit active status transformation realization, does not have 电接�?the spot, therefore it has the merit which a series of MER does not have, namely works high reliable, the long life (has material to indicate SSR the switch number of times may reach 108-109 time, general MER 106 is higher than several hundred times); Non- movement noise; 耐振 bears the machinery impact; Installs the position unlimitedly; Very easily fills with the insulation waterproofing material seals makes the entire seal form, moreover has the good moisture-proof mildewproof anticorrosion performance; Is guarding against explosions and prevented the ozone pollution aspect the performance extremely is also good. These characteristics cause SSR to be possible in military (for example flight vehicle, artillery, ships, vehicle to carry armament system), chemical, mine shaft mining coal and in each industry civil electrically controlled equipment application give full play, have surmounted MER the technical superiority.

Exchange SSR because uses zero to trigger the technology, thus may cause the SSR security to use on the computer output connection, does not need for to use a series of on the connection to the computer disturbance which MER produces but the worry.

In addition, SSR also has can withstand may reach nominal current ten time of about in the value the surge current characteristic.

Table 1

Parameter name (unit)
Parameter value

Smallest
Model
Biggest

Input end
Direct current control voltage (V)
3.2

14

Input current (mA)

20


Switch (V)
3.2



Shuts off the voltage (V)


1.5

Counter- 极向 protection voltage (V)


15

Dielectric resistance (Omega)
109



Medium pressure resistance (V)
1,500



Out-port
Fixed output voltage (V)
25

250

Fixed output current (A)


10

Surge current (A)


100

Crosses the zero potential (V)


±15

Output pressure drop (V)


2.0

The output leaks the electric current (mA)


10

Meets between the circular telegram (mS)


10

Shuts off the time (mS)


10

Operating frequency (Hz)
47

70

Power loss (W)

1.5


Shuts off dV/dt (V/ mu s)

200


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110

Operating temperature (�?
-20

+80

Third, the main parameter with selects

The power solid state relay characteristic parameter including the input and the output parameter, under passes the relay main plant production take the Beijing branch the GX-10F relay as an example, lists the input, the output parameter, for details sees table 1, according to the input voltage parameter value size, may determine the working voltage size. When uses logical level control and so on the TTL or CMOS, best uses has the enough belt to carry the ability the low level actuation, and causes "0" the level to be lower than 0.8 as far as possible V. If works under the noise very strong environment, cannot select passes, breaks the voltage value phase difference small product, essential selects passes, breaks the voltage value phase difference big product, (for example splices passes voltage is 8 V or 12 V product) cannot create the control like this because of the noise jamming to malfunction.

The output parameter project are more, presently to main several parameters explanation as follows:

1st, fixed input voltage

It is assigns the stable state anti- load biggest permission voltage which under the condition can withstand 有效�? If is controlled the load right and wrong stable state or non- anti-, the essential consideration chooses the product whether can withstand time the active status or the condition change (cold hot transformation, calmly moves the biggest synthesis voltage which transformation, induced e m f, transient state peak voltage, change cycle and so on) produces. When for example load for perception, chooses the fixed output voltage to have to be bigger than two time of supply voltages value, moreover chooses the product to block (penetrates) the voltage to be supposed to be higher than the load supply voltage peak value two times. If for exchanges 220V, in the general low power non- anti- load situation in the supply voltage, suggested selects the rated voltage is the 400V - 600V SSR product; But regarding frequent start single-phase or three-phase electrical machinery load, suggested selects the rated voltage is the 660V - 800V SSR product.

2nd, fixed output current and surge current

The fixed output current is refers in assigns the electric current which under the condition (ambient temperature, rated voltage, power factor, whether there is radiator and so on) can withstand to be biggest 有效�? The general production factory all raises heating to fall the volume curve. If the ambient temperature rise, should do according to the curve falls the volume use.

The surge current is refers in assigns (time which under the condition room temperature, rated voltage, nominal current and continues and so on) not to be able to create the biggest non- duplicated peak value electric current which the irremediable defect permits. Exchanges the relay surge current for nominal current 5-10 time (a cycle), direct current product for nominal current 1.5-5 times (a second). When selection, if the load for stable state anti-, SSR may the sum total or falls the volume 10% use. Regarding the electric heater, the contact device and so on, initial put through the surge current which instantaneous appears to be possible to reach 3 time of steady currents, therefore, SSR falls the volume 20%-30% use. Regarding Bai Zhideng a kind of load, SSR should according to fall the volume 50% use, and also should add on the suitable protection circuit. Regarding the transformer load, chooses the product the nominal current to have to be higher than the load operating current two times. Regarding the load is the asynchronous machine, chooses SSR the fixed magnitude of current to be supposed for electrical machinery revolution electric current 2 - 4 times, the SSR surge magnitude of current to be supposed for nominal current 10 times.

The solid state relay is very strong to the temperature sensitivity, after the operating temperature surpasses the nominal value, must fall hot or the sur- radiator, for example the nominal current is 10A JGX - the 10F product, does not add when the radiator the permission operating current only has 10A.

Fourth, applies the electric circuit

1st, basic unit electric circuit

Like attempts 5a to show for the stable anti- load, in order to prevent the input voltage 超过�?definite value, must establish limiting resistor Rx; When load for unstable qualitative load or perceptual load, also should attach a transient state suppression electric circuit in the output circuit, like attempts 5b to show, the goal protects the solid state relay. The usual measure is installs the RC absorbing circuit in the relay out-port (for example: R=150 Omega, C=0.5 mu F or R=39 Omega, C=0.1 mu F), it may the effective suppression add to relay transient voltage and voltage index climbing rate dv/dt. When designs the electric circuit, suggested the user basis load the related parameter and the environmental condition, earnestly calculate and experiments the RC return route to choose the value. Another commonly used measure is turns on in the relay out-port has the specific clamp voltage the voltage control component, if the bidirectional zener diode or presses the sensitive resistance (MOV). Presses the sensitive resistance magnitude of current to be supposed to press down the type computation:

Imov= (Vmax-Vmov) /ZS

ZS is sum of the loaded impedance, the source impedance as well as the line impedance, Vmax, Vmov respectively be the highest transient voltage, the pressure sensitive resistance of of nominal voltage, regarding conventional 220V and the 380V alternating current supply, the recommendation pressure sensitive resistance nominal voltage value respectively is 440-470V and 760-810V.

In exchange perceptual load parallel RC electric circuit or electric capacity, also may suppress adds to SSR out-port transient voltage and the voltage index climbing rate.

But tests indicated, RC absorbing circuit, specially parallel in SSR out-port RC absorbing circuit, if combines improper with the perceptual load, is easy to cause the vibration, the electricity or the relay cuts when the load power source, enlarges the relay out-port the transient voltage peak value, increases possibility which the SSR misleading passes, therefore, to concrete should first carry on the experiment using the electric circuit, selects the appropriate RC parameter, even sometimes does not need the RC absorbing circuit to be more advantageous.

The surge current causes which regarding the accommodating load may use the perceptual part suppression, like introduces the magnetism interference rejection unit, the impedance coil in the electric circuit and so on, limits the fast rise the peak value electric current.

Moreover, if the out-port electric current rise rate of change (di/dt) is very big, may connect in the out-port to have the high magnetic conductivity to soften the magnetic core the inductor to perform to limit.

Chart 5

The usual SSR design is "often opens" the condition, when namely non- control signal input, the out-port is leads the way, but frequently needs in the automation control device "often to shut" type SSR, by now might meet group of simple electric circuits outside the input end, like attempted 5c to show, by now namely for often 闭式 SSR.

2nd, multi-purpose control circuit

Attempts 6a is the multi- groups output circuit, when the input is "0", triode BG closure, SSR1, SSR2, SSR3 input end non- input voltage, respective out-port separation; When the input is "1", triode BG leads passes, SSR1, SSR2, the SSR3 input end has the input voltage, respective out-port puts through, thus had achieved controls many out-ports "passes", "breaks" the goal by an input port.

Attempts 6b is the single tool double throw control circuit, when the input is "0", the triode BG closure, the SSR1 input end non- input voltage, the out-port separation, this time A voltage adds to SSR2 the input to carry (UA-UDW to be supposed to cause the SSR2 out-port reliably to put through), the SSR2 out-port puts through; When the input is "1", triode BG leads passes, the SSR1 input end has the input voltage, the out-port puts through, this time A although 有电�? but the UA-UDW voltage value has not been able to cause SSR2 the out-port to put through is at the separation condition, thus has achieved "the single tool double throw control circuit" function (attention: When choice zener diode DW constant voltage value, should guarantee leads SSR1 which passes "+" the end voltage not to be able to cause SSR2 to lead passes, simultaneously must give dual attention to the SSR1 closure time "+" the end electricity pressure energy causes SSR2 to lead passes).

Chart 6

3rd, the computer control electrical machinery is reversing connection and actuation electric circuit

Chart 7 the computer control single phase AC electrical machinery is reversing connection and actuation electric circuit, when reverse control between, is reversing to stagnate the time to be supposed to be bigger than alternating current supply 1.5 cycles ("drop electric circuit to complete with along time delay"), in order to avoid commutates too quickly creates the space to short-circuit. The electric circuit relaying electric appliance must select the breakdown voltage to be higher than 600 V and the rated voltage is 380 V above exchange solid state relay.

Chart 7 the computer control single phase AC electrical machinery is reversing connection and actuation electric circuit

When limit the electrical machinery commutates the capacitor discharging current, should in various return routes sur- limiting resistor Rx, its resistance number and the power may press down the type computation:

Rx=0.2×VP/IR (Omega), P=Im2Rx

Among: VP - power source peak voltage (V); IR - solid state relay nominal current (A); Im - electrical machinery revolution electric current (A); P - limiting resistor power (W)

Chart 8 the computer control three phase ac electrical machinery is reversing connection and actuation electric circuit

Chart 8 the computer control three phase ac electrical machinery is reversing the connection and the actuation electric circuit, in the chart have used 4 NAND gates, with two signal channels distinction control motor starting, stops with the clockwise, the reverse. When change electric motor rotation direction, produces the command signal the order to be supposed to be "stops - the reverse - starting" or "stops - the clockwise - starting". The delay circuit smallest time delay is not smaller than 1.5 alternating current supply cycle. RD1, RD2, RD3 are the fuse. When the electrical machinery permits, may turn on the limiting resistor in the R1-R4 position, prevented when 10,012 spaces wilfully two relays by mistake put through, the limit produces the half period space short-circuit current does not surpass the surge current which the relay can withstand, thus avoids burning down accident and so on relay, guarantees the security; When the side effect is the normal work resistance general has the pressure drop and the power loss. This electric circuit suggested uses the rated voltage is 660 V or the higher SSR product.

Fifth, concluding remark

States from front may see SSR the performance and the electromagnetic type relay compare has very many superiority, is specially easy to realize the computer programming control, therefore conveniently causes the control the realization, to be nimble. But it also has some weakness, for example: Leads passes the resistance (several Omega - several dozens Omega), the passing condition pressure drop (is smaller than 2 V), breaking condition leaks the electric current (5 - 10mA) and so on the existence, is easy to give off heat the damage; When closure has the leakage resistance, cannot cause the electric circuit completely to separate; Easily the temperature and the radiation influence, the stability is bad; Sensitivity high, is easy to have the misoperation; In needs in the control circuit which the interconnection, mutually locks, protection circuit additionally building, causes the cost rise, the volume to increase. Therefore, has regarding SSR the unique performance, must the correct understanding and the discrete use, the side can display its unique performance, and guarantees the SSR non- breakdown the work.