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    Have a question about solid state relays and their applications? Ask me!

    PeteB

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      Pete Bamburak

       

      Pete Bamburak

      As the Field Applications Sales Engineer for Crydom North America, Pete offers 26 years of expertise and experience in solid state relay use and applications.


       

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        • 1. Re: Have a question about solid state relays and their applications? Ask me!
          kobehua

          To Pete,


          Hi i am a student from UTHM Malaysia currently i am doing a degree electrical and electronic research, so i might want to ask sir technically about solid state relay first is about the Switching Mode of the Solid State Relay. There are 5 types as shown in the Element14. so can Sir practically about all those type of mode in application uses?

           

          Such as:

          1) AC Switch

          2) DC Switch

          3) Non-zero crossing

          4) Random Turn On

          5) Zero Crossing

           

          i don't know which type suitable to my research product Mr Pete, but i prefer a switching mode that are able to response instantly to OFF the AC terminal when detect a low voltage signal on the DC terminal. Please let me know if Mr Pete have any ideas which type of switching mode relevant or suitable to my research...

           

          Thanks and regard,

          Vincent Lee

          2 of 2 people found this helpful
          • 2. Re: Have a question about solid state relays and their applications? Ask me!
            PeteB

            Hello Vincent, and thank you for your question.

             

            I'll do my best to answer it as completely as possible here, but for more detailed explanations you can access anytime, Crydom provides thorough explanations of what solid state relays are, how they're used, the selection of which types to use, how to determine heatsinking requirements, etc., etc., under the "Tech Library" and "Service and Support" heading on our Crydom Website home page, www.crydom.com   Links to the Service and Tech Library are:

             

            http://www.crydom.com/en/Service/Training.shtml

            http://www.crydom.com/en/Tech/Tips.shtml

             

            So to your questions...

             

            #1 and #2 pertain to the 2 general types of SSR's.   Unlike mechanical relays, solid state relays are specificly constructed to switch either AC loads or DC loads.  They cannot switch both.   SSR's that switch AC loads typically use dual power SCR's, (Silicon Controlled Rectifiers), connected inversely and in parallel,  with each SCR switching one side of the AC voltage.   DC switching SSR's utilize Bi-polar power transistors or more commonly power MOSFET devices.   Again, more details on this subject can be obtained through the links provided.

             

            #3, #4, and #5 refer to the switching characteristics available with solid state relays.   The terms "Non-zero crossing"  and "Random turn-on" are interchangeable and mean exactly the same thing.     Since solid state relays are of course, "solid state", and can react in micro seconds if desired unlike mechanical relays,  the exact switching point in the AC waveform where the output turns on can be easily designed into the SSR.     The main advantage of using a zero-crossing turn on SSR is when the load being switched tends to be of a "high inrush" type, usually having a capacitive  characteristic or a tungsten lamp load where the "cold resistance" of a tungsten filament is much lower than its "hot resistance" and would result in a very large current surge for the first few AC cycles.  The turn-on at the zero voltage crossing point lessens that surge substantially.    The zero-cross effect means that if the input signal is applied at any point during the AC output wave other than very close to the zero voltage point of that wave, the output will "wait" to switch on until the AC wave reaches the following zero point.    The "random switching" type SSR means that the output switches on within micro-seconds of the application of the input regardless of where the AC waveform is at that point.   Random turn-on type SSR's are typically recommended for inductive load applications such as motors, coils, etc, due to factors involving the current and voltage phase shift involed,  ( a much deeper subject than can be covered here), along with applications that use the SSR to vary the power levels of AC loads through "phase angle control" such as lamp dimming or resistive heater control.  

             

            The last part of your question regarding a need to "instantly" turn-off your AC output when a low level DC input is received can be covered in two parts.

             

            First, the turn-OFF of either a zero-crossing or random turn-on SSR are both identical.   Since the output uses SCR's, even if an input signal commands a turn-on the SCR that is conducting at that time will NOT stop conducting until the load current is reduced to zero, (for a resistive load that point will be at the zero-voltage point of the AC wave).   Therefore, the turn-off time for an AC output SSR can be almost as long as 1/2 the AC cycle time, (for 50 hz that would be 10msec), or as short as a few micro seconds if the turn-off was received just at the zero-cross point.

             

            The second part of your last question involves your need to turn-off the load when a DC signal is received.  This requires a "normally closed" SSR function (output always on without an input signal,   output will switch off with an input signal, sometimes referred to as a form "B" switch).   Just about 99.99% of the SSR'[s manufactured in the world are of the normally open type.   Fortunately, Crydom covers that 00.01% with a solid state series of relays that includes some normally closed (for "B") versions.   Please look through the datasheet for our S1 series (link below) where you will see that for most of the variations listed a "-B" suffix can be added that designates a normally closed version.

             

            http://www.crydom.com/en/Products/Catalog/s_1.pdf

             

            I hope this "small" dissertation has helped you in your understanding of the Crydom solid state relays.

             

            Thank you again,

            Pete B.

            2 of 2 people found this helpful
            • 3. Re: Have a question about solid state relays and their applications? Ask me!
              PeteB

              Vincent.   I would also like to add that there is a very comprehensive set of "Crydom Solid Statement" paers covering almost every facet of the Crydom SSR's and their application in our "Documents" section here in Element 14.

               

              http://www.element14.com/community/community/suppliers/crydom

               

              It would be very useful for you to take a look at the subjects covered which include our discussion.

               

              Regards,

              Pete B.

              2 of 2 people found this helpful
              • 4. Re: Have a question about solid state relays and their applications? Ask me!
                kobehua

                Sir Pete, thank for the information given above. your guidance is very professional and technical....

                 

                however i would like to ask more questions about the as below:

                 

                Relay Terminals

                Cage Clamp

                Push In

                Surface Mount

                Through Hole

                 

                Contact Configuration

                SPST

                SPST-NC

                SPST-NO

                 

                MSL

                     MSL 2A - 4 weeks

                 

                SVHC

                No SVHC (15-Dec-2010)

                No SVHC (19-Dec-2011)

                No SVHC (20-Jun-2011)

                 

                these are the parameter when choosing the solid state relay property at

                http://my.element14.com/jsp/search/browse.jsp?N=2105+204034&Ntk=gensearch&Ntt=solid+state+relay&Ntx=mode+matchallpartial

                 

                i am not very clear about these parameters when selecting the SSR, so i would like to ask Sir Pete for more simple and technical explaination...sorry for any trouble that i causes to you Sir.

                 

                thank and regard

                Vincent Lee

                1 of 1 people found this helpful
                • 5. Re: Have a question about solid state relays and their applications? Ask me!
                  PeteB

                  Hello Vincent.  Glad to help.

                   

                  The parameter shown as "MSL" refers to "Moisture Sensitivity Level".  Certain solid state components require special attention regarding exposure to ambient atmosphere.  You can refer to the WIkipedia link here that has a decent explanation.

                   

                  http://en.wikipedia.org/wiki/Moisture_Sensitivity_Level

                   

                  The term "SVHC" regards products that meet the "REACH" European Community hazardous material regulations that were effective as of the date shown.  Selection of the "No SVHC (19-Dec-2011)" box will show all the products that have no restrictions for hazardous substances per the latest list published.

                   

                  "Contact Configuration" is simply that.  It allows the selection of the available output contact configurations available for the particular category.  In this case, it appears you've selected "PCB Mount" type relays, and within that category there are only two types available, SPST-NO, (single pole normally open)  and SPST-NC, (single pole normally closed).  The selection of just the SPST selection would show all the SPST products, both NO and NC.

                   

                  The "Relay Terminals" selection just comes down to your preference as to how to connect to or attach wires to the relays.  If you are undecided, the best thing to do would be to examine a couple of datasheets and look at the differences.

                   

                  Pete B.

                  1 of 1 people found this helpful
                  • 6. Re: Have a question about solid state relays and their applications? Ask me!
                    kobehua

                    Mr Pete,

                    ok....thank Mr Pete

                     

                    so what is the different between SPST-NO, (single pole normally open and SPST-NC, (single pole normally closed)? sorry i cant found any relevant of this details on wiki or other sources. and again i would like to ask Mr Pete about this.

                    1 of 1 people found this helpful
                    • 7. Re: Have a question about solid state relays and their applications? Ask me!
                      PeteB

                      Vincent.  

                       

                      The terms SPST-NO and SPST-NC are probably the most basic terms in referring to a switch operation.  "SPST" refers to a "S"ingle "P"ole, (one set of switch contacts that have only one action, ("S"ingle "T"hrow, meaning either open or closed).       NO,   "Normally open"  means just that.  Without an input signal, the contacts are normally "Open".  (In the case of a solid state relay, the output is "OFF").      When an input signal is applied, the contacts then "Close"

                       

                      NC-  :"Normally closed" is the opposite.   Without an input signal, the contacts are "closed".  When an input signal is applied, the contacts move to the "Open" position.

                       

                      There are many references you should be able to find on the internet to diagram and explain this in much detail.  Search for "basic light switch wiring"  or "basic electrical switch wiring".

                       

                      Pete B.

                      1 of 1 people found this helpful
                      • 8. Re: Have a question about solid state relays and their applications? Ask me!
                        kobehua

                        thanks Mr Pete,

                         

                        a very last question....the Load Current of the SSR mean the

                         

                        1)The SSR maximum load current of 12A which is in range 0-12A allow to load?


                        or


                        2)the SSR can allow only 12A current to the load?

                         

                        Regard

                        Vincent Lee

                        1 of 1 people found this helpful
                        • 9. Re: Have a question about solid state relays and their applications? Ask me!
                          PeteB

                          Vincent,

                           

                          The maximum load current rating of the SSR refers to the maximum load current that can be safely handled by the SSR, and is the top of a range.   It can switch loads that vary from the minimum specifiied load current, (also noted on the SSR datasheet), to that maximum.  (Your statement #1).

                           

                          The relay WILL NOT limit the load current, and if a load draws more current than the specified maximum, the SSR could be permanently damaged.

                           

                          Regards,

                          Pete B.

                          1 of 1 people found this helpful
                          • 10. Re: Have a question about solid state relays and their applications? Ask me!
                            ehagerman2

                            What kind of SSR do I need for this application?  Is a 240V output too much to use on 110V device when my input is all 110V, using this device as a the on and off indicator.  SSR NEEDED.bmp

                            1 of 1 people found this helpful
                            • 11. Re: Have a question about solid state relays and their applications? Ask me!
                              PeteB

                              Hello Ellis.   The SSR output on this type of temperature controller will typically provide  a DC signal that is used to drive the input of most any "DC input" solid state relay that can accept a 3 to 32 vdc control signal.    I suggest that you first decide on and select a mounting style, (Panel, Din, PCB), listed under the Element 14 product category "Switches & Relays" / "Solid State Relays", and then use the Filters to show narrow down the input voltage range to "3V DC to 32V DC".     Then you can use the additional filters to sort for your load current and operating, (output voltage) ranges.   ( FYI, PCB mount SSR's usually have lower output current ratings than Panel or Din-mount SSR's. )

                               

                              A note regarding your question about 240 Vac output with a 110 vac load.   SSR outputs can handle a wide range.   For instance a 280 vac rated SSR can handle  loads from 24 to 280 vac.     As long as your load voltage is within the range covered by the particular SSR, it will work.  

                               

                              Another note regards your comment about switching an "on and off" indicator.   If you know the current draw of that indicator it would help you to narrow down the SSR maximum switching current rating needed so your load would be handled without using an un-necessarily high current capacity SSR.   Also keep in mind that SSR's have a "Minimum" load current specification.    Your load needs to draw at least that miminum through the SSR output to switch correctly.

                               

                              Pete B.

                              1 of 1 people found this helpful
                              • 12. Re: Have a question about solid state relays and their applications? Ask me!
                                ehagerman2

                                Thanks for the info Pete.  I will check out the Switches and Relays!

                                1 of 1 people found this helpful
                                • 13. Re: Have a question about solid state relays and their applications? Ask me!
                                  pota

                                  Hi Pete, Can you pl help me with this question.

                                   

                                  I am using SSR rated at 3-32 Vdc control and 3A, 240 V load. I connected one terminal of AC supply to load terminal of SSR and other terminal of SSR to common terminal of voltmeter, and another terminal of power supply to the postive terminal of the voltmeter. When I switch on the supply I get 240 even when there is no control voltage applied (It should read 0V as there is no coontrol voltage). When I apply control voltage of 4.5 Vdc, it does not make any difference. Does this mean that  SSR is not working. I purchased four of these, all behaves same. I dont think all are damaged. Am i going wrong somewhere? Please help. I want to make sure that SSR is working before I connect to the circuit. Is it possible that SSR is damaged while soldering to the PCB.

                                  Kind regards, Noone

                                  1 of 1 people found this helpful
                                  • 14. Re: Have a question about solid state relays and their applications? Ask me!
                                    YT2095

                                    Hi Pete,

                                     

                                    a couple of questions for you, How well so SSRs handle inductive loads? the sort that would typically cause arcing with regular relay contacts.

                                    and 2, how well do they handle RF? for instance if I wanted to make an antanna switcher box for Transmitting, would it be able to pass the RF without causing problems to the relay or creating unwanted harmonics.

                                     

                                    Thanks

                                    1 of 1 people found this helpful
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