advantages & disadvantages in suing between relay & SSR ? thanks

advantages & disadvantages in suing between relay & SSR ?

thanks

munzir said:

... suing between relay & SSR ?

Click to expand...

What means "suing"? No English word.

"Suing" most certainly is an English word. Look up the verb, "to sue." In the non-legal sense, it means to beseech or petition.

As for the question (assuming the desired word was "choosing") , the choice between a relay and SSR is based on many factors. Cost is one of them. Can you be more specific about your use?

John

Electromechanical vs. Solid State Relay Characteristics Comparison
http://relays.te.com/appnotes/app_pdfs/13c3235.pdf

to kak111 - with all my respect I have to disagree with this document from tyco, some figures look strange, maybe because the document points to high power relays or just tyco points to its own production ... i don't know, but I can give controversial opinion :

Examples:

1. sensitive to corrosion, oxidation, contamination - relay yes, ssr no -> this is simply not true, there are hermetically sealed relays, packaged as good as any ssr, but the terminals of both mechanical and solid state relays are sensitive to corrosion, oxidation and contamination ...

2. electrical life expectancy - emr >100k, ssr >100M -> simply not true, there are relays rated to over 1M or 10M ... I don't want even to discuss the conditions that will determine the life expectancy ... but usually this is given in datasheet, so the manufacturer usually gives those figures together with some requirements how to use the relay.

3. normal failure mode - emr open, ssr short -> simply not true, I can show relays that are stack at close, fused and I guess there are ssr that are blown and the failure mode is stack at open, anyway what point does it make to say what is "normal" failure mode - the failure is usually abnormal behaviour of any component

4. normal wear out mechanism for ssr - led ? hmm, what about electro migration ? avalanche effect ? overheat ? esd on gate ?

5. capable of coaxial load switching, i.e. for RF applications - stated that ssr is no, this is simply not true - solid state rf switches exist, analog devices and other companies are making such for decades ... for high power there are pin switches.

I don't want to continue further, just gave those examples to show that in nowadays it is not so simple to say which is best - solid state or mechanical relay, everything depend on application and on the tradeoffs that you are ready to do ...

At the end I want to give some personal experience - I have heart many times from old and experienced guys ( my colleagues ) that relay is better because it is mechanical, solid and will survive harsh environment or use - and I have seen many relays fused, or contact is wear-out so high, so they are useless. In the same time I use ssr and I have no problems at all - even when I switch on/off at maximum load many times ... but I use those ssr only where I am not afraid of the leakage, otherwise I put mechanical relay ... again - everything is a trade off and depends on application

edited : don't want to be offensive, just want to give another point of view. Just hope that munzir will write about his application, so that we can give our best advises

kak111 would you comment on that, what tsvetelin_velkov has mentioned above in its post ?

thanks

Yes I agree that this document points to high power relays and I guess it is published in 2000.
I made some additional comments .....
View attachment EMR_SSR_Comparision.pdf

I found this article, still can't say that it is 100% true ( because it is found on the web site of ssr manufacturer I assume that there is some portion of advertisement ), but let's have a look inside :

link:
SSO Application Notes: Solid State Relays vs. Electromechanical Relays - Solid State Optronics

SSRs vs. EMRs
By the nature of design, one can see the differences between an electromechanical relay and a solid state relay. In an effort to demonstrate inherent advantages of each type of relay, the following characteristics should be examined: Service Life, Reliability, Isolation Voltage, On Resistance, Capacitance and Package Dimensions.

Service Life: Because of solid state technology, the SSR definitely exhibits a longer operational life. Since there are no moving parts to jam, degrade or warp, the life span is virtually infinite.
Reliability: During initial operation, both types of relay will exhibit similar levels of reliability. Over time, however, the solid state relay will gain the edge for the same reasons it has a longer service life, there are no moving parts. Also, bounce free operation increases reliability and ensures consistent load control.
Isolation Voltage: Again, by the characteristics of construction, the solid state relay will almost always exhibit higher input to output isolation voltages than an electromechanical relay. For many telecommunication applications, a minimum of 3750VAC is desired, clearly making the SSR the optimal choice in telecom design.
On Resistance: Electromechanical relays have an On Resistance in the range of 100 milliohms, whereas SSRs have an On Resistance in the range of 10 Ohms. The higher On Resistance of SSRs is due to the nature of the MOSFET. The low On Resistance of the EMR allows for greater load current capability and less signal attenuation.
Output Capacitance: Electromechanical relays typically have an output capacitance of less than 1 picoFarad, whereas SSRs typically have a capacitance of greater than 20 picoFarads. Capacitance becomes an issue in high frequency signals, and EMRs are a better option for HF applications.
Package Dimensions: The internal components of the relays control the overall package dimensions. Because there are mechanical parts (coil, core, arm, contact lever arms, spring mechanism) within the EMR, the package size is limited to the physical dimensions of functional internal components. The SSR on the other hand, is limited to only the size of the semiconductor components, and is clearly capable of being manufactured in a much smaller package.

Why Solid State Relays?
Although there are advantages to using both types of relays, solid state relays are fast becoming the better choice in many applications, especially throughout the telecommunication and microprocessor control industries. The high reliability and long life mean less field failures and better product performance. Low input signal levels are ideal for TTL or CMOS applications, and less power consumption translates to longer batter life in portable devices.

The overwhelming advantages of solid state relays lie in the isolation voltage, package dimensions and multifunction capabilities. These advantages are increasingly becoming apparent in the telecom industry.

Finally, multifunction capabilities place SSRs in a class by themselves. Semiconductor technology has allowed the fabrication of small, multi-purpose telecommunication relays where one device can handle both hook switch and loop current or ring detect functions. Even more complex is a device which combines a 1 Form A relay, Optocoupler, Darlington Transistor, and Bridge Rectifier all within a small, 16 pin SOIC package. These multifunction relays give the design engineer unparalleled flexibility in developing new and innovative fax/modem products.

Cost Issues
In the past, there has been a rather large gap between the price of an electromechanical relay and the price of a solid state relay. For a basic 1 Form A SSR, the price was as high as several dollars more than an EMR. With continual advancement in manufacturing technology, this gap has been reduced dramatically making the advantages of solid state technology accessible to a growing number of design engineers.

Conclusion
The future of solid state relays only looks bright. With further advancement in semiconductor fabrication and manufacturing technology, increased performance and functionality will emerge. Already, MOSFETs are being fabricated with On Resistance values of less than one(1) Ohm. As these devices become more readily available, low On Resistance will no longer be a deciding factor in choosing an EMR over an SSR. As semiconductor components become smaller, package dimensions will also decrease. These same advancements will mean that the price gap between SSRs and EMRs is also going to decrease.


Now let's have a look in electromechanical relay manufacturer :

link:
Pickering Technical Help

Life Expectancy
In typical applications, for example, switching 10 volts at 10 mA, the life of dry reed relays will be in excess of 100 million operations. We can help you to choose the best relay for your application.

Calculate how many operations you require from the relay. If it is operated once a second, 24 hours a day, it is worth noting that there are about 31.5 million seconds in a year. The most common reliability problems are caused by abusive loads. - Read On!

Operate Times
The typical operate time of a dry reed relay is between 250 microseconds and 1 millisecond, depending on switch type.

The Form A (energize to make) types in the small Single-in-Line relays are the fastest, typically 250 microseconds.

The release time is typically one half of the operate time.

The Series 102 is a range of sub-miniature coaxial reed relays for high frequency applications up to 3 GHz.

Two package types are available, both displaying outstanding RF performance in terms of low insertion loss, good isolation and excellent VSWR characteristics in 50 ohms systems.

These relays have good coil drive levels making them ideal for portable applications or where space is at a premium. If an even smaller RF relay is required, look at the Series 109RF or 111 RF.

Solid State Relays

A solid state relay (switch) is a term often used to describe a relay where the path is formed by a semiconductor material (silicon, gallium arsenide). Relays made in this way have advantages and disadvantages compared to mechanical switches (reed relays, EMR's):

Advantages:

Can have high hot switch powers
No wear amount mechanism through frequency use within specification
Faster operation


Disadvantages:

Higher DC path resistance
Higher capacitance, especially on higher current types, which limits BW
Off state has much higher leakage
Lower standoff voltages


There are many types of solid state relays (switches) available but only a few are generally considered suited to test and measurement applications.

CMOS Switches
CMOS switches are implemented by a number of semiconductor companies using variations on their standard CMOS processes. Typically these switches have relatively low operating voltage (+/-22V or lower) and are susceptible to problems when power is applied to the signal pins of the switch while their own power supply voltage is absent. Such conditions can cause the switch to operate incorrectly, produce unexpected loads on the UUT or in some circumstances damage the switch. To be suited for inclusion in a test system CMOS switches should be protected, ideally in a way that produces no load on the UUT when the UUT is powered but the switching system (LXI or PXI) is not.
Some CMOS switches include Fault Protection circuits - as is used in the Pickering Interfaces 40-680. In a Fault Protection switch additional series devices are implemented in the switch which automatically open circuit the signal connection if the UUT voltage rises above the switch power supply voltage, ensuring that in these circumstances the switch does not load the UUT. Provided the voltage from the UUT is constrained to within the protection voltage limits (in the case of 40-680 to greater than +/-40V) the switch is protected and does not load the UUT.
In more recent years CMOS has also been applied to RF switches with some success, using advanced CMOS processes RF switches with greater than 6GHz BW have been implemented. These switches tend to have reduced DC current/voltage handling capability compared to mechanical switches and consequently are best implemented in designs where the DC component is removed by AC coupling capacitors. The 40-880 series RF 6GHz switches use CMOS technology.

MOSFET Switches
MOSFET's can be used to create high current isolated relays. In a typical switch two N type MOSFET's are used with the source connection and drain connection tied together and their drain contacts used as the signal input/output. An isolated differential voltage is applied between the gate and the source direction to turn the MOSFET's on, with no voltage applied the MOSFET's turn off. Two FET's are required to allow the switch to operate from either polarity of signal applied. In the ON state both FET's are on, in the OFF state both FET's are off but one of them will have a parasitic body diode present which prevents it form turning off, the second FET will ensure this conduction is blocked.

SSR Using Two N Channels MOSFET's whose gate bias is derived from a photocell excited by an LED
SSR Using Two N Channels MOSFET's whose gate bias is derived from a photocell excited by an LED


The isolated supply can be implemented in a number of ways, the simplest being the use of an LED illuminating a solar cell to create the voltage needed to turn the relay on. Packaged device are available that integrate the LED, solar cell and FET in a single device, such as that used on the Pickering Interfaces 40-682 MUX and the 40-563 BRIC. For higher current and voltage applications though a discrete design is required, such as that used on the 40-191 ad 40-192 Fault Insertion Switch and its derivatives. The 40-191 and 40-192 offers very high hot switch powers - over 1 kW - without any long term degradation or reliability issues. This is a major advantage for solid state relays of this type, especially when switching power supplies with high inrush currents (the inrush current handling is typical at least three times the continuous rating with no switch degradation) to storage capacitors or trying to simulate intermittent faults in fault insertion applications.

Solid State Relays of this type are very usual, and can be very compact compared to EMR's for high current applications. They do have their compromises though, just like any other switch technology.
As the required voltage rating rises, so does the on resistance of the MOSFET's. Larger MOSFET's have lower on resistance, but they also have higher leakage currents and capacitance which in turn restricts the bandwidth. For power applications though the BW is rarely of great concern since the source impedance must be low (to avoid losses) - the ability to stand high inrush currents is a much more crucial factor.

relay manufacturers usually don't put too much superlatives for their production, because the technology is already well known and the markets are established, for the SSR I think only the big fish is set for sure, but there are many small player which make the future prospects more bright

An electro-magnetic relay has always been known as the least reliable item in electronic or electrical circuits.

Of course there will be exceptions, but that's the traditional wisdom.

how we use relays (their contacts i.e. NO and/or NC) to control the power ?

thanks

munzir said:

how we use relays (their contacts i.e. NO and/or NC) to control the power ?

thanks

Click to expand...

1:- NO means Normally opened contact
2:-NC means Normally closed contact
Moreover previously you inquired about the advantages/disadvantages of the relays vs ssr.
The major advantage of the ssr over relay is having no mechanical contacts,since the mechanical contacts get bounced and sparked which require spark quenching circuits in parallel to the same.Regards

how we use relays (their contacts i.e. NO and/or NC) to control the power ?

thanks

here is a term paper on the SSRs
Technology World: SOLID STATE RELAYS

What about coil & coil voltage for an electromechanical relay ?

How we manage to utilize the PLC output for any load (i.e. for contactor of motor, valve etc) via electromechanical relay ?

how to wire & control an electromechanical relay ?

thanks

SSR is better because it provides complete isolation from higher voltage to lower voltage circuitry, it is more durable, there is no bouncing back of contacts and there are some more advantages of SSR over ordinary relay

Parameters Electromechanical switches Solid state switches
Frequency range from [DC] from kHz
Insertion loss low high
Return loss good good
Repeatability good excellent
Isolation good excellent
Switching speed in ms in ns
Settling time < 15 ms < 1 us
Power handling high low
Video leakage none low
Operating life 5 million cycles infinite
ESD immunity high low
Sensitive to vibration RF power overstress
Size Big compared to SS-switches Small compared to EM switches
System reliability Low High because they have no moving parts or contacts to degrade
Derating constrain Applicable Not Applicable