SSR fails frequently within a period of time.

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shetsachin

Joined Jul 5, 2017
23
Hi,

For my requirement I'm using phoenix contact SSR 2966595 (24DC/2A) which fails frequently after 15-20 days of usage.Which is operating at 10hz. The SSR input connected to opto isolator & output connected to input of 001 KDD 06100 (4-32VDC/10A) SSR relay. please help me is am doing anything wrong.In below schematic need to be improve?
below is the schematic which give clear picture.
SSR1 2966595 have input internal resistance 3.1K, & SSR 2 have input internal resistance of 2.1K.

upload_2019-5-30_12-40-58.png
Thanks,
 

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You need to place a diode across the solenoid coil to absorb the current when the SSR turns off. You are probably getting a lot of spikes in the 24V power.
I agree with the other posts, this looks like over kill. You could simplify the circuit.
 

eetech00

Joined Jun 8, 2013
3,859
Hi,

For my requirement I'm using phoenix contact SSR 2966595 (24DC/2A) which fails frequently after 15-20 days of usage.Which is operating at 10hz. The SSR input connected to opto isolator & output connected to input of 001 KDD 06100 (4-32VDC/10A) SSR relay. please help me is am doing anything wrong.In below schematic need to be improve?
below is the schematic which give clear picture.
SSR1 2966595 have input internal resistance 3.1K, & SSR 2 have input internal resistance of 2.1K.

View attachment 178519
Thanks,
Hi

You have too many opto’s and may not need a relay. What is the load being driven?
 

Daniel Sala

Joined May 28, 2015
65
Hi,

Missing information. That's a rubbish datasheet by the manufacturer, one to be ashamed of...

Neither the datasheet linked to nor the product page on Phoenix say anything about 3.3k internal resistance as far as I have seen. Where is that? Product page does say that "Input voltage range in reference to UN = 0.8 ... 1.2" and "Typical input current at UN = 7 mA".

Is that 13V on, 0V off measured or where do those numbers come from? Maybe the LED is getting over-stressed and dies quickly as a result - Any chance what's happening is actually (24V - 1.2V = 22.8V)/2200 = 10mA * 864000 (10 times a second, ...24hrs a day (or how long is it actually on?))?

As mentioned, only needs one SSR and one relay. Is this some PLC thing? Why so many SSRs? Why "solenoid Festo" when it looks like a relay? I thought solenoids were two wires.
 

MisterBill2

Joined Jan 23, 2018
18,176
Festo is a well established maker of solenoid valves, I am not aware that they make electrical relays. So it may be that the TS has no symbol for a solenoid valve. Certainly there is no reason to have more than one opto-isolator given the relatively low voltages in this circuit. What would make much more sense would be a power transistor with the solenoid as the collector load, and a diode+ resistor combination across the solenoid coil. Use the same opto to drive the base, but add a series resistor to limit the base current just short of saturation, since that will have the transistor switching much faster. Also, the base drive circuit does not need to have 24 volts as the supply. It does need to be isolated from the control logic, but dropping that voltage down to perhaps 8 or ten volts will reduce the stress on the remaining single opto device.
I would be very interested in reading why there is presently a string of opto devices in the original circuit. That is a real puzzle from where I stand.
 
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