can't get the SSR to work - need help

i have SSR with 2 terminals for dc control 3-32V and 2 terminals output for AC up to 480V
I connected the output serial to an ac transformer(220V to 110V) so it will close the circuit between the main 220V power to the transformer when i activate the SSR. but what happens is that i activate it firstly the transformer work and then if i disactivate the SSR and try activate again the transformer doesn't work untill i disconnect the main power 220V
does anyone have any idea?

Sounds like a DC offset problem. An AC Solid State Relay is just a triac, they tend to latch "on" under certain circumstances, DC on the line is one thing that will do it. Another is too high of a dv/dt or di/dt on the load, a "snubber" circuit can fix that. What kind of a load is it?

Thank you for your answer, i'll search for some info about snubber" circuits and try to see if it can help me.
The load i'm trying to work with is AC voltage converter 220V to 110V **broken link removed**
the SSR is connected to the power input of the converter

If the transformer is lightly loaded its inductance may be preventing the triac from turning off. A snubber across the load consisting of a resistor in series with a capacitor may solve this problem as described in this tech note from Omron:

**broken link removed**

awright

awright said:

If the transformer is lightly loaded its inductance may be preventing the triac from turning off. A snubber across the load consisting of a resistor in series with a capacitor may solve this problem as described in this tech note from Omron:

**broken link removed**

awright

Click to expand...

the transformer is ver lightly loaded. it has 26W power and i load it only with 3W load consumer.

according to the link above i have connected 100 Ohm res and 0.1u cap in series to the load terminals of the SSR and now the converter is always working.
**broken link removed**

Congratulations, hazico - I think.

First, the diagram and app note recommend the snubber circuit in PARALLEL with the output terminals and the load, not in series. I assume that you wired the snubber as shown in the figure.

Second, I hope you are saying that the SSR is always working properly. "Always working" could be interpreted as always on, which I don't think you mean.

Have fun.

awright

It is always on. sorry if i didn't explain myself properly...
i wired the circuit exactly as the figure above which i found in the link that you gave me.

Try your SSR with a straight resistive load to determine whether it it damaged. If you use an incandescent lamp as a load, be sure it is rated well below the rated current of the SSR because a tungsten filament is a very low resistance when cold and draws high inrush current that could damage the SSR. A hair dryer at low setting might be a good load if it is within the SSR current rating because its element does not change resistance dramatically.

As noted in the Omron tech note, the snubber components would ideally be optimized for the load characteristics. The values given are just typical values that work in many situations. Maybe just not yours. If might have to be adjusted for a 220 volt load.

How are you driving the SSR control input? Any chance that there is some leakage into the input terminals when you want the SSR off? If you are using some semiconductor circuit to drive the SSR control line it's possible that what you think is "OFF" is actually "LOW" but not off. TTL logic would have that characteristic. Can you shunt the control terminals with a resistance high enough to not dissipate too much power from the driver while on, but low enough to pull the input voltage down closer to zero when off.

Try it out with your transformer load but with a switch in series with the control terminals. Maybe not a complete solution, but possibly a good diagnostic technique.

awright

awright said:

Try your SSR with a straight resistive load to determine whether it it damaged. If you use an incandescent lamp as a load, be sure it is rated well below the rated current of the SSR because a tungsten filament is a very low resistance when cold and draws high inrush current that could damage the SSR. A hair dryer at low setting might be a good load if it is within the SSR current rating because its element does not change resistance dramatically.
My SSR can handle up to 25A. i tryed it now with hair dryer, very weird...
the air dryer is always off (turnd on only for a second)... and if i try the transformer its always on.
As noted in the Omron tech note, the snubber components would ideally be optimized for the load characteristics. The values given are just typical values that work in many situations. Maybe just not yours. If might have to be adjusted for a 220 volt load.

How are you driving the SSR control input? Any chance that there is some leakage into the input terminals when you want the SSR off? If you are using some semiconductor circuit to drive the SSR control line it's possible that what you think is "OFF" is actually "LOW" but not off. TTL logic would have that characteristic. Can you shunt the control terminals with a resistance high enough to not dissipate too much power from the driver while on, but low enough to pull the input voltage down closer to zero when off.
I thoght about a leakage from the input so i started to use 9V battery for controlling the SSR. BTW there is a LED on the SSR so i can see that it "works" every time i control it.

Try it out with your transformer load but with a switch in series with the control terminals. Maybe not a complete solution, but possibly a good diagnostic technique.

awright

Click to expand...

..........

What make/model of SSR are you using?

Do you mean that each time you continuously apply 9V to the gate from your battery that the hair dryer goes on for one second, then turns off? Do you mean that it came on only once and will not come on again? If so, the SSR may be burned out. What is the power rating of the hair dryer at the level you used and what is the current rating of the SSR?

Does the LED on the SSR tell you that the output device is on or that a control signal is present? Does the LED intensity change with applied control signal voltage?

The purpose of suggesting powering the hair dryer was to determine that the SSR is functional with a relatively non-reactive load. If I understand your response correctly, it sounds like the SSR is, in fact, defective (or we made it defective).

awright

Put a load on the output of the converter and see if it's still "operating". Your converter is nothing more than a step-down transformer. The snubber circuit, acting as a high-resistance switch in parallel with the SSR output, might be allowing enough current (even with about 32K of Xc at 50 Hz) that you'll measure nearly 120v at the output with a DMM with no load connected. Connect a load and that voltage will die a sudden death.

Dean

awright said:

What make/model of SSR are you using?

Do you mean that each time you continuously apply 9V to the gate from your battery that the hair dryer goes on for one second, then turns off? YES Do you mean that it came on only once and will not come on again? YESIf so, the SSR may be burned out. What is the power rating of the hair dryer at the level you used 230V 2000W and what is the current rating of the SSR? 25A 24-480V

Does the LED on the SSR tell you that the output device is on or that a control signal is present? I don't know Does the LED intensity change with applied control signal voltage? don't think so
The purpose of suggesting powering the hair dryer was to determine that the SSR is functional with a relatively non-reactive load. If I understand your response correctly, it sounds like the SSR is, in fact, defective (or we made it defective).

awright

Click to expand...

Dean Huster said:

Put a load on the output of the converter and see if it's still "operating". Your converter is nothing more than a step-down transformer. The snubber circuit, acting as a high-resistance switch in parallel with the SSR output, might be allowing enough current (even with about 32K of Xc at 50 Hz) that you'll measure nearly 120v at the output with a DMM with no load connected. Connect a load and that voltage will die a sudden death.something strange happen doing it.. main pluge connected with converter and without load and SSR off the converter's led is on, then i plugged the load to the converter and it turned off just like you said but then i turnd on the SSR the converter turnd on and stayed on even when turning off the SSR.

Dean

Click to expand...

I checked resistance on the SSR output terminals (without the cap+resistor) and i got about 1.5M ohm while ON and disconnection while OFF
with the cap&res its about 50K ohm and 47K (ON and OFF).

I never thought using SSR will be so complicated, i thought it's just like using a relay...
Thank you , i appreciate your help.

Measurements of resistance across the SSR output terminals are meaningless due to the diode full bridge and SCR junctions in the path. Measuring voltage across a moderate to full load makes more sense.

Thanks for the link to the data sheet. Would've been beneficial to provide that in your original post. Note that it says, "not for inductive load," however, it then gives a correction factor for permissible inductive loading. The correction factor can become very small as the load approaches a pure inductance, as your lightly loaded transformer may be. The power factor of an ideally loaded transformer can be very high, that is, approaching 1.0, which is equivalent to a pure resistor.

The fact is that both relays and SSRs must be applied with due consideration to the characteristics of the relay and the load. It's just that you can get away with deviating from good practice for a longer time with an electromechanical relay because failure due to misapplication usually takes longer to become evident.

My two questions about powering the hair dryer in my post of 3/6/09 were intended to be mutually exclusive so your yes, yes response confuses me. Nevertheless, if the hair dryer does not stay on for the duration of application of the 9 volt control input, I think your SSR is defective. Be sure that your battery is good and is not itself just applying a pulse of control current, then decaying to an insufficient control voltage.

awright

How about a simple subsitution of a 25 watt light bulb for the converter and see how that works. You'll be miles ahead on the troubleshooting aspect so that you're at least heading in the right direction as to the problem area.

Dean

I can connect a light bulb instead the converter because the converter's output is 110V and i only have my 3Whatt load for 110V (we use 220V here)

awright - about the 9V battery, i think it's good but i'll try today to use 220V to 6VDC transformer for the control.

hazico: It would be sufficient to merely measure battery voltage with a VOM or DVM while using it to apply control voltage to the SSR. If the voltage remains above the minimum specified control voltage of the SSR then the battery is adequate. Seems easier than using an external power supply, but that would also be OK. I'm not doubting that the battery is good - just covering the possibilities before condemning the SSR to the garbage can because if the control voltage is good all evidence indicates a defective SSR.

I don't understand your response to the light bulb suggestion. Surely you have incandescent bulbs for your local utility voltage. Just use one of them directly in series with the output terminals of the SSR. Wattage is not critical. Any incandescent bulb you have laying around will be OK.

Where is "here"? Are SSRs difficult to acquire or expensive "here"?

awright

awright - I just meant that in my country we use 220V so i can't find a bulb for 110V ( i thought tuy wanted me to connect the bulb to the converter ) but if you wantthe bulb to the SSR's output thats not a problem.