Understanding Solid State Relays controlling 120 vac Vibrators

[Baker in Virginia]

Good Evening ,

I should know more about Solid State Relays . I have
a system with 8) 120 vac Vibrators . These Solid State
Relays have a 4-32 VDC Input . The analog input is reading
24 vdc , but none of these Vibrators will work .

To begin with , what really does the 4-32 VDC mean ? Any
voltage 4 to 32 volt will trigger the Solid State Relay ? There are
Diodes on the wires going out to the Vibrators . I took the wires
off the Solid State Relays , and placed the wires on a 120 VAC terminal
and all 8 Vibrators run. Depending on the 4-32 VDC output from the output
of the PLC , does that determine how much of the 120 vac , pass through to
the Vibrator ? Thanks so much for your help .

 

[robertmee]

Model and manuf of relay?

 

[Baker in Virginia]

Carlo Gavazzi. RM1B23D25 4-32 VDC

Thanks ,

 

[busarider29]

Is this a new system being commissioned or an existing one that was previously working? You say that there are 8 SSRs, and none of them are allowing voltage/current to pass and energize the vibrators? If that is the case, then I have to believe its something else and not anything with the SSRs. Your SSR model is "instant-on". Any voltage in the range of 4-32VDC will make the SSR switch on. Of course like anything else, SSRs can fail, but they typically fail closed, not open. What PLC and output card/module are you using?

 

[danw]

You've connected your vibrators to 120VAC so that the vibrators are running continuously. The purpose of the solid state relay is to switch the vibrator off and on, but you've removed the switching function.


Whatever DC signal is supposed to be present to turn the SSR ON is not working. You need to troubleshoot why there's no DC (+) on terminal A1 (+).

 

[robertmee]

Get your meter...

Meter on VDC, probes on the plus/minus of the relay where the DC connects, what Voltage?

Meter on VAC, red probe on one terminal of relay, black probe on gnd, do you have 120VAC?

When you have DC voltage applied, do you have 120VAC on the other AC terminal also?

If all that checks, then SSR is working fine. If you have VDC but 120VAC only one one terminal then SSR bad. If you have VDC and no 120VAC on either terminal, then your 120VAC supply is missing.

 

[MaxK]

I absolutely agree with robertmee #6: all relay "circuits" need to be measured.

There are Diodes on the wires going out to the Vibrators .

Are you sure that there are diodes in the 120VAC circuits?
I'm not a good electrician, so I have a question for the professionals:
How will the anti-parallel thyristor (its "control system") work if there is a diode in the switched circuit?

 

[JaxGTO]

I have seen before with vibrators that you have to have a diode inline with the signal to create basically half-wave AC, or pulsing DC. Otherwise the vibrator just hums and doesn't move anything.

 

[Baker in Virginia]

Good Morning ,

Thanks for all your helpful comments . Just to answer a few questions....

- This machine and it's present operation as been like this for years, and has
had issues with the Vibrators .

- Yes , each wire going out to the vibrators , have a diode .

- Yes , there is roughly 24 VDC on the input of the Solid State relays .

I plan on digging deeper into this tomorrow morning .

Thanks again ,

 

[lfe]

A coil fed through a diode is not a normal AC load.

The presence of this diode can prevent the thyristors from being fired.

Had vibrators worked before with the same model of solid state relay?

 

[Baker in Virginia]

Yes , they have ran before . So the 120 vac coming from the Solid State Relay
to the vibrators , has a Diode going to the vibrator . I imagine the reason for that is "clipping" the bottom wave , correct ?

 

[MaxK]

Yes , they have ran before . So the 120 vac coming from the Solid State Relay to the vibrators , has a Diode going to the vibrator .

Do I understand correctly that the entire circuit (relays + diodes + vibrators) has already worked in exactly this configuration?

 

[Baker in Virginia]

Yes it has . I'm new here , but they say that it has been a problem. I'm going to dedicate my day tomorrow to dig into it more.

 

[robertmee]

Yes , they have ran before . So the 120 vac coming from the Solid State Relay
to the vibrators , has a Diode going to the vibrator . I imagine the reason for that is "clipping" the bottom wave , correct ?

Is the diode in series or parallel?

 

[lfe]

Yes , they have ran before . So the 120 vac coming from the Solid State Relay
to the vibrators , has a Diode going to the vibrator . I imagine the reason for that is "clipping" the bottom wave , correct ?

With the diode, only the upper or lower half wave conducts and that can alter the proper functioning of the SSR.

You could try connecting a resistive load in parallel with a diode + vibrator, for example a tin soldering iron or an incandescent bulb of about 100W. Maybe then it will work

Also try reversing the cables at the SSR output terminals.

Is the diode in series or parallel?

If it were in parallel something would have burned, at least the fuse.