Voltage reduction

[ArlieD]

Hello all this is my first post so of course I have a question.

I have a LED being fed from a vfd controller, it is 120v and 6mA. The problem is my ssr is leaking at 62.2 volts and .062mA yes I have the formula and yes I can figure out what size resister to use (1003) at 4watts. thats not the problem , the problem is how do I make sure that once the relay fires
that I have not reduced the voltage so much that the light does not come on?????

[Al_The_Man]

Explain a bit more what you are trying to do?
Where is the LED being fed from and why?
Al.

[ArlieD]

I have a vfd with outputs for a fault light, this light comes on when the vfd is faulted , the led is slightly on all the time , I am trying to put the light out so to speak, but still be able to have it on at full voltage when/if the drive faults out. We seem to have a large number of brown outs here and the drive faults for undervoltage. I have installed a reset and an led the led will tell the operator that the drive is faulted and he can then reset it.

[Al_The_Man]

It sounds like you are taking a SSR off a high voltage output?
The majority of VFD's I have come across usually have a choice of N.O. or N.C. contact closure of the alarm output.
Some have low voltage open collector output, configurable.
This contact closure is the prefered way.
What make of VFD? is there an on line manual that shows where you are taking this output from?
Al.

[ArlieD]

it is a A/B smc flex 150Ft08NBD I am taking the reset from terminal 15 configured to clear fault, the led comes from terminals 31 and 32 which is aux option # 3 and configured for "Fault" in its n/o state. I believe this is a low voltage open collecter output and it is configurable. it just leaks .... if it helps the light is a 800T-Qh10R 120 volts full voltage LED

[ArlieD]

unfortunatly my day is over I would really like to continue this but don't want to keep you hanging so I will check email at home if you reply other wise I thank you for y our time and I will check in the am.

[Al_The_Man]

If you are using a low voltage collector output, how are you using a 120v led?
I will see if I can look up the manual in the mean time.
Al.

[Al_The_Man]

If this is the correct unit
http://literature.rockwellautomation...m051_-en-p.pdf
This appears to be a soft starter?
The outputs on 31 32 look to be contact closure, so there should be no leakage.
You could confirm it with a meter on ohms range maybe.
Al.

[bharbour]

Originally Posted by ArlieD Hello all this is my first post so of course I have a question. I have a LED being fed from a vfd controller, it is 120v and 6mA. The problem is my ssr is leaking at 62.2 volts and .062mA yes I have the formula and yes I can figure out what size resister to use (1003) at 4watts. thats not the problem , the problem is how do I make sure that once the relay fires that I have not reduced the voltage so much that the light does not come on?????

Hi,
If I read your post correctly, you are switching a solid state relay from the VFD outputs and the solid state relay output is leaking a little.

That leakage is probably unavoidable - there is an RC snubber network in most AC output solid state relays that prevents noise triggered turn ons and the snubber leaks a little bit. Could you replace the LED on the relay output with an incandescent bulb that takes more current to light up?

BobH

[ArlieD]

Yes Al it is a soft start, and I am sure it should not leak but it does. On 31 I have 120v , on 32 is the wire to the lamp, the second terminal on the light is the N.

Bob ,

using a incandesant lamp is my last resort, all other lamps on this unit are led so am trying to keep them the same.

Thanks alot for all the help folks

[Al_The_Man]

The PDF definitely shows contact closure, are you sure the contacts are open in the non-alarm condition?
Measure the continuity 31 to 32 with a meter with no power to the unit and then when it is in operation, remove the power first.
BTW, are you using 120vAC or DC, if AC it should be a LED that is conditioned for AC use, you can exceed the reverse voltage rating if an ordinary LED with resistor.
In this case a series rectifier is needed.
Al.

[ArlieD]

absolutly postive the contacts are open with no power.

The Led works as its supposed to when there is a fault it comes on at full power. When contacts are open there is still 62.2v across the terminals of the LED at .062mA so the light remains very dimley lit. I can size a resister to drain the voltage but want to be sure I am not reducing it by too much so that when the contacts close the light will still come on but that the residual voltage is gone and the led will be out.

The Led is rated for 120vac full voltage and yes I am using 120vac