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'[EE]: UPS PROBLEM - HELP - MORE INFO'
2007\04\10@100514 by Carl Denk

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Just to summarize symptom: Relay drops out, switching PLC from 120VAC >
12 VDC switching supply to 2 lead acid batteries connected with diodes
to relay. Switches OK when 120 is from utility, PLC resets when 120 is
from generator. Switch over to 120 supply is OK with either utility or
generator source.

Did disconnect one battery at a time, no change. Did add house
electrical load, as opposed to just exercising generator with no
transfer, no change.

??
Replace relay - with what?
Add capacitor to bridge during changeover - how big, where?
While only with generator source?

~)

Carl Denk wrote:
{Quote hidden}

2007\04\10@105130 by John Chung

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Carl can you provide a schematic to your setup?

John


--- Carl Denk <spam_OUTcdenkTakeThisOuTspamalltel.net> wrote:

{Quote hidden}

> --

2007\04\10@112020 by Howard Winter

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Carl,

On Tue, 10 Apr 2007 10:03:45 -0400, Carl Denk wrote:

> Just to summarize symptom: Relay drops out, switching PLC from 120VAC >
> 12 VDC switching supply to 2 lead acid batteries connected with diodes
> to relay. Switches OK when 120 is from utility, PLC resets when 120 is
> from generator. Switch over to 120 supply is OK with either utility or
> generator source.

It could be that there is a voltage-step when you change from generated to battery supply - there will be at least a
dip as the contacts change over (I assume they're not a make-before-break contacts).

> Did disconnect one battery at a time, no change. Did add house
> electrical load, as opposed to just exercising generator with no
> transfer, no change.
>
> ??
> Replace relay - with what?

Something solid-state that will switch without a gap?  Perhaps just a set of diodes, making sure that the
mains/generated voltage is above that of the batteries, so the latter are only used when needed?

> Add capacitor to bridge during changeover - how big, where?

This can't hurt, and may solve the problem.  Start with a couple of hundred uF immediately after the relay, and see if
it helps.  But make sure it has a high enough voltage rating - it may see some spikes that would damage it.  I'd go for
50V rating at least.

> While only with generator source?

Different voltages?  Although they are all nominally 12V, the actual voltages - especially under load - will be different.  
You are introducing a sudden change of voltage, which may be enough to trigger the PLC to reset.  I have two
"proper" UPSs (made by APC) in series, which they don't recommend, and when the upstream one switches from mains
supply to battery supply, the downstream one *sometimes* switches itself to battery supply, reporting something like:
"High rate of change of mains voltage" - it reverts a few seconds later.

Good luck!

Cheers,


Howard Winter
St.Albans, England


2007\04\10@115225 by Dwayne Reid

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Please try this:

Power PLC directly from one of the batteries.  Repeat tests.

If PLC does NOT reset, you know the problem and the cure.

If PLC DOES reset, well, I guess I'll go fishing for other ideas.

Let us know what happens.

dwayne

PS - I still think the momentary interruption in PLC power when the
relay switches is the cause of your problems.  The above test should
confirm whether I'm right or not.

dwayne

At 08:03 AM 4/10/2007, Carl Denk wrote:
{Quote hidden}

--
Dwayne Reid   <.....dwaynerKILLspamspam@spam@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 22 years of Engineering Innovation (1984 - 2006)
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2007\04\10@133527 by Peter P.

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Carl Denk <cdenk <at> alltel.net> writes:

> Just to summarize symptom: Relay drops out, switching PLC from 120VAC >
> 12 VDC switching supply to 2 lead acid batteries connected with diodes
> to relay. Switches OK when 120 is from utility, PLC resets when 120 is
> from generator. Switch over to 120 supply is OK with either utility or
> generator source.
>
> Did disconnect one battery at a time, no change. Did add house
> electrical load, as opposed to just exercising generator with no
> transfer, no change.
>
> ??
> Replace relay - with what?
> Add capacitor to bridge during changeover - how big, where?
> While only with generator source?

Try to add serious filtering after the relay before the PLC. Corcom etc line
filter grounded at the PLC and with real earth. I suspect there is conducted
noise and/or a ground loop that is opened when the relay opens on the generator
side. Analyze your grounds and see what the relay does (not) separate.

hope this helps,
Peter P.


2007\04\10@150641 by Carl Denk

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List doesn't like attachment and I don't have access to a web site, ask
me for schematic at: cdenkspamKILLspamalltel.net.

I will check grounds, but think there is only one. However, the
generator is attached to underground conduit at it's end, and to the
panel area by several metallic conduits, and house has several good
ground rods, including, at the meter and to the main panel. The battery
at the generator is grounded to the generator and has a 12 ga. copper
wire to the PLC and inside battery grounds. I was pretty careful with
isolating the hot sides with either double throw switch, relays, or opto
isolators.

Powered from the non-generator engine battery, all OK. If it's powered
from the engine's battery, upon starter energizing, voltage is pulled
down to 9 volts, and PLC resets, had that issue some time ago, and added
a second battery (from a homebuilt airplane we had dismantled) with the
diodes to select the higher voltage one as described earlier. No
problems when powered off either battery, except when starting. Issue
only when switching from the switching power supply to battery, when the
relay coil is deenrgized and spring pulls contacts open. No problem when
coil is energized and contacts are switching.

Added 2000 MFD, 50VDC capacitor (+ to switching power supply, - to PLC
supply side) at relay terminals, problem went away. Tried 1000 mfd, 25
volt, problem returned. Guess that's one fix, probably order a selection
of caps and trial and error how small I can get. A second round of
testing of all modes was OK with the 2000 mfd.

Also, in place of the IAC-15 input module, have used a H11AA2 AC input
optoisolator. On the AC side, a 22k resistor in series to the 120 volt.
On the output side, a 10K resistor pullup, and .33 MFD cap to 12 volt on
the output to th PLC in port, and other side to ground. It seems to work
equally well as the module at detecting the AC power presence..

Dwayne Reid wrote:
{Quote hidden}

2007\04\10@191610 by Dwayne Reid

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I think that I'm still gonna beat the same drum.

Eliminate the relay that switches the PLC power line.  Use a diode
array of 3 diodes so that whichever voltage is highest feeds the PLC
power input.

Ensure that the AC power supply is higher than the float voltage
present on the batteries when fully charged.  No relay needed.

Then try it and see how you make out.

dwayne

PS: the only problem with adding that large capacitor after the relay
contacts is inrush current eventually damaging the relay
contacts.  But I still don't see the need for the relay and think
that eliminating it will get rid of your problem.

dwayne

At 01:06 PM 4/10/2007, Carl Denk wrote:

{Quote hidden}

--
Dwayne Reid   <.....dwaynerKILLspamspam.....planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 22 years of Engineering Innovation (1984 - 2006)
 .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-
    `-'   `-'   `-'   `-'   `-'   `-'   `-'   `-'   `-'
Do NOT send unsolicited commercial email to this email address.
This message neither grants consent to receive unsolicited
commercial email nor is intended to solicit commercial email.

2007\04\10@194310 by Carl Denk

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I wish I could do  that, but The battery voltages are fixed at what they
are, and the maximum voltages of the other parts is fixed too. Looks
like the next higher voltage supply is 15 volts, that's a little higher
than I would like to operate, plus the batteries float at 13.8 volts.
That relay is quite beefy, with 10 amp contacts, and if the move maybe a
dozen times a year, that would be a lot, plus it could be put on
maintenance schedule to replace every few years. The whole system is
based on the Kohler engine electrical which is 12 volts (nominal), then
all the sensors (pressure, voltages, temperatures) are selected and
calibrated based on the 12 volts.

What about adding a diode across the contacts with the capacitor ?

Dwayne Reid wrote:
{Quote hidden}

2007\04\11@084526 by Carl Denk

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If someone could come up with a replacement for the relay, that would be
great. Need to actually switch between the 2 batteries OR'ed together
and the 12 VDC power supply. Thinking FET's or something, but, although
LOGIC, TTL, some OP-AMP design and Ohm's law is my level, my expertice
is more toward structural concrete. ~)

Carl Denk wrote:
{Quote hidden}

2007\04\11@110755 by Dwayne Reid

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Hi there, Carl.

I know that all the 12V stuff is fixed.  But doesn't the PLC operate
up to 24Vdc input?  Remember, the only thing the output from the 3
diodes feeds is the PLC supply rail.

Also keep in mind that the supply that feeds the PLC doesn't have to
be regulated.  It simply needs to be higher than the float voltage on
the batteries - that ensures that the charge is not being removed
from the batteries while AC power is available.

I guess that I may not be seeing the whole picture.

dwayne

At 05:43 PM 4/10/2007, Carl Denk wrote:
{Quote hidden}

--
Dwayne Reid   <EraseMEdwaynerspam_OUTspamTakeThisOuTplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 22 years of Engineering Innovation (1984 - 2006)
 .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-
    `-'   `-'   `-'   `-'   `-'   `-'   `-'   `-'   `-'
Do NOT send unsolicited commercial email to this email address.
This message neither grants consent to receive unsolicited
commercial email nor is intended to solicit commercial email.

2007\04\11@114258 by Carl Denk

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The PLC also closes the ground side to the 12 volt relay coils which are
fed from the PLC 12 volt supply, and has 8 ADC converters.  And yes the
PLC can operate easily up up to  24 volts.  Here's a link to the PLC  
http://www.tri-plc.com/t100md888.htm. The outputs on the PLC are
ULN2803A and TPIC6A595NE.    The PLC does have a 5 VDC Vref for the ADC
that I use most of the time, would have to look and see if somewhere I
use the 12 volt.

Would be nice to have an electronic switch that works off the output of
the AC optoisolator, defaults to the AC, except when AC is down, but
that's beyond me. Wouldn't bother me to use one or 2 of those OPTO 22
type I/O modules. Have used the IAC-15.

Dwayne Reid wrote:
{Quote hidden}

2007\04\11@142005 by John Chung

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Carl,

  I have read your circuit diagram. I have some
questions. Have you calculated the time constant for
the relay? The amount of charge and discharge for the
resistance and the inductance of the relay? From what
I see the relay switches the power between them which
is fine but the problem is that when does it actually
switch over?

Regards,
John




--- Carl Denk <cdenkspamspam_OUTalltel.net> wrote:

{Quote hidden}

> --

2007\04\11@143512 by John Chung

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There was a diagram I saw on the power switching.
Try to lookup for AVR butterfly. The power circuit has
such roll over.

www.atmel.com/dyn/products/tools_card.asp?tool_id=3146
Look for User guide.
Schematic 4 of 4.




John


--- Carl Denk <@spam@cdenkKILLspamspamalltel.net> wrote:

{Quote hidden}

> --

2007\04\11@171654 by Carl Denk

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I'm not an electrical engineer  :( , the formal training in that area
was 1 semester in 1963, and haven't calculated any of that. There was
question in my mind if the relay would actually switch over quick
enough, that the latency of the power supply and PLC would cover the
time. Since I had the necessary hardware laying around, I tried it, and
it worked on the bread board. Went through 2 versions of the PCB where
other things changed (AC voltage and frequency measurement to the PLC is
on the same board). It was just recently I stumbled on the issue, after
a year of operation, it has switched over OK many times with utility
power, and then with generator power it fails in the direction of the
spring moving the contacts every time. In the direction that the coil
moves the contacts, it's OK either power source.

By asking when does it actually switch over, I assume you are talking
the brief time from when the 120 volt is down to the contacts moving.
All I can say is the 120 volt wire to both  the relay coil and the 12
VDC power supply are the same length from the plug strip within say 6".
The power supply is a International Power model IHC12-34 with over
voltage protection.

I looked at the AVR butterfly info. With the 2 sources and diodes is
what I have for the 2 batteries. I don't know the function of R400,
maybe to charge maintain the battery. Unfortunately the 12 volt that is
my  preferred source is less voltage than the batteries, and the diodes
won't work. The capacitor across the contact points seems to be working,
but it has been pointed out, this could be hard on the contacts, but the
usage is going to be very few cycles, could be less than 6 in a year.

Thanks again. :)



John Chung wrote:
{Quote hidden}

>> --

2007\04\11@181543 by Richard Prosser

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Just a quick comment that may be relevent.
The relay will NOT take the same amount of time to connect and disconnect.
In order to connect the current in the coil has to increase to a level
sufficient to generate enough magnetic flux to start the armature
moving. To disconnect, the
coil current has to decay to a low level. Normally, the hold current
is a lot less that the pull-in current so there is considerable
hysteresis involved. If a flywheel diode is used the current can take
a noticable time to decay before the actual disconnection occurs. This
can be sped up using zener diodes (or MOVs etc.) in place of the
flywheel diode if required but the switching device must be OK with
the higher voltage generated.


RP

On 12/04/07, Carl Denk <RemoveMEcdenkTakeThisOuTspamalltel.net> wrote:
{Quote hidden}

2007\04\11@191259 by Carl Denk

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Not familiar with term "flywheel diode", tell me more. :)  Since the
issue seems to be with decaying voltage wanting to be quicker, then the
zener diodes or MOV's might help. Since this is AC current, I'm assuming
MOV's might help, and am I correct in assuming that adding a MOV  at the
coil might be a fix. Tried a V150LA10A MOV across the coil terminals
without the capacitor, no good. Don't kow how to use zeners with AC
current.

Richard Prosser wrote:
{Quote hidden}

2007\04\11@201833 by Richard Prosser

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Sorry, I was assumiing that the coil current was DC. However, a sudden
disconnection of the coil would still be likely to introduce a voltage
spike so some sort of supression would be advised.
If this is the problem then I would have though the MOV you tried
would have showed some inprovement.

If using zeners, connect them back to back and use a voltage rating
2-3 times the applied rms.
However, whatever is doing the relay switching needs to be able to
withstand whatever voltage is likely to be generated.

The term "flywheel" diode comes from it's operation. With coil current
established, if the coil is disconnected the current in the coil
(inductor) will not change quickly and the voltage at the terminals
will increase to attempt to maintain the coil current. The "Flywheel
diode" is placed to permit the current to pass through the coil and
decay gradually due to the coil resistance. The current then rotates
though the diode and coil, in a similar manner to a flywheel winding
down. That's about as well as I can describe it anyway.
By replacing the standard diode with a zener or MOV the voltage builds
across the zener etc., the current is the same (due to the inductance)
and so the power level goes up. Since there is only a limited amount
of energy  in the system,  it dissipates more quickly.


RP

On 12/04/07, Carl Denk <cdenkEraseMEspam.....alltel.net> wrote:
{Quote hidden}

2007\04\11@205011 by Carl Denk

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That OK, the tread is getting a little long. The idea was (is) AC power
drops,  relay switches hopefully before the PLC drops out. Any thoughts
about adding MOV's in parallel across the coil, or a smaller relay with
less mass to the moveable contact and less induction allowing the
contact to move more quickly. The current relay is 10 amp contacts,  I
only need 3 amps. (and I'm brainstorming) or a rectifier bridge, DC
coil, and voltage dropping resistor.

:)

Richard Prosser wrote:
{Quote hidden}

2007\04\11@230131 by John Chung

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--- Carl Denk <RemoveMEcdenkEraseMEspamEraseMEalltel.net> wrote:

I am not an engineer in training but I continuously
drive myself to learn more electronics. :)

{Quote hidden}

 As time pass by the age of the components start to
show like increased resistance and etc.

{Quote hidden}

 www.allaboutcircuits.com/vol_1/chpt_16/3.html
Read this instead for the calculation. The difference
of the wire resistance is minimal at best. I believe
there is some where at the site above to calculate the
wire resistance. There are other resistance to
calculate.... The input of the PLC is one for example.




John


     
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2007\04\12@091412 by Carl Denk

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Thanks for the link on calculation. I noted that it used SPICE which I
have used also for OP-AMP design in particular. While searching for
impedance and other data on the relay, I found some interesting info:
http://ecatalog.squared.com:8080/TechLibWeb/download/?url=http%3A%2F%2Fecatalog%2Esquared%2Ecom%2Fpubs%2FMachine%20Control%2FRelays%20and%20Timers%2FRelays%2C%20General%20Purpose%2FRelays%2C%20Power%2F8501CT0301%2Epdf

Typical pick up time     AC coil: approximately 12 ms
                                       DC coil: approximately 18 ms

Typical Drop Out time   AC coil: approximately 12 ms
                                        DC coil: approximately 7 ms

It seems that by going to a DC coil, I might move the problem to
switching in the other direction. There was no other info on the coils.
Interesting that they claim pick up and drop out times to be the same
with AC. I only have DMM's and a logic probe for test equipment, wish I
had a scope, but it's not in family budget at this time. Without the
inductance of the coil, or a scope to measure times and things, think
that's a dead end. Don't know where the times above would set on the
curves calculated if knew impedance. Don't mind spending a few $$ on
parts to try out. Don't have negative attitude with respect to learning,
i.e. now know how to implement PIC project, programming in "C" , ladder
logic, "BASIC" that skills were slim 3 years ago, but my time, even
though retired has priorities too. :( Usually pointed in a direction, I
can take it from there. :)

Thanks again for the input, it's appreciated!


John Chung wrote:
{Quote hidden}

2007\04\12@111420 by John Chung

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Carl,

 I know of the pains when we are with no scope. I
suggest this instead. You have some PIC skills :) Use
it to determine the charge and discharge time. It
would provide the data you need after programming it.


--- Carl Denk <RemoveMEcdenkTakeThisOuTspamspamalltel.net> wrote:

> Thanks for the link on calculation. I noted that it
> used SPICE which I
> have used also for OP-AMP design in particular.
> While searching for
> impedance and other data on the relay, I found some
> interesting info:
>
ecatalog.squared.com:8080/TechLibWeb/download/?url=http%3A%2F%2Fecatalog%2Esquared%2Ecom%2Fpubs%2FMachine%20Control%2FRelays%20and%20Timers%2FRelays%2C%20General%20Purpose%2FRelays%2C%20Power%2F8501CT0301%2Epdf
{Quote hidden}

 I don know how they come out with that
calculation...
So I won't be able to provide reference on the AC
calculation...... Have to read more...

{Quote hidden}

 Learning is VERY rewarding when you fix stuff :)

 John


     
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