Inverter glitch question

[Nick Hull]

I'm using a cheap 300 watt inverter with 2 golf cart batteries to power
emergency lights during power failures. I found that 12 vdc
flourescents were expensive and had short lives, so I'm using 110vac CFs
powered by the 300 watt inverter. Works very well EXCEPT for an
occasional glitch, where the inverter turns off due to a transient hab
has to be manually reset.

I'm not sure where the transient comes from, I can not duplicate it in
tests. The inverter is connected to the batterys and a float charger
keeps them topped. Plugging & unplugging the float charger does
nothing. The Inverter output goes around the house to various CF bulbs
on manual switches and one automatic switch, maybe 50' total wiring some
of which parallels existing house power wiring but no motors or heavy
loads.

Not much info, wut what could be causing the glitch that turns my
inverter off and how might I fix it or troubleshoot the problem?

 

[Bob Urz]

I'm using a cheap 300 watt inverter with 2 golf cart batteries to power
emergency lights during power failures. I found that 12 vdc
flourescents were expensive and had short lives, so I'm using 110vac CFs
powered by the 300 watt inverter. Works very well EXCEPT for an
occasional glitch, where the inverter turns off due to a transient hab
has to be manually reset.

I'm not sure where the transient comes from, I can not duplicate it in
tests. The inverter is connected to the batterys and a float charger
keeps them topped. Plugging & unplugging the float charger does
nothing. The Inverter output goes around the house to various CF bulbs
on manual switches and one automatic switch, maybe 50' total wiring some
of which parallels existing house power wiring but no motors or heavy
loads.

Not much info, wut what could be causing the glitch that turns my
inverter off and how might I fix it or troubleshoot the problem?

Maybe your ballast don't like the SQUARE WAVE output your cheap inverter
is putting out? How hot are your ballast's? How many watts of load?
Continuous rating of your inverter? How hot is the inverter?
Maybe a higher rated sine wave inverter would solve your problems.

Bob

 

[Nick Hull]

Maybe your ballast don't like the SQUARE WAVE output your cheap inverter
is putting out? How hot are your ballast's? How many watts of load?
Continuous rating of your inverter? How hot is the inverter?
Maybe a higher rated sine wave inverter would solve your problems.

The lights work well with the Sq (modified sine) wave output, ballasts
run cool and the inverter runs cool. The problem SEEMS to occur when
the power goes out and comes back on so there are surges on the mains.

 

[CJT]

Nick Hull wrote:



Maybe your ballast don't like the SQUARE WAVE output your cheap inverter
is putting out? How hot are your ballast's? How many watts of load?
Continuous rating of your inverter? How hot is the inverter?
Maybe a higher rated sine wave inverter would solve your problems.

The lights work well with the Sq (modified sine) wave output, ballasts
run cool and the inverter runs cool. The problem SEEMS to occur when
the power goes out and comes back on so there are surges on the mains.
[/QUOTE]
I'd look closely at your automatic switch. Perhaps it's generating
an RF pulse when it switches state that is somehow reaching your
inverter. The solution might be as simple as a capacitor across the
switch, or a cheap filter between it and the inverter.

 

[JURB6006]

Let me get this straight, this UPS is only hooked to one of the branch
circuits, not the mains.

If I'm correct, there are only flourescent lights as a load here. Is this
correct ?

If so I have an opinion that might help. Before these lights fire up, they
present almost no load. With no load the proximity to the other wires and other
factors may be impressing a "hum" on the output line. If the logic control in
the UPS detects this it may either see it as a fault, or who knows.

Flying by the seat of my pants here, I'd connect at least one incandescent
light to the output and see if it corrects the problem. I think it's worth a
try at least.

JURB

 

[Nick Hull]

Let me get this straight, this UPS is only hooked to one of the branch
circuits, not the mains.

If I'm correct, there are only flourescent lights as a load here. Is this
correct ?

If so I have an opinion that might help. Before these lights fire up, they
present almost no load. With no load the proximity to the other wires and
other
factors may be impressing a "hum" on the output line. If the logic control in
the UPS detects this it may either see it as a fault, or who knows.

Flying by the seat of my pants here, I'd connect at least one incandescent
light to the output and see if it corrects the problem. I think it's worth a
try at least.

Interesting reasoning. The only loads are compact flourescents, and all
are off. One of them will switch on about 5-10 seconds after a power
failure. There is one neon light on 100% of the time, about 1/4 watt.

I don't want to have an incandescent light on all the time, unless it is
very small. Are there any 110 volt incandescents less than 4 watts? Or
maybe I could put 2 4 watters in series?

 

[Nick Hull]

Nick Hull wrote:


I'm using a cheap 300 watt inverter with 2 golf cart batteries to power
emergency lights during power failures. I found that 12 vdc
flourescents were expensive and had short lives, so I'm using 110vac CFs
powered by the 300 watt inverter. Works very well EXCEPT for an
occasional glitch, where the inverter turns off due to a transient hab
has to be manually reset.

I'm not sure where the transient comes from, I can not duplicate it in
tests. The inverter is connected to the batterys and a float charger
keeps them topped. Plugging & unplugging the float charger does
nothing. The Inverter output goes around the house to various CF bulbs
on manual switches and one automatic switch, maybe 50' total wiring some
of which parallels existing house power wiring but no motors or heavy
loads.

Not much info, wut what could be causing the glitch that turns my
inverter off and how might I fix it or troubleshoot the problem?


Maybe your ballast don't like the SQUARE WAVE output your cheap inverter
is putting out? How hot are your ballast's? How many watts of load?
Continuous rating of your inverter? How hot is the inverter?
Maybe a higher rated sine wave inverter would solve your problems.

The lights work well with the Sq (modified sine) wave output, ballasts
run cool and the inverter runs cool. The problem SEEMS to occur when
the power goes out and comes back on so there are surges on the mains.
[/QUOTE]
I'd look closely at your automatic switch. Perhaps it's generating
an RF pulse when it switches state that is somehow reaching your
inverter. The solution might be as simple as a capacitor across the
switch, or a cheap filter between it and the inverter.[/QUOTE]

My 'automatic switch' is just a DC relay powered from the AC mains with
rectification and a capacitor. If the power fails the cap will hold the
relay in for 10 seconds, then it drops out to energize the CF light. I
don't see any RF pulse there, do you?

 

[Art Todesco]

Compact fluorescents use an electronic ballast. Depending on the lamp,
there may be some large inrush currents when they are 1st switched on.
Maybe you are just on the boarder line. Just a guess. You might try
turning on only 1/2 the lights. If it works, you could use 2 relays
with different time delays so they don't come on at the same time.

BTW, I know you mentioned 12 volt CFs. There are some CF spring-shaped
lamps available like the ones at
http://www.realgoods.com/shop/shop3.cfm?dv=3&dp=301&ts=3033509&kw=spring lamp.

Anyway, just another thought.

 

[CJT]

My 'automatic switch' is just a DC relay powered from the AC mains with
rectification and a capacitor. If the power fails the cap will hold the
relay in for 10 seconds, then it drops out to energize the CF light. I
don't see any RF pulse there, do you?

Only if there's arcing.

 

[Lionel]

My 'automatic switch' is just a DC relay powered from the AC mains with
rectification and a capacitor. If the power fails the cap will hold the
relay in for 10 seconds, then it drops out to energize the CF light. I
don't see any RF pulse there, do you?

Unless you quench it somehow, you'll get a big voltage spike, (resulting
in an RF glitch), any time a coil (such as your relay) is switched off.
Does the coil of the relay have a diode or cap across it to sink the
spike? If not, that may well be the cause of your problem.

When switching heavy loads with a relay, it's also good practice to put
an RC supression circuit across the contacts to prevent sparking, which
will generate RF, as well as being bad for the contacts.

 

[Nick Hull]

Unless you quench it somehow, you'll get a big voltage spike, (resulting
in an RF glitch), any time a coil (such as your relay) is switched off.
Does the coil of the relay have a diode or cap across it to sink the
spike? If not, that may well be the cause of your problem.

The coil isn't 'switched' off, it just slowly decays until it drops out
for lack of current, while current is still flowing but too weak to hold
the relay in.

When switching heavy loads with a relay, it's also good practice to put
an RC supression circuit across the contacts to prevent sparking, which
will generate RF, as well as being bad for the contacts.

Very true, but this is only switching a 7 watt CF bulb.

 

[Nick Hull]

Compact fluorescents use an electronic ballast. Depending on the lamp,
there may be some large inrush currents when they are 1st switched on.
Maybe you are just on the boarder line. Just a guess. You might try
turning on only 1/2 the lights. If it works, you could use 2 relays
with different time delays so they don't come on at the same time.

I'm only turning one light on automatically

BTW, I know you mentioned 12 volt CFs. There are some CF spring-shaped
lamps available like the ones at

<http://www.realgoods.com/shop/shop3.cfm?dv=3&dp=301&ts=3033509&kw=spring
%20lamp.>

Interesting url, I'll probably try that route also.

 

[Fred McKenzie]

<< The coil isn't 'switched' off, it just slowly decays until it drops out
for lack of current, while current is still flowing but too weak to hold
the relay in.

When switching heavy loads with a relay, it's also good practice to put
an RC supression circuit across the contacts to prevent sparking, which
will generate RF, as well as being bad for the contacts.

Very true, but this is only switching a 7 watt CF bulb. >>

Nick-

After reading all the symptoms and suggested causes, it appears that everything
is in order and should work. This leaves the possibliity of a malfunction.

One possibility is that the circuit to the switched CF bulb has an intermittent
short circuit or other high current condition. The inverter will most likely
shut down if shorted, rather than blowing a fuse.

Another possibility is that the inverter "just does that". Substituting a
borrowed inverter may clear up the problem, unless it happens so seldom that
you can't be sure if it is fixed!

One other thing I've observed, is that a particular (MFJ) switched DC power
supply shuts down when I connect the 300 Watt Radio Shack inverter. In your
case, I would expect the battery to act as a buffer, supplying any necessary
peak startup current. Even if it occasionally failed to start, the inverter
should still start (or continue to run) from the battery until the battery ran
down.

Fred