Electrical Engineering - UPS overload question

Author

UPS overload question

straightnut

2007-12-31, 9:25 am

My father is afraid of his treadmill suddenly stopping while he's
walking due to a power outage. I figured that a ups backup could give
him some time to step off before it stopped. But I figured that the
least expensive one with the lowest power rating would work, since I
assumed that the power rating was only to give you an estimate of how
long the unit will power an item.

Since most of the ups units offer several minutes for a low load, I
figured that it would give a more than adequate 10 to 20 seconds at
the higher load of a treadmill.

Will it work or will something trip inside the unit if the load is
greater than the rating?

Thanks,
Jeff

Palindrome

2007-12-31, 1:25 pm

straightnut wrote:
> My father is afraid of his treadmill suddenly stopping while he's
> walking due to a power outage. I figured that a ups backup could give
> him some time to step off before it stopped. But I figured that the
> least expensive one with the lowest power rating would work, since I
> assumed that the power rating was only to give you an estimate of how
> long the unit will power an item.
>
> Since most of the ups units offer several minutes for a low load, I
> figured that it would give a more than adequate 10 to 20 seconds at
> the higher load of a treadmill.
>
> Will it work or will something trip inside the unit if the load is
> greater than the rating?
>
Entirely wrong, I'm afraid. If the treadmill takes significantly more
power than the UPS is designed to supply, the UPS will simply not
function, at all. Not even for a second. It is designed to sense an
overload condition and trip out under such conditions..

Worse still - the motor in the treadmill will typically draw extra power
during starting, over and above its rated power in use. A UPS must be
rated with that starting power in mind as well as the running power.

--
Sue

2007-12-31, 1:25 pm

"straightnut" <ck747sf@aol.com> wrote in message
news:e5e4a7cd-ecaf-471f-ab31-7bcaeefb7309@i72g2000hsd.googlegroups.com...
> My father is afraid of his treadmill suddenly stopping while he's
> walking due to a power outage. I figured that a ups backup could give
> him some time to step off before it stopped.

How often does the power go out, and just how fast is he chugging along on
that thing?

If this is really something keeping folks up at night, simply fire up the
treadmill at the speed he uses it, unplug it, and see what happens. If the
treadmill is going fast, it should take a few seconds to come to a stop, and
if it's going real slow, you'll barely notice.

CS

straightnut

2007-12-31, 5:25 pm

On Dec 31, 10:30=A0am, Palindrome <m...@privacy.net> wrote:
> straightnut wrote:
>
>
>
> Entirely wrong, I'm afraid. If the treadmill takes significantly more
> power than the UPS is designed to supply, the UPS will simply not
> function, at all. Not even for a second. It is designed to sense an
> overload condition and trip out under such conditions..
>
> Worse still - the motor in the treadmill will typically draw extra power
> during starting, over and above its rated power in use. A UPS must be
> rated with that starting power in mind as well as the running power.
>
> --
> Sue

Thanks Sue. Exactly what I needed to know. The UPS is going back.
Jeff

straightnut

2007-12-31, 5:25 pm

On Dec 31, 11:33=A0am, "CS" <Idontw...@fcc.gov> wrote:
> "straightnut" <ck74...@aol.com> wrote in message
>
> news:e5e4a7cd-ecaf-471f-ab31-7bcaeefb7309@i72g2000hsd.googlegroups.com...
>
>
> How often does the power go out, and just how fast is he chugging along on=

> that thing?
>
> If this is really something keeping folks up at night, simply fire up the
> treadmill at the speed he uses it, unplug it, and see what happens. =A0If =
the
> treadmill is going fast, it should take a few seconds to come to a stop, a=
nd
> if it's going real slow, you'll barely notice.
>
> CS

He's in his late 70's and he loses his balance when the wind blows.
He's also very fearful. I think he had a fall once on it or he
slipped. Just thought it might be a good gift. Should have gotten him
socks.
Thanks for the help.
Jeff

phil-news-nospam@ipal.net

2008-01-01, 1:25 pm

On Mon, 31 Dec 2007 07:03:57 -0800 (PST) straightnut <ck747sf@aol.com> wrote:

| My father is afraid of his treadmill suddenly stopping while he's
| walking due to a power outage. I figured that a ups backup could give
| him some time to step off before it stopped. But I figured that the
| least expensive one with the lowest power rating would work, since I
| assumed that the power rating was only to give you an estimate of how
| long the unit will power an item.
|
| Since most of the ups units offer several minutes for a low load, I
| figured that it would give a more than adequate 10 to 20 seconds at
| the higher load of a treadmill.
|
| Will it work or will something trip inside the unit if the load is
| greater than the rating?

DC to AC power inversion tends to have very little overload headroom above
the nominal maximum operating range. Generators have more, but not a lot
more. Your utility mains electric supply has a lot more overload capacity.
They have some "big honk'n generators".

Even if the UPS does not trip when running on working mains supply, it may
well just quit when overloaded in DC operating mode when the mains goes out.

The only (IMHO) safe way to run a motor on a UPS is to get a UPS rated for
operation at the motor's LRA (lock rotor amps). And that would be a rather
large UPS.

FYI, I have found that running the circuitry of a house on a UPS, even a
large one rated for a whole circuit capacity, could well be unsafe because
it is unable to deliver the current (but at some rating levels would not
trip itself off, either) to magnetically trip building circuit breakers in
the event of a short circuit. Even a small generator can be unsafe for
just such a reason, or even a medium generator for a whole house (does it
have the ability to deliver the current needed to trip the main breaker
in the event of a fault that needs to trip the main?).

--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2008-01-01-1126@ipal.net |
|------------------------------------/-------------------------------------|

2008-01-02, 3:25 am

"straightnut" <ck747sf@aol.com> wrote in message
news:7f6791d1-39c9-4006-992d-5edfa73580e7@l6g2000prm.googlegroups.com...
On Dec 31, 11:33 am, "CS" <Idontw...@fcc.gov> wrote:
> "straightnut" <ck74...@aol.com> wrote in message
>
> news:e5e4a7cd-ecaf-471f-ab31-7bcaeefb7309@i72g2000hsd.googlegroups.com...
>
>
> How often does the power go out, and just how fast is he chugging along on
> that thing?
>
> If this is really something keeping folks up at night, simply fire up the
> treadmill at the speed he uses it, unplug it, and see what happens. If the
> treadmill is going fast, it should take a few seconds to come to a stop,
> and
> if it's going real slow, you'll barely notice.
>
> CS

He's in his late 70's and he loses his balance when the wind blows.
He's also very fearful. I think he had a fall once on it or he
slipped. Just thought it might be a good gift. Should have gotten him
socks.
Thanks for the help.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

He should use the hand rails. If it didn't come with them, either build
some or have somebody else do it...it shouldn't be too hard to rig something
up for him to hold on to. In my opinion, those will be safer than a UPS
anyway, with extra cords and boxes to trip over.

I've seen the shows where the guy on the treadmill goes flying backward or
forward due to a moment's inattention to foot placement, but unless your an
Olympic athelete running for your life, it's unlikely you'll go anywhere.

I do understand the fear of falling on these things. I was using mine to
speed my recovery from a quite nasty injury, and I'm not too coordinated in
the first place (hence the injury), so I made liberal use of the hand rails
and went real slow. To be honest, I got better results from working out in
the pool. If you fall there, you just get wetter.

CS

straightnut

2008-01-02, 9:25 pm

On Jan 2, 1:03=A0am, "CS" <Idontw...@fcc.gov> wrote:
> "straightnut" <ck74...@aol.com> wrote in message
>
> news:7f6791d1-39c9-4006-992d-5edfa73580e7@l6g2000prm.googlegroups.com...
> On Dec 31, 11:33 am, "CS" <Idontw...@fcc.gov> wrote:
>
>
>
>
>
>
[color=darkred]
>
>
on[color=darkred]
>
e[color=darkred]
he[color=darkred]
[color=darkred]
>
>
> He's in his late 70's and he loses his balance when the wind blows.
> He's also very fearful. I think he had a fall once on it or he
> slipped. Just thought it might be a good gift. Should have gotten him
> socks.
> Thanks for the help.
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> He should use the hand rails. =A0If it didn't come with them, either build=

> some or have somebody else do it...it shouldn't be too hard to rig somethi=
ng
> up for him to hold on to. =A0In my opinion, those will be safer than a UPS=

> anyway, with extra cords and boxes to trip over.
>
> I've seen the shows where the guy on the treadmill goes flying backward or=

> forward due to a moment's inattention to foot placement, but unless your a=
n
> Olympic athelete running for your life, it's unlikely you'll go anywhere.
>
> I do understand the fear of falling on these things. =A0I was using mine t=
o
> speed my recovery from a quite nasty injury, and I'm not too coordinated i=
n
> the first place (hence the injury), so I made liberal use of the hand rail=
s
> and went real slow. =A0To be honest, I got better results from working out=
in
> the pool. =A0If you fall there, you just get wetter.
>
> CS- Hide quoted text -
>
> - Show quoted text -

Okay thanks everyone.
Jeff

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