Fuse for an AC motor

[Uriah]

I have these 110VAC single phase small AC motors which are driving a
bunch of gears and other parts. Every now and then they will jam up
for one reason or another. They will sit there and fry and I will
have to change the motor out. So my question is can I put a in-line
fuse on one of the leads going to the AC source? Will a motor that
gets stopped show in increase in current enough to blow a fuse of the
right size? I called the company that sold them to me and they said
their motors are thermally protected but once they jam and I go up to
them and the power is still on they are to hot to touch. Then if I
let them cool down they are dead and won't start back up. Just to be
clear: Will a fuse protect a motor if the shaft is forcibly stopped
with the power on?

Thanks
Uriah

 

[Homer J Simpson]

I have these 110VAC single phase small AC motors which are driving a
bunch of gears and other parts. Every now and then they will jam up
for one reason or another. They will sit there and fry and I will
have to change the motor out. So my question is can I put a in-line
fuse on one of the leads going to the AC source? Will a motor that
gets stopped show in increase in current enough to blow a fuse of the
right size? I called the company that sold them to me and they said
their motors are thermally protected but once they jam and I go up to
them and the power is still on they are to hot to touch. Then if I
let them cool down they are dead and won't start back up. Just to be
clear: Will a fuse protect a motor if the shaft is forcibly stopped
with the power on?

You can add a fuse but I doubt it will help much. What sort of amps/HP are
they?


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[Yukio YANO]

I have these 110VAC single phase small AC motors which are driving a
bunch of gears and other parts. Every now and then they will jam up
for one reason or another. They will sit there and fry and I will
have to change the motor out. So my question is can I put a in-line
fuse on one of the leads going to the AC source? Will a motor that
gets stopped show in increase in current enough to blow a fuse of the
right size? I called the company that sold them to me and they said
their motors are thermally protected but once they jam and I go up to
them and the power is still on they are to hot to touch. Then if I
let them cool down they are dead and won't start back up. Just to be
clear: Will a fuse protect a motor if the shaft is forcibly stopped
with the power on?

Thanks
Uriah

"motors are thermally protected "
Sounds like they already have a Thermal-Fuse wired in.
Replace same to restore !

Yukio YANO

 

[xrayjuan]

Put a motion sensor in the shaft that activate a relay to remove the AC in.
If you need a diagram, reply.

 

[Ross Herbert]

I have these 110VAC single phase small AC motors which are driving a
bunch of gears and other parts. Every now and then they will jam up
for one reason or another. They will sit there and fry and I will
have to change the motor out. So my question is can I put a in-line
fuse on one of the leads going to the AC source? Will a motor that
gets stopped show in increase in current enough to blow a fuse of the
right size? I called the company that sold them to me and they said
their motors are thermally protected but once they jam and I go up to
them and the power is still on they are to hot to touch. Then if I
let them cool down they are dead and won't start back up. Just to be
clear: Will a fuse protect a motor if the shaft is forcibly stopped
with the power on?

Thanks
Uriah

Don't muck around trying to protect your motors with fuses. Long
experience has shown the only reliable method is to use a motor
protection circuit breaker such as Rockwell Autonmation 140M series.
http://www.ab.com/en/epub/catalogs/12768/229240/229254/229469/3100798/3100802/

Of course, you don't get anything for nothing - one of these could
cost nearly as much (or more) than a new motor (depending upon motor).

 

[Puckdropper]

Don't muck around trying to protect your motors with fuses. Long
experience has shown the only reliable method is to use a motor
protection circuit breaker such as Rockwell Autonmation 140M series.
http://www.ab.com/en/epub/catalogs/12768/229240/229254/229469/3100798/3
100802/

Of course, you don't get anything for nothing - one of these could
cost nearly as much (or more) than a new motor (depending upon motor).

Just out of curiousity, are they reusable? Blow it a couple/three times
and you might start saving money.

Puckdropper

 

[jasen]

I have these 110VAC single phase small AC motors which are driving a
bunch of gears and other parts. Every now and then they will jam up
for one reason or another. They will sit there and fry and I will
have to change the motor out. So my question is can I put a in-line
fuse on one of the leads going to the AC source? Will a motor that
gets stopped show in increase in current enough to blow a fuse of the
right size?

they will show an increase, but it's hard to get the right size in a fuse.

I called the company that sold them to me and they said
their motors are thermally protected but once they jam and I go up to
them and the power is still on they are to hot to touch. Then if I
let them cool down they are dead and won't start back up. Just to be
clear: Will a fuse protect a motor if the shaft is forcibly stopped
with the power on?

there devices designed to protect motors.

Bye.
Jasen

 

[Phil Allison]

"Uriah"

I have these 110VAC single phase small AC motors which are driving a
bunch of gears and other parts. Every now and then they will jam up
for one reason or another. They will sit there and fry and I will
have to change the motor out.

** You need a self resetting over-temp cut-out.

Just attach or glue one to the hottest part of the motor and wire it in
series with the AC power.

Piece of cake.

Eg:

http://au.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=732590




........ Phil

 

[Uriah]

Ok, so the bottom line is no a fuse won't work? But it looks like I
have a number of good ideas. Thank you to all. I will start checking
into all of them. They all sound very workable.

Thanks
Uriah

 

[Chris]

I have these 110VAC single phase small AC motors which are driving a
bunch of gears and other parts. Every now and then they will jam up
for one reason or another. They will sit there and fry and I will
have to change the motor out. So my question is can I put a in-line
fuse on one of the leads going to the AC source? Will a motor that
gets stopped show in increase in current enough to blow a fuse of the
right size? I called the company that sold them to me and they said
their motors are thermally protected but once they jam and I go up to
them and the power is still on they are to hot to touch. Then if I
let them cool down they are dead and won't start back up. Just to be
clear: Will a fuse protect a motor if the shaft is forcibly stopped
with the power on?

Thanks
Uriah

Good morning, Uriah. Your motors are probably "thermally protected",
as mentioned above. While you may be able to take apart he motor and
replace the thermal cutoff, this is what a fuse or circuit breaker is
for.

What you may want to do is put an AC ammeter in series with the AC
line going to the motor and measure the normal load current. Install
a line voltage slow blow fuse rated for about 150% of that current in
series with the motor. The fuse will blow before the motor cutoff.
Test it by stalling the motor and making sure the fuse blows before
the motor cooks.

Unfortunately, most ccircuit breakers are pretty slow, and might not
cut off for the small AC gearmotors before damage is done.

Fuses are much cheaper than motors. You can get Littelfuse 3AG 1A
slow blow fuses for $0.70 ea. in 10 qty. at Mouser.

http://www.mouser.com/catalog/629/477.pdf

Good luck
Chris

 

[Jamie]

Ok, so the bottom line is no a fuse won't work? But it looks like I
have a number of good ideas. Thank you to all. I will start checking
into all of them. They all sound very workable.

Thanks
Uriah

do it right, use a fuse rated at 150% of max load, use a
reset able overload rated 100% of the motor,that will open up the
circuit that drives the motor.
you should be using a Motor Starter with overloads in it.

 

[Michael A. Terrell]

do it right, use a fuse rated at 150% of max load, use a
reset able overload rated 100% of the motor,that will open up the
circuit that drives the motor.
you should be using a Motor Starter with overloads in it.


"I'm never wrong, once i thought i was, but was mistaken"

Once again, you are wrong. Busman and Littlefuse make fuses for
motor applications. You can't just toss out a random percentage for all
applications. More demanding applications benefit from soft start
controllers, as well.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[jasen]

What you may want to do is put an AC ammeter in series with the AC
line going to the motor and measure the normal load current. Install
a line voltage slow blow fuse rated for about 150% of that current in
series with the motor. The fuse will blow before the motor cutoff.
Test it by stalling the motor and making sure the fuse blows before
the motor cooks.

Unfortunately, most ccircuit breakers are pretty slow, and might not
cut off for the small AC gearmotors before damage is done.

depends on the breaker, some are faster than ordinary fuses.

Fuses are much cheaper than motors. You can get Littelfuse 3AG 1A
slow blow fuses for $0.70 ea. in 10 qty. at Mouser.

problem is overload is about 140% of the run current and even a
fuse rated for the exact run current can take minutes to respond
to that,

Bye.
Jasen

 

[Homer J Simpson]

Ok, so the bottom line is no a fuse won't work? But it looks like I
have a number of good ideas. Thank you to all. I will start checking
into all of them. They all sound very workable.

You CAN protect them but a regular fuse is unlikely to help. What sort of
HP/amps are they?

 

[Jamie]

Once again, you are wrong. Busman and Littlefuse make fuses for
motor applications. You can't just toss out a random percentage for all
applications. More demanding applications benefit from soft start
controllers, as well.

Those aren't random numbers pecker head.
I work in the business about every day of the
week.
Go find some other to make your self look good, you're barking up the
wrong tree.
And for your information, get get visits from Busman annually showing
us their product line.

 

[Ross Herbert]

Just out of curiousity, are they reusable? Blow it a couple/three times
and you might start saving money.

Puckdropper

Of course the motor protection CB's are reusable. That is why they are
called CIRCUIT BREAKERS. Once reset, they are ready for action again.
Their main advantage is that if a marginal overload in the motor
occurs due to a shorted turn or some such fault, the CB will detect it
before it overheats and a fire occurs.

 

[Ross Herbert]

The link to the Rockwell Automation CB's shows they are available down
to 100mA so small motors are catered for. The whole idea of producing
a specific motor protection CB is that it will be just slow enough in
operation to prevent unneccessary tripping due to short term
overloads. Fuses are totally unsuitable for motor protection for a
couple of reasons;

If too low a current rating they trip frequently on short term
overloads - very annoying.

If too high a current rating they will not detect marginal long term
overloads which can result in gradual heat buildup and possibility of
fire.

Motor protection CB's are the only reliable method of an easily
installed method of protection. While Phil's suggestion of a thermal
switch mounted on the motor is valid it is more difficult to install.

 

[Michael A. Terrell]

Those aren't random numbers pecker head.

How old are you? You sound like you're about eight years old.

I work in the business about every day of the
week.

Sure you do. The requirements vary,dependiong on how a motor is
used. Some staret wth little, or no load, while others start with a
heavy laod. The starting current is much higher in the second case.

Go find some other to make your self look good, you're barking up the
wrong tree.

Take yor own advice, Skippy.

And for your information, get get visits from Busman annually showing
us their product line.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Jamie]

How old are you? You sound like you're about eight years old.

Look, don't get me started, You wouldn't like the recoil.
and if it makes you any happier, i'll be 48 the end of this
month and have been in the business professionally since 19.

 

[Michael A. Terrell]

Look, don't get me started, You wouldn't like the recoil.
and if it makes you any happier, i'll be 48 the end of this
month and have been in the business professionally since 19.

Recoil?
BWHAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA!!!


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida