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induction motor vs "universal" motor - damaged by low voltage?

N

NG Neer

Jan 1, 1970
0
I recently had a good quality corded drill fail after less than 4
years (see link for pictures/details). I just read that running such
tools with very long or thin extension cords can make them fail, due
to the voltage drop in the extension cord causing the motor to draw
excessive current.

I've always known that running an induction motor on low voltage
causes execssive current and overheating, but I don't see how that
could be the case for "universal" motors with commutators. I mean,
isn't that how the trigger varies the speed of the drill, by reducing
the voltage to the motor? Reduced voltage due to losses in your cord
should just make the drill run slower, unless am I missing something
here??

link: http://mysite.verizon.net/rvotin/Dewalt_drill_failure.htm
 
I recently had a good quality corded drill fail after less than 4
years (see link for pictures/details). I just read that running such
tools with very long or thin extension cords can make them fail, due
to the voltage drop in the extension cord causing the motor to draw
excessive current.


Long extension cord? How long is long? The cord was rated for how
many amps?

What voltage & current did the drill require?

Michael
 
N

NG Neer

Jan 1, 1970
0
Long extension cord? How long is long? The cord was rated for how
many amps?
Over the 4 year life of the drill, I've used numerous different
extension cords. can't remember them all.

The drill is rated 6 amps @ 120 volt.

here's the link to the original article i was reffering to:
http://www.askthebuilder.com/174_Extension_Cords_-_Wrong_Size_Will_Hurt_Tools_.shtml

but my point is that it shouldn't matter how long the cord, or how
much the voltage drop, for these types of motors the lower voltage
would just result in lower RPM's. unless I'm missing something...
 
J

Jamie

Jan 1, 1970
0
NG said:
Over the 4 year life of the drill, I've used numerous different
extension cords. can't remember them all.

The drill is rated 6 amps @ 120 volt.

here's the link to the original article i was reffering to:
http://www.askthebuilder.com/174_Extension_Cords_-_Wrong_Size_Will_Hurt_Tools_.shtml

but my point is that it shouldn't matter how long the cord, or how
much the voltage drop, for these types of motors the lower voltage
would just result in lower RPM's. unless I'm missing something...
No it don't matter, you got screwed!. Cheap drill. Low brush level.
Crap speed control in trigger.
most of those use a electronic speed control and most are junk!.

http://webpages.charter.net/jamie_5"
 
J

Joerg

Jan 1, 1970
0
NG said:
I recently had a good quality corded drill fail after less than 4
years (see link for pictures/details). I just read that running such
tools with very long or thin extension cords can make them fail, due
to the voltage drop in the extension cord causing the motor to draw
excessive current.

I've always known that running an induction motor on low voltage
causes execssive current and overheating, but I don't see how that
could be the case for "universal" motors with commutators. I mean,
isn't that how the trigger varies the speed of the drill, by reducing
the voltage to the motor? Reduced voltage due to losses in your cord
should just make the drill run slower, unless am I missing something
here??

Nah, I brought a lot of 230V tools across the ocean during our move to
the US. They all run happily on 120V, just with a lot less oomph. In
fact, I sanded the paint off of our huge deck. The Bosch 230V electric
drill ran a sanding disk more or less 10h non-stop for several days.
This drill is now about 30 years old, never needed new brushes and I've
beaten the dickens out of that machine.



Hmm, and I though DeWalt is a good brand. Hmm ...
 
N

NG Neer

Jan 1, 1970
0
Hmm, and I though DeWalt is a good brand. Hmm ...

in all fairness, I must report that a rep from Dewalt called me about
12 hours after I emailed them**, and said they would mail out a new
switch to me, or I could bring the drill to one of their repair
centers for free repair. So I am still happy with Dewalt, hopefully
this switch failure was a fluke.

**I submitted by complaint via the standard email address on their
website, and got back a standard "only a repair center can determine
warranty elligibility... blah blahh". However, I also emailed a link
to my website to everyone on the Dewalt board of directors, and any
other dewalt (and black and decker) email addresses google dug up...
 
P

Phil Allison

Jan 1, 1970
0
"NG Neer"
here's the link to the original article i was reffering to:
http://www.askthebuilder.com/174_Extension_Cords_-_Wrong_Size_Will_Hurt_Tools_.shtml

but my point is that it shouldn't matter how long the cord, or how
much the voltage drop, for these types of motors the lower voltage
would just result in lower RPM's. unless I'm missing something...


** The story is complete bollocks, another dopey myth about failure
causation.

As you would expet from someone talking about something way outside his
field.



...... Phil
 
in all fairness, I must report that a rep from Dewalt called me about
12 hours after I emailed them**, and said they would mail out a new
switch to me, or I could bring the drill to one of their repair
centers for free repair. So I am still happy with Dewalt, hopefully
this switch failure was a fluke.

**I submitted by complaint via the standard email address on their
website, and got back a standard "only a repair center can determine
warranty elligibility... blah blahh". However, I also emailed a link
to my website to everyone on the Dewalt board of directors, and any
other dewalt (and black and decker) email addresses google dug up...


Smart! I have to remember that trick. Email the whole board of
directors... hmm...

Michael
 
P

PeterD

Jan 1, 1970
0
I recently had a good quality corded drill fail after less than 4
years (see link for pictures/details). I just read that running such
tools with very long or thin extension cords can make them fail, due
to the voltage drop in the extension cord causing the motor to draw
excessive current.

I've always known that running an induction motor on low voltage
causes execssive current and overheating, but I don't see how that
could be the case for "universal" motors with commutators. I mean,
isn't that how the trigger varies the speed of the drill, by reducing
the voltage to the motor? Reduced voltage due to losses in your cord
should just make the drill run slower, unless am I missing something
here??

link: http://mysite.verizon.net/rvotin/Dewalt_drill_failure.htm

Personally, I'd say voltage had little or nothing to do with the
failure. I see that Dewalt has done the 'right' thing, and you are
set...
 
J

Joerg

Jan 1, 1970
0
NG said:
in all fairness, I must report that a rep from Dewalt called me about
12 hours after I emailed them**, and said they would mail out a new
switch to me, or I could bring the drill to one of their repair
centers for free repair. So I am still happy with Dewalt, hopefully
this switch failure was a fluke.

**I submitted by complaint via the standard email address on their
website, and got back a standard "only a repair center can determine
warranty elligibility... blah blahh". However, I also emailed a link
to my website to everyone on the Dewalt board of directors, and any
other dewalt (and black and decker) email addresses google dug up...

I did the same with a Hamilton Beach blender that croaked after a dozen
uses. Was just over the warranty. They had chrome plated the shaft and
the plating had come off, clearly a mfg defect. After some email back
and forth they basically said "too bad, out of warranty, buy the spares"
which is almost the cost of a new blender with all the S&H fees. Last
time we ever bought that brand. The perfect method to erode a customer
base (there is a neighborhood here ...) and work up a poor reputation.
 
J

Jamie

Jan 1, 1970
0
NG said:
in all fairness, I must report that a rep from Dewalt called me about
12 hours after I emailed them**, and said they would mail out a new
switch to me, or I could bring the drill to one of their repair
centers for free repair. So I am still happy with Dewalt, hopefully
this switch failure was a fluke.
I don't think Fluke had anything to do with it unless their equipment
was being used in the engineering process! :)


http://webpages.charter.net/jamie_5"
 
J

Jamie

Jan 1, 1970
0
PeterD said:
Personally, I'd say voltage had little or nothing to do with the
failure. I see that Dewalt has done the 'right' thing, and you are
set...
Our guys at work use Dewalt cordless equipment, We find they last no
longer or are made any better than the average Sear's Crapmans drills.

There might have been a time where they did last but I think they all
now made in the same place!

It's just a name you're paying for.!

http://webpages.charter.net/jamie_5"
 
K

krw

Jan 1, 1970
0
PeterD wrote:

Our guys at work use Dewalt cordless equipment, We find they last no
longer or are made any better than the average Sear's Crapmans drills.

Depends on the Crapsman product. Some are relabeled DeWalts, but
that doesn't mean they're the same thing. I've long given up on
Crapsman tools (other than wrenches). I had a circular saw that
wouldn't cut a straight line. Forget the sabre saw. I've recently
bought a bunch of DeWalts because one of the BORGs here has put
ridiculous prices on them[*], at times.

[*] 12V driver/drill w/2 batteries for $50, 18V Heavy Duty Driver
Drill w/2 high capacity batteries for $100. ...cheaper than the
batteries alone.
There might have been a time where they did last but I think they all
now made in the same place!

Some are.
It's just a name you're paying for.!

Because they were made in the same place does not imply they are the
same product. Sears puts specs out to bid. Whoever meets those
specs...
 
J

Jamie

Jan 1, 1970
0
krw said:
PeterD wrote:



Our guys at work use Dewalt cordless equipment, We find they last no
longer or are made any better than the average Sear's Crapmans drills.


Depends on the Crapsman product. Some are relabeled DeWalts, but
that doesn't mean they're the same thing. I've long given up on
Crapsman tools (other than wrenches). I had a circular saw that
wouldn't cut a straight line. Forget the sabre saw. I've recently
bought a bunch of DeWalts because one of the BORGs here has put
ridiculous prices on them[*], at times.

[*] 12V driver/drill w/2 batteries for $50, 18V Heavy Duty Driver
Drill w/2 high capacity batteries for $100. ...cheaper than the
batteries alone.

There might have been a time where they did last but I think they all
now made in the same place!


Some are.

It's just a name you're paying for.!


Because they were made in the same place does not imply they are the
same product. Sears puts specs out to bid. Whoever meets those
specs...


We had to replace the batteries in each Dewalt device we got shortly
after we started to use them. A couple of them only lasted for 1 charge.
the next charge, the batteries were completely non responsive to a charge.
We found the recent 1/2 and 3/8 " drive cordless from Crapsman to
have the same problem. After ripping apart a couple we noticed that both
Crapmans
and Dewalts cells were the same ones. (Made in China)..

So, I don't know what to say how ever, I my self still have an older
larger crapsman cordless that still works and it has gone through hell.!

they stop making these of course. Most likely because they hold up to
well.



http://webpages.charter.net/jamie_5"
 
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