On Sep 30, 2:39*pm, Gunner wrote:
On Sat, 29 Sep 2012 22:32:45 -0500, Ignoramus23622





wrote:
On 2012-09-30, Jon Elson wrote:
Ignoramus23622 wrote:

I have several electric motor-like things, they are called
motor-generators. It is a motor paired to a generator.

If this has 400 Hz output, the aviation folks might be interested,
although 100 Hp is probably more than they need. *There are places
that run really heavy 400-Hz loads, however, such as where NASA
runs air force radar dishes for tracking radars and telemetry.

Just a thought,

Jon

NASA would not buy from me, that's the problem.

But..a NASA supplier would buy from you.

They would then take it, recert it..and then sell it to NASA

Gunner

Liberals - Cosmopolitan critics, men who are the friends
of every country save their own. Benjamin Disraeli- Hide quoted text -

- Show quoted text -

Hey Gummer...how come Ig is successful in surplus while you starving
at it, years behind on taxes and owing everyone alive?

May be being a conservative doesn't pay well?

TMT

Make a DC power supply. The 400 Hz makes clean DC - but be
very very careful!!!!! 400 Hz is not a skin effect frequency like 60
cycle. 400 hz is center of the core - and will burn out marrow in your
arms if you short out an arm.

That happened to my Dad when they were looking at 400 for Ships. They
stuck with 60 cycle as they needed the ballast. Aircraft went to 400.

Martin

On 9/30/2012 8:01 AM, Ignoramus6882 wrote:
On 2012-09-30, Larry Jaques wrote:
On Sat, 29 Sep 2012 22:09:32 -0500, Ignoramus23622
wrote:

On 2012-09-30, Richard wrote:
On 9/29/2012 8:36 PM, Ignoramus23622 wrote:
I have several electric motor-like things, they are called
motor-generators. It is a motor paired to a generator.

For scrap purposes, they are both electric motors. They are about 100
HP in size.

I bought them as complete units and I expect that I will be scrapping
them and selling off contactors and such.

When I look up prices of "scrap electric motors", I only see prices
published for fractional horsepower motors.

My question is, are large motors valued at a higher price per lb, or
lower, than fractional motors.

The total weight of these devices is 14,000 lbs, so I better do a good
research before selecting a particular scrap yard.

i

If it works (?) it's worth a hell of a lot more than scrap value!


Who needs a 100 HP motor generator making 417 Hertz?

Someone making a hybrid electric bus?

Find an avionics client?

I got a grand last night from the golf cart my neighbor gave to me. I
had lots of expenses in repair, though: $4.95 for a 10" battery cable.

Recycling is good!


Awesome! This kind of stuff is what makes life fun!

In this case, I would need to find a user of an old IBM mainframe who
needs a 415 Hz power supply. Which is not something that I hold my
breath for.

http://ieeexplore.ieee.org/xpl/login...number%3D44248


i

On 2012-10-01, Martin Eastburn wrote:
Make a DC power supply. The 400 Hz makes clean DC - but be
very very careful!!!!! 400 Hz is not a skin effect frequency like 60
cycle. 400 hz is center of the core - and will burn out marrow in your
arms if you short out an arm.

There are many better ways of makign DC power supplies, I think.

i
That happened to my Dad when they were looking at 400 for Ships. They
stuck with 60 cycle as they needed the ballast. Aircraft went to 400.

Martin

On 9/30/2012 8:01 AM, Ignoramus6882 wrote:
On 2012-09-30, Larry Jaques wrote:
On Sat, 29 Sep 2012 22:09:32 -0500, Ignoramus23622
wrote:

On 2012-09-30, Richard wrote:
On 9/29/2012 8:36 PM, Ignoramus23622 wrote:
I have several electric motor-like things, they are called
motor-generators. It is a motor paired to a generator.

For scrap purposes, they are both electric motors. They are about 100
HP in size.

I bought them as complete units and I expect that I will be scrapping
them and selling off contactors and such.

When I look up prices of "scrap electric motors", I only see prices
published for fractional horsepower motors.

My question is, are large motors valued at a higher price per lb, or
lower, than fractional motors.

The total weight of these devices is 14,000 lbs, so I better do a good
research before selecting a particular scrap yard.

i

If it works (?) it's worth a hell of a lot more than scrap value!


Who needs a 100 HP motor generator making 417 Hertz?

Someone making a hybrid electric bus?

Find an avionics client?

I got a grand last night from the golf cart my neighbor gave to me. I
had lots of expenses in repair, though: $4.95 for a 10" battery cable.

Recycling is good!


Awesome! This kind of stuff is what makes life fun!

In this case, I would need to find a user of an old IBM mainframe who
needs a 415 Hz power supply. Which is not something that I hold my
breath for.

http://ieeexplore.ieee.org/xpl/login...number%3D44248


i

Ignoramus6882 wrote:



In this case, I would need to find a user of an old IBM mainframe who
needs a 415 Hz power supply. Which is not something that I hold my
breath for.
No, nobody is running that old gear. The Computer History Museum
might have such a machine, but it is extremely unlikely they would
try to run it, due to the power and air conditioning needs.

But, the aviation shops need modest amounts of 400 Hz power
to test all sorts of gear still in use. Depending on the
size of whatever they are testing, they could need multi-KW
amounts of 400 Hz 3-phase power. Basically, on commercial
and military aircraft, anything that uses over 1 KW runs off the
AC power system, and there's a HELL of a lot of loads in them.

Jon

Ignoramus23622 wrote:



NASA would not buy from me, that's the problem.
How do you know? If they have a million $ radar disk
and it needs a new frequency converter, I bet they might
buy from you, or anybody that had the right parts to keep it
running. I KNOW NASA is running a whole island full of
stuff they got from the Air Force from the DEW project
or something of similar date (late 50's to early 60's).
I'm sure they have maintenance headaches with that old
stuff. How you'd get in touch with them is another
story, of course. And, you never know when they's actually
NEED such an item. So, it was just a suggestion that
there ARE some outfits that actually have a use for gear
like that.

Jon

Michael A. Terrell wrote:



Did you ever see any Microdyne or L3-Com telemetry receivers?
Mostly Nems-Clarke when I was there, which was 40 years ago.
I worked a summer for Defense Electronics Inc. which bought out
the Nems-Clarke name and most of the products from Vitro, I think.

I got to ride in the cab of the Advanced Data Acquisition System
while boresighting a CCTV camera. That one was an old Air Force
radar disk and was definitely run off 400 Hz hydraulics. I think
it was 60' diameter. Looks like they might have torn this down.

Jon

Ignoramus6882 wrote:

On 2012-09-30, wrote:


Since they are made by Kato, I doubt there is any way to separate the
motor part from the generator part.


While I will soon know for sure, this is indeed what I expect, that
they are closely coupled.

The GE motor-alternator sets on the IBM 370/145 were 2-bearing
affairs. The motor and alternator sections were separate, but the
whole thing was on one shaft with two end bells, and both stators
in the same housing between them. A guy I know cut the motor rotor
off the shaft and rigged it by belts to a VW engine to make a
400 Hz TIG system. The 370/145 had a 17 KVA alternator output.

Jon

AFAIK, the ground power at the airport gate is 208 wye 400 Hz.
See ISO 6858.

For example, the 787 has three 90KVA connections.
http://www.boeing.com/commercial/aeromagazine/articles/qtr_3_08/pdfs/AERO_Q308_article2.pdf
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Jon Elson wrote:

Michael A. Terrell wrote:


Did you ever see any Microdyne or L3-Com telemetry receivers?
Mostly Nems-Clarke when I was there, which was 40 years ago.
I worked a summer for Defense Electronics Inc. which bought out
the Nems-Clarke name and most of the products from Vitro, I think.

I got to ride in the cab of the Advanced Data Acquisition System
while boresighting a CCTV camera. That one was an old Air Force
radar disk and was definitely run off 400 Hz hydraulics. I think
it was 60' diameter. Looks like they might have torn this down.


Microdyne was started by two engineers & a salesman who left Defense
Electronics about that time. One receiver at the cape had been in
continuous use for 30 years in 2000.

On 9/30/2012 7:56 PM, Ignoramus6882 wrote:
On 2012-10-01, wrote:
....

Cut the windings out and sell the copper separately from the frames.
You will get more for the copper alone tnan for the entire M-G sets -
and still have the steel left. Cases are likely maleable iron - which
has different value than steel - and is worth more separated than
mixed.

But it costs money to separate. Last time I looked at parting out
motor windings, it seemed difficult.

Yeah, but something that's 14k lb instead of 200 _may_ make it worth it;
I don't know. Cu is down from peak altho still pricey and I don't know
what the knockdown for the windings being coated rather than just copper
is but surely is worth checking on I'd think...

And, as said above you don't have to disassemble as for repair...

Just $0.01, etc., etc., etc., ...

--

On 2012-10-01, Jon Elson wrote:
Ignoramus6882 wrote:



In this case, I would need to find a user of an old IBM mainframe who
needs a 415 Hz power supply. Which is not something that I hold my
breath for.
No, nobody is running that old gear. The Computer History Museum
might have such a machine, but it is extremely unlikely they would
try to run it, due to the power and air conditioning needs.

But, the aviation shops need modest amounts of 400 Hz power
to test all sorts of gear still in use. Depending on the
size of whatever they are testing, they could need multi-KW
amounts of 400 Hz 3-phase power. Basically, on commercial
and military aircraft, anything that uses over 1 KW runs off the
AC power system, and there's a HELL of a lot of loads in them.

Jon

But they have no use for 415 hz, do they?

On 2012-10-01, Jon Elson wrote:
Ignoramus6882 wrote:

On 2012-09-30, wrote:


Since they are made by Kato, I doubt there is any way to separate the
motor part from the generator part.


While I will soon know for sure, this is indeed what I expect, that
they are closely coupled.

The GE motor-alternator sets on the IBM 370/145 were 2-bearing
affairs. The motor and alternator sections were separate, but the
whole thing was on one shaft with two end bells, and both stators
in the same housing between them. A guy I know cut the motor rotor
off the shaft and rigged it by belts to a VW engine to make a
400 Hz TIG system. The 370/145 had a 17 KVA alternator output.

Jon

Yeah, doubtfully anyone would want to pay above scrap price for a
project like this.

i

On 2012-10-01, dpb wrote:
On 9/30/2012 7:56 PM, Ignoramus6882 wrote:
On 2012-10-01, wrote:
...

Cut the windings out and sell the copper separately from the frames.
You will get more for the copper alone tnan for the entire M-G sets -
and still have the steel left. Cases are likely maleable iron - which
has different value than steel - and is worth more separated than
mixed.

But it costs money to separate. Last time I looked at parting out
motor windings, it seemed difficult.

Yeah, but something that's 14k lb instead of 200 _may_ make it worth it;
I don't know. Cu is down from peak altho still pricey and I don't know
what the knockdown for the windings being coated rather than just copper
is but surely is worth checking on I'd think...

And, as said above you don't have to disassemble as for repair...

Just $0.01, etc., etc., etc., ...

--

I agree, I will give this question my utmost attention, maybe there is
some easy way of doing it. And larger windings are easier to deal with
than small windings.

i

Ignoramus350 wrote:



Yeah, doubtfully anyone would want to pay above scrap price for a
project like this.
ONLY if they actually NEED such a unit, but if the DO need it, they
might need it really badly, like to get a major computer, radar
or whatever back on line. I doubt there are too many places that
have this kind of gear available. So, not a really big chance
you can find a buyer who needs exactly that unit, right now,
but sure worth a quick check.

Jon

Ignoramus350 wrote:

On 2012-10-01, Jon Elson wrote:
Ignoramus6882 wrote:



In this case, I would need to find a user of an old IBM mainframe who
needs a 415 Hz power supply. Which is not something that I hold my
breath for.
No, nobody is running that old gear. The Computer History Museum
might have such a machine, but it is extremely unlikely they would
try to run it, due to the power and air conditioning needs.

But, the aviation shops need modest amounts of 400 Hz power
to test all sorts of gear still in use. Depending on the
size of whatever they are testing, they could need multi-KW
amounts of 400 Hz 3-phase power. Basically, on commercial
and military aircraft, anything that uses over 1 KW runs off the
AC power system, and there's a HELL of a lot of loads in them.

Jon

But they have no use for 415 hz, do they?
415 Hz is 3.75% high, I can't believe the aircraft systems would
care. On the old planes (anything from F-4 to Boeing 707 to
pretty modern) they used multiple alternators that were driven
by hydraulic constant-speed drives. The alternators were
hard-synched, ie. they were just connected
to a couple common busses. When they start the engines on a passenger
jet and you see the lights blink, that is the alternators being added to the
bus. So, these constant-speed drives were very soft, to allow multiple
alternators to be synched, and I'd guess frequency varies by 5 - 10%
normally depending on load and the number of alternators supplying
the bus.

So, I am pretty sure any aviation maintenance outfit would find 415
Hz to be quite OK for testing aircraft hardware. The specific voltages
used on different planes were different, but 120/208 was pretty
common.

Jon

Ignoramus350 wrote:


I agree, I will give this question my utmost attention, maybe there is
some easy way of doing it. And larger windings are easier to deal with
than small windings.
It depends on how the motor was dipped. Some have relatively loose
windings, after cutting one end, you can drive the winding out of the
stator slot with little effort. On others, they are essentially
epoxy-potted, and the windings won't come out without roasting the entire
stator for days in an oven. And, then the EPA will come looking for
your hide.

My guess is the larger units are never made the potted way as the epoxy
just gets too expensive.

Jon

Michael A. Terrell wrote:


Jon Elson wrote:

Michael A. Terrell wrote:


Did you ever see any Microdyne or L3-Com telemetry receivers?
Mostly Nems-Clarke when I was there, which was 40 years ago.
I worked a summer for Defense Electronics Inc. which bought out
the Nems-Clarke name and most of the products from Vitro, I think.

I got to ride in the cab of the Advanced Data Acquisition System
while boresighting a CCTV camera. That one was an old Air Force
radar dish and was definitely run off 400 Hz hydraulics. I think
it was 60' diameter. Looks like they might have torn this down.


Microdyne was started by two engineers & a salesman who left Defense
Electronics about that time. One receiver at the cape had been in
continuous use for 30 years in 2000.
Yeah, that was REALLY well-built stuff, I sometimes see some some
Watkins-Johnson, Nems-Clarke and such show up on eBay, usually badly
incomplete, and still for serious money. Wouldn't mind having a
Nems-Clarke receiver with a set of front ends and the spectrum
analyzer (panoramic display), but buying one piece and hoping the
rest show up someday might be a bad plan.

Jon

On Sep 29, 7:36*pm, Ignoramus23622 ignoramus23...@NOSPAM.
23622.invalid wrote:
I have several electric motor-like things, they are called
motor-generators. It is a motor paired to a generator.

For scrap purposes, they are both electric motors. They are about 100
HP in size.

I bought them as complete units and I expect that I will be scrapping
them and selling off contactors and such.

When I look up prices of "scrap electric motors", I only see prices
published for fractional horsepower motors.

My question is, are large motors valued at a higher price per lb, or
lower, than fractional motors.

The total weight of these devices is 14,000 lbs, so I better do a good
research before selecting a particular scrap yard.

i

Most motors that size are worth breaking down to separate the copper
out. Fractional horsepower stuff, not so much, which is why only a
few cents a pound for them. Knew one scrap dealer that accumulated
barrels of motors during good weather and scrapped them out during the
winter when he couldn't work out in the yard. Probably could use a
sawzall on your big stuff to cut tie bands and such and maybe whack
the windings at the corners to get straight bits that you can get out
of the slots. The remains would go as regular steel scrap. Weigh the
amount of copper you get out of the first one to see if it would be a
paying deal.

Stan

On 2012-10-01, Jon Elson wrote:
Ignoramus350 wrote:

On 2012-10-01, Jon Elson wrote:
Ignoramus6882 wrote:



In this case, I would need to find a user of an old IBM mainframe who
needs a 415 Hz power supply. Which is not something that I hold my
breath for.
No, nobody is running that old gear. The Computer History Museum
might have such a machine, but it is extremely unlikely they would
try to run it, due to the power and air conditioning needs.

But, the aviation shops need modest amounts of 400 Hz power
to test all sorts of gear still in use. Depending on the
size of whatever they are testing, they could need multi-KW
amounts of 400 Hz 3-phase power. Basically, on commercial
and military aircraft, anything that uses over 1 KW runs off the
AC power system, and there's a HELL of a lot of loads in them.

Jon

But they have no use for 415 hz, do they?
415 Hz is 3.75% high, I can't believe the aircraft systems would
care. On the old planes (anything from F-4 to Boeing 707 to
pretty modern) they used multiple alternators that were driven
by hydraulic constant-speed drives. The alternators were
hard-synched, ie. they were just connected
to a couple common busses. When they start the engines on a passenger
jet and you see the lights blink, that is the alternators being added to the
bus. So, these constant-speed drives were very soft, to allow multiple
alternators to be synched, and I'd guess frequency varies by 5 - 10%
normally depending on load and the number of alternators supplying
the bus.

So, I am pretty sure any aviation maintenance outfit would find 415
Hz to be quite OK for testing aircraft hardware. The specific voltages
used on different planes were different, but 120/208 was pretty
common.

Jon

My driver brought them in today on the semi truck.

I just came to my shop after a day of travel and I looked at the
units.

I believe them to have approximately $2,200 worth of parts. There are
four size 3 C-H contactors, big circuit breakers, copper wire, and
motor-generators that weigh 2,200 lbs (estimate), per each unit.

To beat that, I will need to get a lot more money per unit on ebay,
since I need to store them, etc. Which I am not sure if I would get
that much.

They have hours on the hourmeters as follows: 00375, 24000, 53000,
84000, 92000.

I consider the first two possible candidates for resale, and the last
three I would part out right away.

i

On Mon, 01 Oct 2012 16:45:31 -0500, Jon Elson
wrote:

Ignoramus350 wrote:

On 2012-10-01, Jon Elson wrote:
Ignoramus6882 wrote:



In this case, I would need to find a user of an old IBM mainframe who
needs a 415 Hz power supply. Which is not something that I hold my
breath for.
No, nobody is running that old gear. The Computer History Museum
might have such a machine, but it is extremely unlikely they would
try to run it, due to the power and air conditioning needs.

But, the aviation shops need modest amounts of 400 Hz power
to test all sorts of gear still in use. Depending on the
size of whatever they are testing, they could need multi-KW
amounts of 400 Hz 3-phase power. Basically, on commercial
and military aircraft, anything that uses over 1 KW runs off the
AC power system, and there's a HELL of a lot of loads in them.

Jon

But they have no use for 415 hz, do they?
415 Hz is 3.75% high, I can't believe the aircraft systems would
care. On the old planes (anything from F-4 to Boeing 707 to
pretty modern) they used multiple alternators that were driven
by hydraulic constant-speed drives. The alternators were
hard-synched, ie. they were just connected
to a couple common busses. When they start the engines on a passenger
jet and you see the lights blink, that is the alternators being added to the
bus. So, these constant-speed drives were very soft, to allow multiple
alternators to be synched, and I'd guess frequency varies by 5 - 10%
normally depending on load and the number of alternators supplying
the bus.

So, I am pretty sure any aviation maintenance outfit would find 415
Hz to be quite OK for testing aircraft hardware. The specific voltages
used on different planes were different, but 120/208 was pretty
common.

Jon

I'll bet the generator outputs 415 Hz if the motor is running at
synchronous speed, which, assuming it's an induction motor, it never
does. In other words, the generator is nominally 415 Hz to account for
the motor's slip.

415 Hz / 400 Hz = 1800 RPM / 1715 RPM

--
Ned Simmons

On Mon, 01 Oct 2012 16:45:31 -0500, Jon Elson
wrote:

Ignoramus350 wrote:

On 2012-10-01, Jon Elson wrote:
Ignoramus6882 wrote:



In this case, I would need to find a user of an old IBM mainframe who
needs a 415 Hz power supply. Which is not something that I hold my
breath for.
No, nobody is running that old gear. The Computer History Museum
might have such a machine, but it is extremely unlikely they would
try to run it, due to the power and air conditioning needs.

But, the aviation shops need modest amounts of 400 Hz power
to test all sorts of gear still in use. Depending on the
size of whatever they are testing, they could need multi-KW
amounts of 400 Hz 3-phase power. Basically, on commercial
and military aircraft, anything that uses over 1 KW runs off the
AC power system, and there's a HELL of a lot of loads in them.

Jon

But they have no use for 415 hz, do they?
415 Hz is 3.75% high, I can't believe the aircraft systems would
care. On the old planes (anything from F-4 to Boeing 707 to
pretty modern) they used multiple alternators that were driven
by hydraulic constant-speed drives. The alternators were
hard-synched, ie. they were just connected
to a couple common busses. When they start the engines on a passenger
jet and you see the lights blink, that is the alternators being added to the
bus. So, these constant-speed drives were very soft, to allow multiple
alternators to be synched, and I'd guess frequency varies by 5 - 10%
normally depending on load and the number of alternators supplying
the bus.

So, I am pretty sure any aviation maintenance outfit would find 415
Hz to be quite OK for testing aircraft hardware. The specific voltages
used on different planes were different, but 120/208 was pretty
common.

Jon

The aircraft we're dealing with have fixed voltage but variable
frequency.

On 2012-10-01, Ned Simmons wrote:
On Mon, 01 Oct 2012 16:45:31 -0500, Jon Elson
wrote:

Ignoramus350 wrote:

On 2012-10-01, Jon Elson wrote:
Ignoramus6882 wrote:



In this case, I would need to find a user of an old IBM mainframe who
needs a 415 Hz power supply. Which is not something that I hold my
breath for.
No, nobody is running that old gear. The Computer History Museum
might have such a machine, but it is extremely unlikely they would
try to run it, due to the power and air conditioning needs.

But, the aviation shops need modest amounts of 400 Hz power
to test all sorts of gear still in use. Depending on the
size of whatever they are testing, they could need multi-KW
amounts of 400 Hz 3-phase power. Basically, on commercial
and military aircraft, anything that uses over 1 KW runs off the
AC power system, and there's a HELL of a lot of loads in them.

Jon

But they have no use for 415 hz, do they?
415 Hz is 3.75% high, I can't believe the aircraft systems would
care. On the old planes (anything from F-4 to Boeing 707 to
pretty modern) they used multiple alternators that were driven
by hydraulic constant-speed drives. The alternators were
hard-synched, ie. they were just connected
to a couple common busses. When they start the engines on a passenger
jet and you see the lights blink, that is the alternators being added to the
bus. So, these constant-speed drives were very soft, to allow multiple
alternators to be synched, and I'd guess frequency varies by 5 - 10%
normally depending on load and the number of alternators supplying
the bus.

So, I am pretty sure any aviation maintenance outfit would find 415
Hz to be quite OK for testing aircraft hardware. The specific voltages
used on different planes were different, but 120/208 was pretty
common.

Jon

I'll bet the generator outputs 415 Hz if the motor is running at
synchronous speed, which, assuming it's an induction motor, it never
does. In other words, the generator is nominally 415 Hz to account for
the motor's slip.

415 Hz / 400 Hz = 1800 RPM / 1715 RPM


That could be, also.

i

Ned Simmons wrote:



I'll bet the generator outputs 415 Hz if the motor is running at
synchronous speed, which, assuming it's an induction motor, it never
does. In other words, the generator is nominally 415 Hz to account for
the motor's slip.

415 Hz / 400 Hz = 1800 RPM / 1715 RPM

Nope, doesn't quite work out. The alternator has to have an integral
number of poles. To get 415 Hz at 1800 RPM it would need 13.333
poles. 14 poles and 1778.6 RPM (29.64 RPS) gives 415 Hz.
1779 RPM is reasonable for a larger 3-phase induction motor.
If your line voltage were a bit low, the slip would be greater, and
the motor would spin slower, although not by much. To get down to
400 hz the motor would need to spin at 28.57 RPS or 1714 RPM.
I doubt you could get it to slip that much without burning up the
motor rotor.

Jon

Ignoramus350 wrote:



To beat that, I will need to get a lot more money per unit on ebay,
since I need to store them, etc. Which I am not sure if I would get
that much.
Yeah, I certainly would not recommend hanging on to these beasts for
very long. If you don't find somebody quickly that needs such a unit,
the chance of one turning up later are really small. I was just mentioning
a couple industries that could use such a contraption.

If you go to the airport you'll see big boxes hanging under the
jetway ramps. One is an air conditioner for the plane. The other
is a combo 28 V DC power supply and either a motor-alternator set
or an electronic inverter.

Jon

On Mon, 01 Oct 2012 22:59:35 -0500, Jon Elson
wrote:

Ned Simmons wrote:



I'll bet the generator outputs 415 Hz if the motor is running at
synchronous speed, which, assuming it's an induction motor, it never
does. In other words, the generator is nominally 415 Hz to account for
the motor's slip.

415 Hz / 400 Hz = 1800 RPM / 1715 RPM

Nope, doesn't quite work out. The alternator has to have an integral
number of poles. To get 415 Hz at 1800 RPM it would need 13.333
poles. 14 poles and 1778.6 RPM (29.64 RPS) gives 415 Hz.
1779 RPM is reasonable for a larger 3-phase induction motor.
If your line voltage were a bit low, the slip would be greater, and
the motor would spin slower, although not by much. To get down to
400 hz the motor would need to spin at 28.57 RPS or 1714 RPM.
I doubt you could get it to slip that much without burning up the
motor rotor.

Jon

Yes, I probably should have said 415Hz unloaded instead of at
synchronous speed.

You left a factor of 2 out of the formula that relates relates the
number of motor poles to synchronous speed.

rps = 2f / P

But setting that aside, if the number of generator poles is 7x the
number of motor poles, and assuming a 4 pole motor, the frequency will
be 420Hz @ synchronous speed, 415Hz @ 1779 RPM, and 400Hz @ 1715 RPM.

Double the RPMs for a 2 pole motor, in which case the synchronous
speed is 3600 RPM.

A normal 3 phase motor might turn 1779 RPM with a very light load;
1750 - 1760 loaded is more typical, and 1725 RPM motors are common.
The difference between 1715 and 1725 is less than 1%. Motors with much
higher slip are available, but not necessary here, at least on paper.

--
Ned Simmons

On Sunday, 30 September 2012 02:36:55 UTC+1, Ignoramus23622 wrote:
I have several electric motor-like things, they are called

motor-generators. It is a motor paired to a generator.



For scrap purposes, they are both electric motors. They are about 100

HP in size.



I bought them as complete units and I expect that I will be scrapping

them and selling off contactors and such.



When I look up prices of "scrap electric motors", I only see prices

published for fractional horsepower motors.



My question is, are large motors valued at a higher price per lb, or

lower, than fractional motors.



The total weight of these devices is 14,000 lbs, so I better do a good

research before selecting a particular scrap yard.



i

Hi,

Do you still have these or have you scraped them?

Regards
keepsending786 at ho t mail co m