Hi all,

Last night I had chance to investigate my 2.5 hp motor in more depth.
There's good news and bad news, so I'll tell the story the way it happened.

First I removed the bearing covers and fan cowling. The ball races
appear sound and are still packed with grease. Peering into the stator
the windings look clean and shiny. There's a little rust on the rotor,
but this could easily be brushed off and painted over. The inside of the
motor is coated with this orange-red paint or resin, which looks a bit
like red oxide paint but isn't. I've seen it in motors before but I
don't know what it's called. Anyone know?

Next I opened the terminal box and removed all the links. I measured the
winding resistances with a multimeter. All are 6.5 ohms. There was no
measurable leakage between any winding and the motor casing. So far so
good. I now planned to connect a run capacitor and power up the motor
with no load, just to check everything worked. So I worked out the
correct link positions for a delta connection.

Aargh. Problem! The motor had originally been wired in a delta
connection. Of course 240 V is the line-to-neutral voltage of the UK's
three phase system, so I wondered (hopefully) if this motor had been
wired for 240 V three phase. But then I realised that there was no
neutral wire entering the terminal box, so it must have been wired for
415 V. Apologies Bob, you were right. Damn!

I've never seen a motor of this size which uses a delta connection for
415 V before. In fact, I don't think I've seen a motor below 10 hp which
uses a delta connection for 415 V. But I've never seen a motor of this
size with a fan cowling which weighs 20 lbs, or a rotor which is
fabricated from individual pieces of stock before, so I guess I
shouldn't be surprised. I guess in 1931 there may have been less export,
and it seems LSE specialised in large motors, so maybe a delta
connection was their standard?

On the plus side, this motor is a really cool piece of work. Had I known
it was 415 V only I would most likely have rescued it anyway rather than
letting it go to the landfill. I've got rather keen on the phase
converter idea, so it looks like I've now got the challenge of finding a
240 V - 415 V transformer with a rating of around 3 kVA. Anyone know of
likely sources? Jim Cox's books "Electric Motors" and "Electric Motors
in the Home Workshop" (which are a goldmine of practical information
about motors - Igor might like them if he hasn't got them already)
suggest modified old-fashioned welding transformers. I'm usually pretty
good at scrounging industrial junk, so if anyone can think of equipment
containing likely transformers please let me know!

A 415 V output is actually more useful than a 240 V output in the UK, as
I could then just wire a plug onto any equipment I buy and plug it into
the convertor. Almost all three phase equipment in the UK is wired for a
415 V line-to-line voltage. Jim Cox's books also note that smaller
capacitors are adequate for 415 V operation, so this setup has its
attractions. I doubt I'd want to run loads over 1.5 hp, so a carefully
designed convertor using a 2.5 hp idler should be okay. Food for
thought, anyway.

Sorry for the long post. I'd be interested to hear people's thoughts.

Best wishes,

Chris

On Sun, 7 Aug 2005 11:51:46 +0000 (UTC), Christopher Tidy
wrote:

SNIP
The inside of the
motor is coated with this orange-red paint or resin, which looks a bit
like red oxide paint but isn't. I've seen it in motors before but I
don't know what it's called. Anyone know?

Red Stuff is called Glyptol. Comes as paint or in a spray can. Made
in the US and Canada under General Electrics name.

Brian Lawson wrote:
On Sun, 7 Aug 2005 11:51:46 +0000 (UTC), Christopher Tidy
wrote:

SNIP

The inside of the
motor is coated with this orange-red paint or resin, which looks a bit
like red oxide paint but isn't. I've seen it in motors before but I
don't know what it's called. Anyone know?


Red Stuff is called Glyptol. Comes as paint or in a spray can. Made
in the US and Canada under General Electrics name.

Thanks. I will look out for some.

Chris

Christopher Tidy wrote:

Aargh. Problem! The motor had originally been wired in a delta
connection. Of course 240 V is the line-to-neutral voltage of the UK's
three phase system, so I wondered (hopefully) if this motor had been
wired for 240 V three phase. But then I realised that there was no
neutral wire entering the terminal box, so it must have been wired for
415 V. Apologies Bob, you were right. Damn!

It would be exceedingly uncommon to connect the neutral point of a
Wye-connected motor to neutral. In almost all cases, it is just taped
off.
I've never seen a motor of this size which uses a delta connection for
415 V before. In fact, I don't think I've seen a motor below 10 hp which
uses a delta connection for 415 V. But I've never seen a motor of this
size with a fan cowling which weighs 20 lbs, or a rotor which is
fabricated from individual pieces of stock before, so I guess I
shouldn't be surprised. I guess in 1931 there may have been less export,
and it seems LSE specialised in large motors, so maybe a delta
connection was their standard?

The data plate (earlier message) says 400 V, but seems to also say
"Star Delta" on the connection line. If you have 6 wires, you should
be able to (re)connect it in the star configuration for 230 V.

Jon

Jon Elson wrote:

snip

I've never seen a motor of this size which uses a delta connection for
415 V before. In fact, I don't think I've seen a motor below 10 hp
which uses a delta connection for 415 V. But I've never seen a motor
of this size with a fan cowling which weighs 20 lbs, or a rotor which
is fabricated from individual pieces of stock before, so I guess I
shouldn't be surprised. I guess in 1931 there may have been less
export, and it seems LSE specialised in large motors, so maybe a delta
connection was their standard?

The data plate (earlier message) says 400 V, but seems to also say
"Star Delta" on the connection line. If you have 6 wires, you should
be able to (re)connect it in the star configuration for 230 V.

That's what I thought, but I'm puzzled by the fact that the motor was
delta connected in its original factory installation. I would have
expected a motor of this size to be star connected for 415 V operation,
but I think it's unlikely that a factory in the UK would have a supply
with a 240 V line-to-line voltage. The only thing other thing I have to
go on is the winding resistance (6.5 ohms) but I can't see how this is a
help.

Apparently Laurence, Scott and Electromotors donated their early records
to the IEE library in London, so I could try there if all else fails.

Best wishes,

Chris

"Christopher Tidy" wrote in message
...
Hi all,

Last night I had chance to investigate my 2.5 hp motor in more depth.
There's good news and bad news, so I'll tell the story the way it
happened.

First I removed the bearing covers and fan cowling. The ball races
appear sound and are still packed with grease. Peering into the stator
the windings look clean and shiny. There's a little rust on the rotor,
but this could easily be brushed off and painted over. The inside of the
motor is coated with this orange-red paint or resin, which looks a bit
like red oxide paint but isn't. I've seen it in motors before but I
don't know what it's called. Anyone know?

Next I opened the terminal box and removed all the links. I measured the
winding resistances with a multimeter. All are 6.5 ohms. There was no
measurable leakage between any winding and the motor casing. So far so
good. I now planned to connect a run capacitor and power up the motor
with no load, just to check everything worked. So I worked out the
correct link positions for a delta connection.

Aargh. Problem! The motor had originally been wired in a delta
connection. Of course 240 V is the line-to-neutral voltage of the UK's
three phase system, so I wondered (hopefully) if this motor had been
wired for 240 V three phase. But then I realised that there was no
neutral wire entering the terminal box, so it must have been wired for
415 V. Apologies Bob, you were right. Damn!

I've never seen a motor of this size which uses a delta connection for
415 V before. In fact, I don't think I've seen a motor below 10 hp which
uses a delta connection for 415 V. But I've never seen a motor of this
size with a fan cowling which weighs 20 lbs, or a rotor which is
fabricated from individual pieces of stock before, so I guess I
shouldn't be surprised. I guess in 1931 there may have been less export,
and it seems LSE specialised in large motors, so maybe a delta
connection was their standard?

On the plus side, this motor is a really cool piece of work. Had I known
it was 415 V only I would most likely have rescued it anyway rather than
letting it go to the landfill. I've got rather keen on the phase
converter idea, so it looks like I've now got the challenge of finding a
240 V - 415 V transformer with a rating of around 3 kVA. Anyone know of
likely sources? Jim Cox's books "Electric Motors" and "Electric Motors
in the Home Workshop" (which are a goldmine of practical information
about motors - Igor might like them if he hasn't got them already)
suggest modified old-fashioned welding transformers. I'm usually pretty
good at scrounging industrial junk, so if anyone can think of equipment
containing likely transformers please let me know!

A 415 V output is actually more useful than a 240 V output in the UK, as
I could then just wire a plug onto any equipment I buy and plug it into
the convertor. Almost all three phase equipment in the UK is wired for a
415 V line-to-line voltage. Jim Cox's books also note that smaller
capacitors are adequate for 415 V operation, so this setup has its
attractions. I doubt I'd want to run loads over 1.5 hp, so a carefully
designed convertor using a 2.5 hp idler should be okay. Food for
thought, anyway.

Sorry for the long post. I'd be interested to hear people's thoughts.

Best wishes,

Chris

Chris
Rather than use it in reverse, I would suggest you use it as an auto
transformer by wiring 240V to the 240V on the primary winding and pick up
the 480V off the higher tap on the primary. I wouldn't want to run 240V into
the 120V winding if that's what you were planning to do as it may well
overheat.
My RPC has a 415V delta wound motor that can be wired 'Y' for a 660V supply
but it's a 10HP motor, although considerably smaller than your 2.5HP motor.
I had a transformer wound just for this RPC but it's fairly costly (£140 for
an 8KVA unit); you may well be in luck and find that the transformer on ebay
is multi-tapped and does have a 415V or 440V tap. I had to go the 415V route
as my mill cannot be rewired for 240V.
Good luck,
Martin
--
martindot herewhybrowat herentlworlddot herecom

Christopher Tidy wrote:
Jon Elson wrote:

snip

I've never seen a motor of this size which uses a delta connection
for 415 V before. In fact, I don't think I've seen a motor below 10
hp which uses a delta connection for 415 V. But I've never seen a
motor of this size with a fan cowling which weighs 20 lbs, or a rotor
which is fabricated from individual pieces of stock before, so I
guess I shouldn't be surprised. I guess in 1931 there may have been
less export, and it seems LSE specialised in large motors, so maybe a
delta connection was their standard?

The data plate (earlier message) says 400 V, but seems to also say
"Star Delta" on the connection line. If you have 6 wires, you should
be able to (re)connect it in the star configuration for 230 V.


That's what I thought, but I'm puzzled by the fact that the motor was
delta connected in its original factory installation. I would have
expected a motor of this size to be star connected for 415 V operation,
but I think it's unlikely that a factory in the UK would have a supply
with a 240 V line-to-line voltage. The only thing other thing I have to
go on is the winding resistance (6.5 ohms) but I can't see how this is a
help.

OOps, I think I got this backwards! I should have said :
If the STAR voltage is 400 V L-L(from the plate, not 415) then the
actual voltage across the individual windings would be 400/1.732 = 231
V. (1.732 is the square root of 3.) So, if this motor only has 3
windings, your only connection choices are delta or star. (Most motors
in the US are Wye only, with nine wires. There are 2 windings for each
phase. One set has an inaccessible center point, the other is wired
totally separately, so it can be connected in series with the other set
for high voltage, or parallel for low voltage. This is generally for
240 or 480 V systems. In the special case of 230/400 or 240/415 V
systems, you have the additional trick of the Delta/Wye conversion.

Jon

Chris

Since this is a fun/hobby project for you, I wonder if you'd consider it
worth the complexity to find a choke to put in series with the transformer.
If the choke was the right size to drop about 15 percent of the incoming
240vac, the 2 to 1 transformer would provide the required 415vac for your
idler.
It would be possible that a choke like this could be wound 'at home'
fairly easily, depending on your interest.

Jerry


"Christopher Tidy" wrote in message
...
Jon Elson wrote:

snip

I've never seen a motor of this size which uses a delta connection for
415 V before. In fact, I don't think I've seen a motor below 10 hp which
uses a delta connection for 415 V. But I've never seen a motor of this
size with a fan cowling which weighs 20 lbs, or a rotor which is
fabricated from individual pieces of stock before, so I guess I
shouldn't be surprised. I guess in 1931 there may have been less export,
and it seems LSE specialised in large motors, so maybe a delta
connection was their standard?

The data plate (earlier message) says 400 V, but seems to also say
"Star Delta" on the connection line. If you have 6 wires, you should
be able to (re)connect it in the star configuration for 230 V.

That's what I thought, but I'm puzzled by the fact that the motor was
delta connected in its original factory installation. I would have
expected a motor of this size to be star connected for 415 V operation,
but I think it's unlikely that a factory in the UK would have a supply
with a 240 V line-to-line voltage. The only thing other thing I have to go
on is the winding resistance (6.5 ohms) but I can't see how this is a
help.

Apparently Laurence, Scott and Electromotors donated their early records
to the IEE library in London, so I could try there if all else fails.

Best wishes,

Chris

Jerry Martes wrote:
Chris

Since this is a fun/hobby project for you, I wonder if you'd consider it
worth the complexity to find a choke to put in series with the transformer.
If the choke was the right size to drop about 15 percent of the incoming
240vac, the 2 to 1 transformer would provide the required 415vac for your
idler.
It would be possible that a choke like this could be wound 'at home'
fairly easily, depending on your interest.
But, an inductor will drop a voltage proportional to current. So, if
the load changes, the voltage drop will change, too. I really don't
think this will work, except under conditions of constant load.

Jon

On Mon, 08 Aug 2005 11:04:33 -0500, Jon Elson
wrote:

Jerry Martes wrote:
Chris

Since this is a fun/hobby project for you, I wonder if you'd consider it
worth the complexity to find a choke to put in series with the transformer.
If the choke was the right size to drop about 15 percent of the incoming
240vac, the 2 to 1 transformer would provide the required 415vac for your
idler.
It would be possible that a choke like this could be wound 'at home'
fairly easily, depending on your interest.
But, an inductor will drop a voltage proportional to current. So, if
the load changes, the voltage drop will change, too. I really don't
think this will work, except under conditions of constant load.

Jon


Small 24 or 28v transformers are pretty common items. A 24 or
28v secondary, connected in buck with the 240 in will give a
consistent 10 or 12% voltage drop which is probably near enough.

Jim

wrote:
On Mon, 08 Aug 2005 11:04:33 -0500, Jon Elson
wrote:


Jerry Martes wrote:

Chris

Since this is a fun/hobby project for you, I wonder if you'd consider it
worth the complexity to find a choke to put in series with the transformer.
If the choke was the right size to drop about 15 percent of the incoming
240vac, the 2 to 1 transformer would provide the required 415vac for your
idler.
It would be possible that a choke like this could be wound 'at home'
fairly easily, depending on your interest.

But, an inductor will drop a voltage proportional to current. So, if
the load changes, the voltage drop will change, too. I really don't
think this will work, except under conditions of constant load.

Jon



Small 24 or 28v transformers are pretty common items. A 24 or
28v secondary, connected in buck with the 240 in will give a
consistent 10 or 12% voltage drop which is probably near enough.

Jim

Thanks for the suggestion. It's an interesting idea and I'll give it
some thought. I'm taking some time to think over the options anyway
while I work on other things - fortunately there's no hurry! An
interesting development is that I have the option of two 2 kVA 230 V -
110 V transformers. These are ex-factory units designed to run
continuously and are enclosed in a steel box about 12" cube. The core
fills most of the box. I think these things are pretty conservatively
rated. Anyway, they are the old-fashioned type which can be dismantled,
and I was wondering about removing the primary and replacing it with a
185 V additive overwind to give me an autotransformer with an output of
415 V. Any thoughts?

Thanks for the help,

Chris

On Mon, 8 Aug 2005 21:07:47 +0000 (UTC), Christopher Tidy
wrote:

snip

Small 24 or 28v transformers are pretty common items. A 24 or
28v secondary, connected in buck with the 240 in will give a
consistent 10 or 12% voltage drop which is probably near enough.

Jim

Thanks for the suggestion. It's an interesting idea and I'll give it
some thought. I'm taking some time to think over the options anyway
while I work on other things - fortunately there's no hurry! An
interesting development is that I have the option of two 2 kVA 230 V -
110 V transformers. These are ex-factory units designed to run
continuously and are enclosed in a steel box about 12" cube. The core
fills most of the box. I think these things are pretty conservatively
rated. Anyway, they are the old-fashioned type which can be dismantled,
and I was wondering about removing the primary and replacing it with a
185 V additive overwind to give me an autotransformer with an output of
415 V. Any thoughts?

Thanks for the help,

Chris

The rewound secondary in auto transformer connection should
result in 4KVA continuous rating which is more than enough for your
application.

With 2 transformers, 110v from one, 75v from the other in
auto transformer connection yields over 7KVA. It bit wasteful but it's
now only necessary to remove a few turns and doesn't need a full
secondary rewind

You shouldn't need this, but an often overlooked kludge
is that quite a small fan will substantially uplift the long term
rating of a power transformer - something like 50% is possible.

Jim

wrote:
On Mon, 8 Aug 2005 21:07:47 +0000 (UTC), Christopher Tidy
wrote:

snip

Small 24 or 28v transformers are pretty common items. A 24 or
28v secondary, connected in buck with the 240 in will give a
consistent 10 or 12% voltage drop which is probably near enough.

Jim

Thanks for the suggestion. It's an interesting idea and I'll give it
some thought. I'm taking some time to think over the options anyway
while I work on other things - fortunately there's no hurry! An
interesting development is that I have the option of two 2 kVA 230 V -
110 V transformers. These are ex-factory units designed to run
continuously and are enclosed in a steel box about 12" cube. The core
fills most of the box. I think these things are pretty conservatively
rated. Anyway, they are the old-fashioned type which can be dismantled,
and I was wondering about removing the primary and replacing it with a
185 V additive overwind to give me an autotransformer with an output of
415 V. Any thoughts?

Thanks for the help,

Chris


The rewound secondary in auto transformer connection should
result in 4KVA continuous rating which is more than enough for your
application.

With 2 transformers, 110v from one, 75v from the other in
auto transformer connection yields over 7KVA. It bit wasteful but it's
now only necessary to remove a few turns and doesn't need a full
secondary rewind

You shouldn't need this, but an often overlooked kludge
is that quite a small fan will substantially uplift the long term
rating of a power transformer - something like 50% is possible.

Thanks for the advice. It sounds like these transformers would be ideal
for the project.

I studied transformers at university but my recollection of the theory
is now a little fuzzy. Why does the rewound secondary in auto
transformer connection permit a 4 kVA rating? I'll dig out my notes and
refresh my memory before starting the project in earnest.

Best wishes,

Chris

On Tue, 9 Aug 2005 22:23:14 +0000 (UTC), Christopher Tidy
wrote:

wrote:
On Mon, 8 Aug 2005 21:07:47 +0000 (UTC), Christopher Tidy
wrote:

snip

Small 24 or 28v transformers are pretty common items. A 24 or
28v secondary, connected in buck with the 240 in will give a
consistent 10 or 12% voltage drop which is probably near enough.

Jim

Thanks for the suggestion. It's an interesting idea and I'll give it
some thought. I'm taking some time to think over the options anyway
while I work on other things - fortunately there's no hurry! An
interesting development is that I have the option of two 2 kVA 230 V -
110 V transformers. These are ex-factory units designed to run
continuously and are enclosed in a steel box about 12" cube. The core
fills most of the box. I think these things are pretty conservatively
rated. Anyway, they are the old-fashioned type which can be dismantled,
and I was wondering about removing the primary and replacing it with a
185 V additive overwind to give me an autotransformer with an output of
415 V. Any thoughts?

Thanks for the help,

Chris


The rewound secondary in auto transformer connection should
result in 4KVA continuous rating which is more than enough for your
application.

With 2 transformers, 110v from one, 75v from the other in
auto transformer connection yields over 7KVA. It bit wasteful but it's
now only necessary to remove a few turns and doesn't need a full
secondary rewind

You shouldn't need this, but an often overlooked kludge
is that quite a small fan will substantially uplift the long term
rating of a power transformer - something like 50% is possible.

Thanks for the advice. It sounds like these transformers would be ideal
for the project.

I studied transformers at university but my recollection of the theory
is now a little fuzzy. Why does the rewound secondary in auto
transformer connection permit a 4 kVA rating? I'll dig out my notes and
refresh my memory before starting the project in earnest.

Best wishes,

Chris


Look at it in a slightly different way.

For the 1:1 ratio case think of a 1KVA 100V secondary that sits
on top of a 100V supply live. For its 1KVA rating this delivers 10A.
The return connection for this 10A current runs through the supply
which adds 100V to the delivered output so the load sees 200V at 10A
= 2KVA.

An easy way of working out the autotransformer connected
rating is to simply add the secondary volts to the supply volts and
multiply this by the rated secondary current.

Jim