I'm in the process of finally getting a rotary 3 phase converter going with
a BIG pilot motor but I'm confused by the motor rating. It's a 4kW 2850RPM
Brook Crompton motor to BS5000, frame 3D112MD, serial D102709, 415 delta
(symbol), rating MC, design 2E.

The bit that I'm not sure about is whether to leave it delta or re-connect
it as star (there are 6 terminals so it's easy to change). My limited
understanding was that: smaller motors would normally be wired star for 415
and delta for 230 (eg with an inverter); larger ones would normally be
started in star and then switched to delta (or the other way around if max
starting torque was required).
With a converter there is negligible starting torque needed so I would guess
that star would be the answer BUT when the load motor is started I assume a
lower source impedance would be good and therefore a delta pilot might be
better. Aaargh - onset of brain fade.

The motor is marked "4kW, 415 delta" will it still act as a 4kW motor if
wired in star?
Which is best for a converter, star or delta?
Can anyone decode the rating, design and frame codes?

Dave S

Dave wrote:

The motor is marked "4kW, 415 delta" will it still act as a 4kW motor if
wired in star?
Which is best for a converter, star or delta?

You need to match the (running) voltage rating of the motor to the
output of your converter. The voltage quoted for 3-ph systems is always
the line voltage (voltage between phases) unless stated otherwise.

If the rating plate says 415V delta, the motor would require a line
voltage of 720V if wired in star. So leave it wired in delta unless
you're planning to use a star-delta starter. If your converter only
produces 230V line - as some variable speed drives with single phase
inputs do, I believe - then you're stuffed (or need a 3-ph
auto-transformer).

Can anyone decode the rating, design and frame codes?

Try http://www.brookcrompton.com/ and look for technical support.

--
Andy

"Andy Wade" wrote in message
...
Dave wrote:
The motor is marked "4kW, 415 delta" will it still act as a 4kW motor if
wired in star?
Which is best for a converter, star or delta?

You need to match the (running) voltage rating of the motor to the
output of your converter. The voltage quoted for 3-ph systems is always
the line voltage (voltage between phases) unless stated otherwise.

If the rating plate says 415V delta, the motor would require a line
voltage of 720V if wired in star. So leave it wired in delta unless
you're planning to use a star-delta starter. If your converter only
produces 230V line - as some variable speed drives with single phase
inputs do, I believe - then you're stuffed (or need a 3-ph
auto-transformer).

I'm using a single phase auto to generate 415 and then capacitors and the
pilot motor to generate the 3rd phase. It seems to run OK in star but when I
connect the load motor (2HP) it has a marked effect on the pilot, when I run
the pilot in delta it pops a 13A fuse at start up.

Can anyone decode the rating, design and frame codes?
Try http://www.brookcrompton.com/ and look for technical support.

I looked here earlier but couldn't find any decodes (or even a tech support
section)

Dave S

Dave wrote:

I'm using a single phase auto to generate 415 and then capacitors and the
pilot motor to generate the 3rd phase. It seems to run OK in star but when I
connect the load motor (2HP) it has a marked effect on the pilot, when I run
the pilot in delta it pops a 13A fuse at start up.

I can't really follow that, but it sounds as if you haven't got a proper
converter and are trying to use some sort of lash-up with a second
motor(?). Some success at doing that was reported here a while ago, but
it all sounded rather hairy. If you do a Google groups search with the
search string as "3-phase motor group:uk.d-i-y author:andy authorugh"
you'll find plenty to read.

I suggest getting either a single-phase motor or a proper static converter.

BTW, if you're trying to run a 4 kW (3 HP) motor via a 13 A fuse it's
not surprising the fuse blows at start-up! For motors of that size you
want a dedicated circuit with (say) a 32A fuse for s/c protection, and
an overload relay in the starter for overload protection.

Try http://www.brookcrompton.com/ and look for technical support.

I looked here earlier but couldn't find any decodes (or even a tech support
section)

No, but under "worldwide service" you can find a UK telephone number to
ring.

--
Andy

"Andy Wade" wrote in message
...
Dave wrote:
I'm using a single phase auto to generate 415 and then capacitors and
the
pilot motor to generate the 3rd phase. It seems to run OK in star but
when I
connect the load motor (2HP) it has a marked effect on the pilot, when I
run
the pilot in delta it pops a 13A fuse at start up.
I can't really follow that, but it sounds as if you haven't got a proper
converter and are trying to use some sort of lash-up with a second
motor(?).

I'm converting a static converter to a rotary converter by adding a large
pilot motor.

Some success at doing that was reported here a while ago, but
it all sounded rather hairy. If you do a Google groups search with the
search string as "3-phase motor group:uk.d-i-y author:andy authorugh"
you'll find plenty to read.

Thanks for the pointer, I'll have a look

I suggest getting either a single-phase motor or a proper static
converter.

Single phase isn't an option (the primary load motor is 2HP, 3 speed and
buried deeply in the bowels of a lathe, there's also the coolant pump); I'm
converting a static converter to a rotary converter by adding a pilot motor.

BTW, if you're trying to run a 4 kW (3 HP) motor via a 13 A fuse it's
not surprising the fuse blows at start-up! For motors of that size you
want a dedicated circuit with (say) a 32A fuse for s/c protection, and
an overload relay in the starter for overload protection.

The pilot motor is running at zero load, just acting as a rotary
transformer; running current (admittedly in star) is just under 1A/ph.

Try http://www.brookcrompton.com/ and look for technical support.

I looked here earlier but couldn't find any decodes (or even a tech
support
section)
No, but under "worldwide service" you can find a UK telephone number to
ring.

--
Andy

If anybody is interested in following this I asked on
uk.rec.models.engineering and there's been a good discussion

Dave S