Electric Motor query - 3 phase /single phase
 

I'm thinking about getting a planer/thickenesser and paid a visit to a
local tool merchant who also deals in second hand equipment. He has a
machine that is the right size but has a 3 phase motor of 1.5kW. Now
it just happens that I've been given in the last couple of weeks a
fairly up-to-date 2kW single phase motor.

Forgetting about the possible mechanical problems of changing the
motors over, are there any other characteristics that are likely to
cause bother - I haven't looked at motor speeds yet but that is just
changing the pulley size. Will I have problems for instance at start
up as the planer will have a fair amount of inertia ?

Any comments gratefully received.

Rob

On 4 May 2005 15:00:36 -0700, wrote:

I'm thinking about getting a planer/thickenesser and paid a visit to a
local tool merchant who also deals in second hand equipment.

I'm no great fan of planer thicknessers. They're expensive and narrow,
compared to spending the same money on separate machines. The pressed
steel ones are wobbly enough I wouldn't like to buy one S/H, the cast
iron ones are heavy and awkward to convert between modes

He has a machine that is the right size

What is it ?

but has a 3 phase motor of 1.5kW. Now
it just happens that I've been given in the last couple of weeks a
fairly up-to-date 2kW single phase motor.

The old wood-working machines site is worth a look. www.owwm.com
Particularly the electricals section of the FAQ

Forgetting about the possible mechanical problems of changing the
motors over, are there any other characteristics that are likely to
cause bother

Mechanical problems shouldn't be underestimated. Belt sections are no
longer the same as a few years ago, nor are the spacings for multi-belt
drives. Even motor shafts are likely to have changed diameter from
imperial to metric. Last time I did this I had to replace the triple
pulley to fit one with a taperloc bush to fit the new shaft, and even an
approximately suitable pulley had to be ordered in and cost as much as a
small motor

You'll probably need a new starter, as old ones are often less than
ideal. It must be a no-volt release type and should be a proper
contactor with separate control switches, not one of those awful
American hold-in magnetic switches. It _must_ be of a suitable rating
for the motor and it should have the overload trip adjusted for an
appropriate current. Most 3 phase starters are usable on single phase,
but the overload calibration needs to be appropriate.

If you buy a starter from mail-order toolshops, get one from Axminster,
not Machine Mart or Screwfix. While you're about it, you can also fit
knee switches to stop it and you should fit a separate rotary or cam
isolator switch.

The PUWER 98 regs may apply to you, depending on where you site this
machine (and whether it's sold as working kit). It's possible you might
even need to install (very expensive) electric braking on it.
http://www.hse.gov.uk/pubns/woodindx.htm

- I haven't looked at motor speeds yet

Shouldn't have changed. Everything is either 3400 or 1725rpm, so you've
an even chance of it just working right.

Will I have problems for instance at start
up as the planer will have a fair amount of inertia ?

Shouldn't be any problem - it will take a little longer to come up to
speed on single phase, but not so you'd notice.

--
Cats have nine lives, which is why they rarely post to Usenet.

This is amateur land we're in so regulations - weIl was going to say
'don't apply' - what I probably mean is 'can be ignored' , and although
not 'certified', I'm a competent electrician. Also time is not
important but space is so a P/T it has to be.

A days poking around and asking has led me to looking at a 1.5kW
convertor which is available to =A3150+ and may be a far simpler and
speedier approach, with the advantage that the machine is sellable
without any modification.

Thanks very much for your full reply - you have covered just about
everything I needed.

Rob

On 5 May 2005 14:04:07 -0700, wrote:

A days poking around and asking has led me to looking at a 1.5kW
convertor which is available to ñ50+

If you're thinking of phase conversion, then definitely read the OWWM
site.

I'd use an idler motor if I couldn't convert the motor easily, but
static phase converters (capacitor boxes) are a total PITA.

--
Cats have nine lives, which is why they rarely post to Usenet.

"Andy Dingley" wrote in message
...
On 5 May 2005 14:04:07 -0700, wrote:

A days poking around and asking has led me to looking at a 1.5kW
convertor which is available to ñ50+

If you're thinking of phase conversion, then definitely read the OWWM
site.

I'd use an idler motor if I couldn't convert the motor easily, but
static phase converters (capacitor boxes) are a total PITA.


I totally agree on the point of converters being a total pain in the
proverbial. I'd much rather go for a good induction motor than use a
converter. :-)