Oops, I thought the original motor was 3hp. Do verify that both 3 phase
and single are the same speeds, a lot of older 3 phase are 1750, smaller
single phase tend to be 3450 rpm.

Smaller pulley on the motor cuts down the required starting torque,
runpower requirements, lets it run cooler and quieter. Cuts down the
air output as well.

Ignoramus6689 wrote:

On Tue, 09 Aug 2005 14:41:00 GMT, RoyJ wrote:

Single phase. Why would anyone chose a 3 phase motor versus single if
they have to run a converter?


Well, my thought was, it would be nice for someone to get a nice shop
setup: a phase converter plus a compressor, all running, in a single
package local pickup deal.


And if you have 3 phase, you don't need the converter. Don't forget
to make the motor pulley slightly smaller.


Thanks. Converting the compressor to single phase should, hopefully,
be easy. Conceptually it is easy, I just should not screw up the
contactor coil wiring. In the worst case, I would need to make some
adapter plate for the motor, but I have some barstock for that, taps
etc. I will check it tonight.

Why should I reduce the pulley diameter of both motors are 2 HP rated?

Thank you!

i


Ignoramus6689 wrote:


I am a sucker for lightly fixing old stuff.

I have a 2 HP 3 phase Speedaire compressor that I bought for resale
purposes.

I also have the following:

1) all stuff for making an RPC with a 7.5 HP idler (cost about $33)

OR

2) A single phase 2 HP motor that I bought today for $10.

So, I can repower my compressor in two ways:

A) Keep it 3 phase and build an RPC for it, sans enclosure. Sell it as
"2 HP Speedaire compressor with 7.5HP phase converter". Sell 2 HP
single phase motor separately.

B) Repower it with a 2 HP single phase motor and sell as "2HP single
phase speedaire compressor". Throw away the 2 HP 3 phase motor.

Both A and B will likely take me about an hour, unless I have to make
adapter plates.

The question is, which route will bring me more $$$.

i