06-28-2012, 12:53 PM
Hi Andy,
Hoover made quite decent motors, way back then...
From the motor plate it seems it's star wound and (can't see for sure) 415 - 440V, so *if* you can get inside and find the star point, you can convert it to 240V 3-phase and use a cheap VFD by bringing the windings out and wiring it in delta - That'd be my choice, a VFD's slight overkill on a shaper, but the soft-start etc. are well worth having! If you're really lucky, there'll be a set of six terminals where the 3-phase comes in with one each for the phases, the other 3 linked - if so, swing the links so they go "across pairs" instead of down one side and it'll be in delta connection. A VFD putting out 750W / 0.75KVA will be plenty for a 3/4 HP motor. A 415V VFD can be run from 240V too, but you need to "derate" it by 30 to 50% if you're going to do it?
Re the 950 RPM, that'll be because it's a 6-pole motor (as opposed to the usual 2 or 4) - "pole switching" on motors can give a range of speeds, my lathe uses a 4 - 6 - 8 pole motor for 1440, 950 and 720 RPM, although only the 4 - 8 pole is done with a single winding (tapped in the middle), the 6-pole's a separate winding, this is probably why it needs 9 wires into the switchgear and is almost dustbin-sized! It does make the full 3 HP in each speed, though... And with a 5HP VFD on it providing 415V from 240V single-phase it gives quite a wide speed range :) The "hack" to get a 415V VFD to run from 240V is pretty simple, easier on older, cheaper and *bulkier* VFDs from Ebay!
Just my ha'pennorth,
Dave H. (the other one)
Hoover made quite decent motors, way back then...
From the motor plate it seems it's star wound and (can't see for sure) 415 - 440V, so *if* you can get inside and find the star point, you can convert it to 240V 3-phase and use a cheap VFD by bringing the windings out and wiring it in delta - That'd be my choice, a VFD's slight overkill on a shaper, but the soft-start etc. are well worth having! If you're really lucky, there'll be a set of six terminals where the 3-phase comes in with one each for the phases, the other 3 linked - if so, swing the links so they go "across pairs" instead of down one side and it'll be in delta connection. A VFD putting out 750W / 0.75KVA will be plenty for a 3/4 HP motor. A 415V VFD can be run from 240V too, but you need to "derate" it by 30 to 50% if you're going to do it?
Re the 950 RPM, that'll be because it's a 6-pole motor (as opposed to the usual 2 or 4) - "pole switching" on motors can give a range of speeds, my lathe uses a 4 - 6 - 8 pole motor for 1440, 950 and 720 RPM, although only the 4 - 8 pole is done with a single winding (tapped in the middle), the 6-pole's a separate winding, this is probably why it needs 9 wires into the switchgear and is almost dustbin-sized! It does make the full 3 HP in each speed, though... And with a 5HP VFD on it providing 415V from 240V single-phase it gives quite a wide speed range :) The "hack" to get a 415V VFD to run from 240V is pretty simple, easier on older, cheaper and *bulkier* VFDs from Ebay!
Just my ha'pennorth,
Dave H. (the other one)
Rules are for the obedience of fools, and the guidance of wise men...
(Douglas Bader)
(Douglas Bader)