Thread: Wanted to buy - second hand 240 volt (5HP or 4 HP) motor

A bit late after your original post, but here goes anyway.
I think you may need to step back from the HP you desire and consider a 3HP.
5HP from 240V is a lot to ask and a 15A outlet will not be up to it. Carbatec sell a 20" thicknesser with either a 5hp 3 Phase unit or a 3Hp 240v. I take this as a hint that 3Hp is the practical maximum for 240v supply.
All the drop in HP means is that your max depth of cut will be less.
Have you considered a phase converter? This would open up a whole range of options if you have/want more gear.

Karl,

Thanks for taking the time to share your wisdom. This is useful information.

Cheers.

Regards,
Ben

To add to my last post.
A rough calculation of the supply requirements would be as follows.

• 1HP = 750 watts
• 4HP = 3000 watts

These are OUTPUT figures so we must then allow for the 70% efficiency of a single phase motor, (3 phase is around 90% by the way), this translates to an input figure of around 4300 watts.

• 4300 watts divided by 240V = 17.92 Amps
• This is normal running @ 4HP startup current will be far greater.

For a 5HP the numbers would be.

• Output 3750 Watts
• Input 5360 Watts
• Current 22.3 Amps

CMG do make a 5HP single phase motor, it's an MT series motor and is a 1500 RPM 4 pole motor.
As an aside the going rate last time I looked was around $10-15/HP for second hand 3 phase motors with single phase being at least 2-3 times more expensive.
You will need to get the specs off your existing motor when you source a single phase so you can match rpm's etc plus your switchgear may need to be changed.
Hope this helps.

Interesting stuff. I have learnt something today.

Originally Posted by Karl Robbers

To add to my last post.
A rough calculation of the supply requirements would be as follows.

• 1HP = 750 watts
• 4HP = 3000 watts

These are OUTPUT figures so we must then allow for the 70% efficiency of a single phase motor, (3 phase is around 90% by the way), this translates to an input figure of around 4300 watts.
[LIST][*]4300 watts divided by 240V = 17.92 Amps[*]This is normal running @ 4HP startup current will be far greater.
.

It's running current will also depends on what load it is under. About the only wood work machine that operates continuously on a full load is a dust extractor freely pulling air. The current drawn by all other machines will depend on the applied load. For example; my 3 HP TS free runs at about 5 A; cross cutting small pieces of pine it will pull maybe 6 A. Depending on how hard it is pushed it only pulls 10A (3HP) when I rip 75 mm thick Jarrah. Ripping 100 mm Jarrah slowly makes it pull about 12 A. If I really try to stuff 100 mm jarra throughout it, it overheats and trips out at ~18A.

Originally Posted by BobL

It's running current will also depends on what load it is under. About the only wood work machine that operates continuously on a full load is a dust extractor freely pulling air. The current drawn by all other machines will depend on the applied load. For example; my 3 HP TS free runs at about 5 A; cross cutting small pieces of pine it will pull maybe 6 A. Depending on how hard it is pushed it only pulls 10A (3HP) when I rip 75 mm thick Jarrah. Ripping 100 mm Jarrah slowly makes it pull about 12 A. If I really try to stuff 100 mm jarra throughout it, it overheats and trips out at ~18A.

Very true, the figures I gave were at rated output. Another point worth mentioning is that single phase motors also have relatively poor torque characteristics when compared to 3 phase.
Allowing for the 70% efficiency, a current draw of 10A equalling 2400 watts will equate to an output of 2.25HP
A 5HP 240V single phase motor is a serious piece of gear, well beyond the realm of most domestic power supplies, not to mention the fact that I would imagine the price would be somewhat heart stopping.

I don't know what these are like but a brand new 5HP, 240volt motor at 2800RPM for $250 seems to be pretty good value.
Chinese made with a years warranty.
I have no idea how many amps this would pull.
This guy also sells the same motor at 1400RPM

Electric motor single-phase 240v 3.7kw 5HP 2800rpm shaft 28mm | eBay

Stewie