Motor horsepower?

T

Timy

Well-Known Member
So what do I gain from upgrading my motor from 1hp to 2hp?

Same speed obviously with the rpm at 1725 correct?

Logic says you increase the hp you increase the power ala motors in cars and motorcycles etc

but does that mean, more torque, or the ability to grind thicker steel without bogging it down or blowing the breaker?

Would love an explanation on this.

Thanks guys.
 
Yep, that means more torque, the ability to grind thicker steel without bogging it down, but has no affect on blowing the breaker. The breaker will need to be rated to carry full amps for the 2hp motor rather than just 1 hp. A 2hp motor "normally" will run on 240vac while a 1 hp is easy to power on 120 VAC. Understand, a 2 hp motor doesn't really know the difference in 120 vs 240 VAC "IF" there is no voltage drop. The problem is 2 hp will require twice the current on 120VAC as will the 1 hp. Typically to start a 1hp will require about 14 amps (20 amp breaker is good) on 120vac while only 7 amps (a 15 amp double pole breaker would be good) on 240 VAC single phase.

The actual running amps will be less, but when hogging, you will come real close to those amps.

Ken H>
 
Timy, instead of 2hp I would make the leap to 3hp. Even though a 2hp is better than a 1hp it still isn't saying much. Last weekend I made the switch form 2hp to 3. I can still stop it, but I have to really try. During normal blade grinding it doesn't slow down one bit.
Just something to think about if you are planning a jump.
 
Timy said:
So what do I gain from upgrading my motor from 1hp to 2hp?

Same speed obviously with the rpm at 1725 correct?

Logic says you increase the hp you increase the power ala motors in cars and motorcycles etc

but does that mean, more torque, or the ability to grind thicker steel without bogging it down or blowing the breaker?

Would love an explanation on this.

Thanks guys.
Click to expand...

If you going to be buying a vfd then I too would recommend a 3 hp motor. It seems like they can be had for the same or sometimes less money. So why not? This would require a vfd that could handle it. This also means 220v input. The 2 hp motor will output 1.5 hp if used with a vfd.

What are you thoughts on going variable speed? If yes then 3 phase motor and vfd are needed. Buy it once and you'll not need to upgrade in the future and the vfd will be able to control lesser hp 3 phase motors as well.
 
Already ordered a 2hp. Should be perfect for my small to medium knives. I rarely go above 1/8, staying mainly with 3/32 but nice to be able to push, I mean I did make 50+ knives using the 1hp so 2hp is gonna be a big upgrade.

I like the idea of a vfd, but really dont mind the 3 step pulley. Vfd is just out of my price range right now. Even if it was, I would probably just buy more supplies.

Thank you for all the help though guys.
 
Timy, I think you'll be just fine. I've got a 2 hp, 3450 RPM single phase motor on my grinder. I use a 4 step pulley and only a 3" drive wheel on belt to keep belt speed slower - still tops at 5K FPM which is faster than I'll grind. With belt in 3rd pulley giving about 3800 FPM I have a VERY hard time bogging motor with an 8" contact wheel - and this is with 1/2" steel plate. On 1/8 to 3/32" knife blade, not sure I could bog motor. If you've got a 4" drive wheel, your top speed should be around 3600 FPM and that will hog some metal! Slipping the belt to low speed will give you a nice slow 900 FPM for "touch up" work. (edit) assuming you have the usual 2/3/4" 3 step pulley.

You do have your motor mounted on a hinged base with weight of motor provide any belt tension? This allows a very quick 'n easy belt speed change.

PT Doc - why does a 3 ph 2 hp motor only provide 1-1/2 HP on a VFD at 100% speed?

A valid reason for a 3hp motor using a VFD would be to have more power at reduced speed. By reducing the speed (freq of drive) the motor does have less power - the slower you go, the less power. While with a step pulley, the slower you go, the more power you have<:)

Ken H>
 
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