1725 or 3450 rpm????

[rbertalotto]

Thank You...Mill does not have a back gear. I ordered a 1725 rpm motor....

 

[verbotenwhisky]

Since you folks answered my last question so quickly about a VFD being either 120v or 230v input....Here's another question.

The milling machine currently has a 1.5hp / single phase /1725 rpm motor

Is there any advantage to replace it with a 3450 rpm motor....

Is there any power loss with a VFD and should I up the HP to 2hp or maybe even 3hp?

Thanks again....

Opinions are like________ everyone has at least 1 and mine is, I would maintain the same RPM, if you would like more power, go for more HP at same RPM... I have turned stuff at high enough RPM, in the past, to exceed sonic velocity at the outer edges of circular parts which is generally where things come apart and accelerate to places unknown, I am alive by the grace of God only.

If I were going to double the speed +/- 50 RPM I would do some calculations concerning all the rotating parts to insure every thing is okay.

 

[lesorubcheek]

In my other life in the glass industry. We found it was better to over speed a motor instead of running it below rated speed. I talked to several motor/VFD suppliers and they all agreed. An 1800 rpm motor has no problem runnung at 3600 rpm. We used MANY 1 to 3 hp 460 volt motors on our inspection lines and equipment. The VFD's replaced the original DC drives that had a high failure rate for various reasons. We operated 24/7/365 and bean counters didn't like to stop and fix things.

Thanks for this information. We were just discussing this question. Investigating a 3 phase 1hp motor for use on a lathe (which we don't have yet!). The motor needed will likely need to be 1725 rpm. Found some inexpensive 3450 rpm motors also rated at 1hp. So, it'd be easy enough to run one of these at half speed using a vfd, but somehow it just doesn't seem it would provide the same power. I've never looked into variable speed electric motor torque curves, but would guess they're not a constant at any rpm. Since HP is torque x rpms, it brings up the question of how these motors are rated and what their actual power is at different rpms.
Dan

 

[verbotenwhisky]

Thanks for this information. We were just discussing this question. Investigating a 3 phase 1hp motor for use on a lathe (which we don't have yet!). The motor needed will likely need to be 1725 rpm. Found some inexpensive 3450 rpm motors also rated at 1hp. So, it'd be easy enough to run one of these at half speed using a vfd, but somehow it just doesn't seem it would provide the same power. I've never looked into variable speed electric motor torque curves, but would guess they're not a constant at any rpm. Since HP is torque x rpms, it brings up the question of how these motors are rated and what their actual power is at different rpms.
Dan

My Mill has a 2HP 3Ph motor on a VFD, I will look and see what the RPM is on it, It will run a 3" face mill through a chunk of aluminum .300 deep with out bogging down at all.