4x60 belt grinder build.

[Jeremy Blohm 388]

Time to start another project. I'm probably going to turn it into a surface grinder after I gather up some more things. As for a VFD I'm thinking of putting a 5 hp 3 phase motor on it and using a VFD on it. The reason for the 5 HP is because running a 3 phase motor on a VFD you only get 2/3 the rated HP just like running a static phase converter. 

[Jeremy Blohm 388]

Made some progress.

[timgunn 18]

"The reason for the 5 HP is because running a 3 phase motor on a VFD you only get 2/3 the rated HP just like running a static phase converter."

That's news to me. What is your source for this information?

I'm pretty sure it's wrong generally, though there may be specific circumstances under which it is the case. The only one I can think of offhand is when the supply Voltage is less than the motor rated Voltage, but I'm sure there are others.

I've been using VFDs for over 30 years and I've never been told by a motor- or drive-supplier that I need to derate a motor by 1/3rd in order to run it from a VFD. 

[Jeremy Blohm 388]

Ok so I was wron about the 2/3 hp from a VFD. I have only used a VFD in a factory setting where everything was 3 phase in and 3 phase out. I "assumed" it worked the same way as a static phase converter. I never realized it converted the power to a high voltage DC current and stored it in a dc-type electrolytic capacitor then converted it to true 3 phase power. 

I'm glad you said something and pushed me to do my research.

Edited April 25, 2019 by Jeremy Blohm

[JeffM 66]

not quite sure I am seeing the surface grinder vision in this one

[Jeremy Blohm 388]

It will soon enough. I just need the linear motion rails and the magnetic chuck. I was just bidding on a magnetic chuck but for another $150 on the same auction I could have won an actual surface grinder.

[Jeremy Blohm 388]

16 minutes ago, JeffM said:

not quite sure I am seeing the surface grinder vision in this one

This is what I'm trying for in the surface grinder.

 

[Jeremy Blohm 388]

There is another one similar at 2 min 25 seconds into this video

 

[Brian Dougherty 699]

15 hours ago, Jeremy Blohm said:

Ok so I was wron about the 2/3 hp from a VFD. I have only used a VFD in a factory setting where everything was 3 phase in and 3 phase out. I "assumed" it worked the same way as a static phase converter. I never realized it converted the power to a high voltage DC current and stored it in a dc-type electrolytic capacitor then converted it to true 3 phase power. 

I'm glad you said something and pushed me to do my research.

Yes, you get full rated power out of  a motor using a VFD regardless of your input source assuming that you are providing the input power that is specified y the drive manufacturer.

However, people often don't understand that a motor produces it's rated horsepower at a specific RPM.   Running a 5hp motor at 50% of it's rated speed will result in much less power out even if you are using a VFD.

[Jeremy Blohm 388]

Here it is with the belt under tension and a look at the tensioner and tracking mechanism.

[Jeremy Blohm 388]

This is what the parts came off of. The belt was 4"x101" with a 3/4 hp motor. Needless to say it was way under powered and the belts had to be custom ordered.

[Jeremy Blohm 388]

Here is the motor im going to try to use since the 5 hp will be way to much power. If this is not enough I have a 3 hp 3450 rpm motor I can run it with.

here is everything on the stand it will be mounted on.

[Jeremy Blohm 388]

One thing I didnt look at is if this motor is a TEFC motor. I'm going to have to look at it closer when I get home.

Edit:it says right on the I'd tag it's an open enclosure so im going to use the 3 hp.

Edited April 27, 2019 by Jeremy Blohm

[Brian Dougherty 699]

I'm not sure 5hp would be too much, especially with a 4" wide belt.

[Jeremy Blohm 388]

And with the 5 hp I can run a VFD instead of step pulleys.

[Jeremy Blohm 388]

My 6x48 Kalamazoo is a 3 hp 3450 direct drive connected with a love-joy so I'm definitely going with the 5 hp. You can never have too much power right?

[C Craft 162]

On 4/26/2019 at 9:47 PM, Jeremy Blohm said:

So got to ask Jeremy where did you come up with this piece?? It appears that it was designed specially for that purpose!

 

[Jeremy Blohm 388]

It came off of an old homemade edge sander that was way underpowered.

And you are right it is specially made for this purpose.

[Jeremy Blohm 388]

On 4/26/2019 at 10:47 PM, Jeremy Blohm said:



So I won this belt grinder in an auction for $43. It is 3 phase but ironically it has the same belt tensioner as this one. This is only the 2nd one I've seen like it.

 

Edited July 9, 2019 by Jeremy Blohm