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4x60 belt grinder build.


Jeremy Blohm

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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. 

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  • 1 month later...

"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. 

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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 by Jeremy Blohm
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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.

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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.

 

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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.

-Brian

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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.

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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.Resized_20190426_212330.jpegResized_20190426_212357.jpeg

here is everything on the stand it will be mounted on.Resized_20190427_105313.jpeg

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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.:unsure:

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

Edited by Jeremy Blohm
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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?

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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! Sander.jpg

 

C Craft Customs ~~~ With every custom knife I build I try to accomplish three things. I want that knife to look so good you just have to pick it up, feel so good in your hand you can't wait to try it, and once you use it, you never want to put it down ! If I capture those three factors in each knife I build, I am assured the knife will become a piece that is used and treasured by its owner! ~~~ C Craft

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

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

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  • 2 months later...
On 4/26/2019 at 10:47 PM, Jeremy Blohm said:

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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.

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Edited by Jeremy Blohm
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