static or rotary converter for grinder

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bosephus

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i bought a 5 hp 3 phase baldor grinder on Craigs list for a whopping $25 .
i have a 10 hp motor to build the rotary converter with , and everything i need to build a static converter as well.

whats the best option for a grinder ,.. while i do understand how to build a converter i know very little about electrical in general , my first instinct is to just build a rotary converter as then i can power anything else i might happen to pick up in the future .

but then again .. i do not have any other three phase machines and not having to start a converter every time i want to use the grinder is attractive as well
 
Go rotary. RPC or VFD- your motors will appreciate it.

Randy
 
Hi Steve,
Dependent on how intricate you'd like to get, you could have the RPC start and stop by the controls of the grinder, if you were worried about the RPC running for only the grinder at this point.
adaptations can be made to to the generated 3 phase circuit later on for additional machinery.
 
i like to keep things simple , i get easily confused when it comes to wiring .

either of two is with in my comfort zone to do , but getting fancy with it ... well lets keep in mind i am fairly ignorant of electical once things go beyond a simple on and off switch
 
bosephus said:
i bought a 5 hp 3 phase baldor grinder on Craigs list for a whopping $25 .
i have a 10 hp motor to build the rotary converter with , and everything i need to build a static converter as well.

whats the best option for a grinder ,.. while i do understand how to build a converter i know very little about electrical in general , my first instinct is to just build a rotary converter as then i can power anything else i might happen to pick up in the future .

but then again .. i do not have any other three phase machines and not having to start a converter every time i want to use the grinder is attractive as well
Click to expand...


Congrats on the find!

I have a 3 HP 2X71 grinder and I first ran it with a rotary converter and have since installed a VFD. They both work, but the VFD of course, can slow the motor down with the twist of a knob... which I find quite handy.


FWIW I just bought a cheap chicom water mister, if you do a lot of heavy grinding its supposed to help. Haven't tried it as yet.

paul
 
Build yourself a 10 hp rotary converter. Then you're all set for the next deal too. plenty of guys here to help you "cookbook it" so its simple to do. I made a couple of mine just run when you flip on the circuit breaker - VERY simple wiring.

Or sell me the grinder and save all the pain and heartache of getting hooked on this hobby :roflmao:
 
aah its always nice to know theres plenty of people out there willing to take a headache off your hands , lol


this morning i figured my first best step was to make sure the grinder actualy works , so i spent some time and wired my 10 hp motor up and grinder , and with the flip of a switch and a pull on a rope to start the idle motor it came alive .

so now after lunch comes the hard part for me,.. making my converter self start . ok so thats not the hard part for me , what i am only about 25% sure of is wiring in the magnetic switch/relay thingamabob so i dont have to worry about the converter coming back on after a power outage ( very common in the winter months in my rural area ) if i forget to switch it off .

i think i am going to have a a slew of wiring questions in the near future ... it apears that i may have a two speed motor , and i dont have a clue how to make it two speeds again .

in another bit oh honesty ,.. no i did not check the grinder out in the slightest when i bought it , i showed up handed the fella his $25 and wrestled it into my nephews pickup truck ,.. i just didnt care , the cast iron base alone was worth a lot more to me then the measly $25
 
I'd take that 10hp motor and make an RPC out of it. Like others have said, then you'll have 3ph power for whatever comes down the pike. You'll save a lot of money too, since you already have the motor. There are quite a few threads here on making an rpc with capacitors to have it self starting etc.
 
bosephus said:
i bought a 5 hp 3 phase baldor grinder on Craigs list for a whopping $25 .
i have a 10 hp motor to build the rotary converter with , and everything i need to build a static converter as well.

whats the best option for a grinder ,.. while i do understand how to build a converter i know very little about electrical in general , my first instinct is to just build a rotary converter as then i can power anything else i might happen to pick up in the future .

but then again .. i do not have any other three phase machines and not having to start a converter every time i want to use the grinder is attractive as well
Click to expand...
since you already have a 10hp motor i would build a rpc . the static converters will cut your available power. i use a rpc in my shop and have a 3ph circut wired thru the shop to use with other machines. it works great. thats a mighty big grinder.probably uses 12 inch wheels? very expensive. rpc's are very nice and have a lot of programable features, but you pretty much need one for every machine to take full advantage of all the functions. if i were starting from scratch and didn't have access to a free motor i would certainly consider that route.
 
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