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Mark Main
 
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Default VFD used with either a 3~ Rotary Converter or Phase Inverter

I'm a newbie who's trying hard to do my research before simply
asking the dumb newbie questions; despite my efforts I still need to
helpful coaching.

Here are my 3 key goals:
1. Using a 5 or 10HP 3~ motor, I want to control the full 40-4000 RPM
range of a Monarch 10EE directly from the machine, without swapping
belts, and with minimal torque loss/variance; and possibly increase the
RPM to 4500 or 5000.
2. I want to convert/provide 3~ power throughout my shop from my
standard 1~ grid power.
3. I want to be able to run 1 or more 3~ machines at a time up to a
combined maximum of 10 or 15 HP, and to control their RPM speed
directly on each machine.

STEP 1: SAFELY/CONVENENTLY PROVIDE 3~ SHOP POWER

The two best shop options seem to be a Rotary Converter or Phase
Inverter.

ROTARY CONVERTER
If I build one myself here is what sounds like the best recommendations
I've read (please let me know if you disagree or have any other
suggestions):

1. Size the idle motor 1.5x my maximum HP needed (e.g. 15HP x 1.5 =
22.5 HP+).
2. Automatically power the converter with the shop lights or with a
sensor detecting that power is desired by a machine. Power should be
turned off automatically with a drop in grid power, when the shop
lights are turned off, and possibly after a certain delay from non-use
(e.g. 30-minutes).
3. Automatically self-start the idle motor by compromising (staggering)
the capacities of the tuning capacitors during the startup process, and
then once running, relays can engage additional capacitors to restore
balanced capacitor capacity ("tuning") between the 3 phases, in
order to optimize the balance of voltage/current in the generated phase
to match the other two phases. BTW, I really would like to learn more
about this in greater detail.
4. After the tuning has taken place, I've read that you can also add
a power-factor correction capacitor across the line power leads coming
into the converter to minimize any out-of-phase current flow into the
idler motor. This apparently should not affect your home electricity
costs, but will probably affect commercial rates. Also, it is important
to note that this can trip circuit breakers if you become close to the
maximum rating. I would like to learn more about this from 'DoN.
Nichols' (who first wrote about it) or others if possible.

PHASE INVERTER

I've not read much about this other than I know that a modified sine
wave is more accurate, but it I don't know if that really matters to
a motor. Are phase inverters more expensive than building your own
rotary converter? What are some good sources?

STEP 2: SAFELY/CONVENENTLY VARY MACHINE SPEED WITHOUT TORQUE LOSS

It sounds like the preferred option, using the latest technology
available today, seems to be VFD (variable frequency drives). Most
people use a single VFD to control power for the entire shop and locate
this near (or on) the machine that would most benefit from having
variable speed control nearby.

If I want to have this convenience on every machine then it appears I
will need to purchase a VFD for each machine rate at the power for that
particular machine.

Am I wrong with my understanding? Is there a better way to adjust the
RPM for the full range of the Monarch 10EE without severe torque
impact?

Can I modify a 4000 RPM rated machine to run a 4500 or 5000 RPM?

What are great sources for new or used VFD's?

Thanks to all in advance for your help.