RPC or VFD for 5hp Planer? 15hp RPC too big for panel service?

Hi Guys!

I'm dying to get this 16" planer up and running. It's a 5hp 16" old powermatic planer.

I bought a huywang 5hp rated VFD but I'm not confident it will work. My dad dropped off a 15hp baldor 3 phase motor few weeks ago. Plan is turn that into a rotary phase converter.

The more I research, the more questions and I have.

#1 - I have a 100amp single phase service panel. Is this enough to run the 15hp baldor 3 phase motor? The motor is missing the nameplate, I have no clue on stats aside from it being an old, likely 30 year old, 15hp 3 phase motor.

#2 What is the likely amp draw of the 15hp motor when on AND the planer being used?

I'd prefer the RPC route because in the wiring process, we'd add a couple 220v plugs and breaker box to plug other 3 phase machines into.

#3 Is wiring the VFD easy to do? The directions and posts online make it sound tough cuz the manual is terrible. If wiring the VFD, I'd like to put a male plug on in and plug it in when ready to use the planer and unplug it when I need the outlet for other tools.

I thought about finding a 5hp single phase motor but they are $$$ and the mount and shaft size have to match and it also messes with the original switch.

Your panel should handle the 15 hp load. Use a 80 amp breaker. I also have a 16 inch Powermatic planer with a 5 hp motor. I used a 7.5 hp converter until I switched over to single phase. Try to find a smaller motor for your converter. Bob

Bob-J-H said:

Your panel should handle the 15 hp load. Use a 80 amp breaker. I also have a 16 inch Powermatic planer with a 5 hp motor. I used a 7.5 hp converter until I switched over to single phase. Try to find a smaller motor for your converter. Bob

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Hi Bob, thanks for the reply.

I'm also debating just switching to a single phase motor. I can't find, without paying a lot, a 5hp single phase with a 184t mounting plate @ 3450rpm. I see a lot of 7.5hp single phase @ 3450rpm. It's about $350 shipped. I'll have to measure my input shaft and see if they works. Would going with a 1700rpm motor and changing pulleys be a total pain?

I'll also look for a 10hp 3 phase motor for the RPC. I'd feel much safer using a 10hp than the 15hp especially mine without nameplate.

I use a 1750 rpm motor on my planer. Just a matter of changing the pulley and probably the belts. Bob

I run a 15 hp converter on a 100 amp panel using a 70 amp breaker.This unit has powered a 10 hp air compressor that starts hard and a 7.5 hp table saw. Have had no issues since built over 30 years ago.The converter is a self start unit.My supply transformer is a 25 kva unit on my farm.

No reason not to use the VFD if you have it, but you would want to run the planar from the VFD panel not the machine power switch. Not that difficult to program to get it to run.You can also easily wire up a low voltage run/stop switch. If dedicated to the planar, just put a plug on the VFD and unplug it when you do not need it.
OR get a replacement single phase motor, something like a Baldor
184T frame 1.125" shaft, if you need a motor pulley they run about $25.
L1430T 1725 RPM will run about $350 shipped
L1409T 3450 RPM will run about $450 shipped

Psychbiker said:

Hi Bob, thanks for the reply.

I'm also debating just switching to a single phase motor. I can't find, without paying a lot, a 5hp single phase with a 184t mounting plate @ 3450rpm. I see a lot of 7.5hp single phase @ 3450rpm. It's about $350 shipped. I'll have to measure my input shaft and see if they works. Would going with a 1700rpm motor and changing pulleys be a total pain?

I'll also look for a 10hp 3 phase motor for the RPC. I'd feel much safer using a 10hp than the 15hp especially mine without nameplate.

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I know nada about the Powermatic, but as to single-phase... early 1970's 'we' sawed the CI housing half-way off a "vintage' (1940's?) and rather stout Newman 600 planer of similar size. It had, IIRC, a built-in 3-P motor, common-shaft with the cutter-head, and of about six HP.

The owner had serious volume & discount status with W.W. Grainger, so a Dayton "farm duty" 5 HP single-phase, and three-row Morse CI pulleys, QD hubbed, to run "B" section belts were grafted on.

A recycled Chevie pickup shock absorber and some stock coil springs kept the welded-up swing-table on good behaviour. Crude, but effective, and rough-sawn local hardwoods were made a meal of to good effect.

Ergo, I'd personally go RPC only if it is cheaper and easier than single-phase, and VFD not at all.

2CW

Planning to tackle this VFD tomorrow and monday.

Regarding wire, would 12/4 600v SOOW from home depot work on both ends? From the single phase in to the VFD and then VFD to motor? I've read some will run a small section of conduit on the motor to VFD side. My dad dropped off 10awg solid copper and I know that won't work.

A 5 Hp VFD usually specifies 10AWG as a minimum and some specify 8AWG for single phase input, you only need 10/3 no neutral. On the output to the motor 12/4 600V would be OK, but usually they also specify 10AWG. Some VFDs can often put out 150-200% of their rated current for up to 1 minute, so on a longer run I would use 10AWG. The issue you will have with your VFD is the terminals are tiny for the rated current, something like a M4 screw size and they take very small spades/ring terminals if used. I would not use solid core wire. You can run some 3/4" PVC or metal flexible conduit and pull stranded wire going to the VFD or just use 10/3 SOOW to the the VFD. Going to the motor I usually use shielded VFD cable or run stranded wire in flexible shielded liquid tight conduit for longer runs, but plain 10/4 or 12/4 to the motor will also work for short runs.

mksj said:

A 5 Hp VFD usually specifies 10AWG as a minimum and some specify 8AWG for single phase input, you only need 10/3 no neutral. On the output to the motor 12/4 600V would be OK, but usually they also specify 10AWG. Some VFDs can often put out 150-200% of their rated current for up to 1 minute, so on a longer run I would use 10AWG. The issue you will have with your VFD is the terminals are tiny for the rated current, something like a M4 screw size and they take very small spades/ring terminals if used. I would not use solid core wire. You can run some 3/4" PVC or metal flexible conduit and pull stranded wire going to the VFD or just use 10/3 SOOW to the the VFD. Going to the motor I usually use shielded VFD cable or run stranded wire in flexible shielded liquid tight conduit for longer runs, but plain 10/4 or 12/4 to the motor will also work for short runs.

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Why 10 gauge? 12 is rated for 20 amps right? My 5hp 3 phase says 12.5 amps on the name plate.

I've been researching this for sooooo long and not making any progress.

I brought home a big bundle of 12/3 wire and an additional 12awg for the motor side ground. Then read how 10awg may be needed.

Does the VFD draw more amps than 12.5 or less than 12.5 if my 5hp 3 phase motor says 12.5 amps on the name plate?

12.5 x 1.732 = 21 amps. That's if the math is correct.

Psychbiker said:

if my 5hp 3 phase motor says 12.5 amps on the name plate?

12.5 x 1.732 = 21 amps. That's if the math is correct.

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yes, that is correct but that is for unity power factor. figure .5 to .6 power factor for single phase into a rectifier.


you could have 40 RMS amps going into the vfd for a 5 hp motor (but only at full load), but your utility watt meter will only bill you for 21 amps, as you calculated.

johansen said:

yes, that is correct but that is for unity power factor. figure .5 to .6 power factor for single phase into a rectifier.


you could have 40 RMS amps going into the vfd for a 5 hp motor (but only at full load), but your utility watt meter will only bill you for 21 amps, as you calculated.

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I am completely puzzled at the assertion that a VFD would have a power factor down around 0.5 or 0.6. My understanding has always been that the full wave rectifier and capacitor bank within the VFD, combined with the isolation through the switching stages, isolate the motor's power factor from the grid-based supply, and that the VFD shows the grid something fairly close to unity power factor:
Improving Power Factor with Variable Speed AC Drives | Electrical Construction & Maintenance (EC&M) Magazine I can't see why a single phase input VFD would be particularly worse, as either way the conversion to DC is complete; it just draws more current over one phase than a 3-ph VFD would spread over all three phases.

Oh, and by the way, back to the original topic of the discussion, I am able to start a 7.5hp RPC through a 30 amp breaker fed through a sub-drop from my house to my shop that is only 10awg. My RPC never has more than 3hp on it, it's just the size of RPC for which the parts were pretty much given to me, and it gives me options to run multiple machines at the same time. Someday bigger AWG from house to shop will rise to the top of the project list, but, for now, it works. To my amazement, the 7.5hp VFD doesn't even cause a momentary flicker of my shop's lights when I start it up.

So, since I am able to handle a 7.5hp RPC, partly loaded (3hp) over a 30A circuit, I'd expect that you would be just fine with a 15hp- powering only your 5hp shaper- fed with a 100A service.