I hope to bring and old Rockwell lathe back to life this weekend.
The lathe is a Rockwell Delta 46-450 1HP 3phase monster with the Reeves
speed control on it.
I would really like to restore this lathe, but I want to see it run before I
spend to much time or money on it.
After some research (love that OWWM) I decided to try the VFD route instead
of replacing the motor.
I got a used Toshiba VFD on ebay for $80.00 and a great manual with wiring
diagrams. I have read that the reeves gear on that lathe works pretty well,
so I may only use the vfd as an inverter, but I really am intrested in the
I also learned that the larger Jet, Delta, Performax lathes use the VFDs
with 3 phase motors. My father has the JET 1642 and I noticed that it also
has a brake resistor. Would this be a good thing to get before I try the
VFD, or is it all that necessary?
I saw a "Hint" in the manual that you might want to set the Maximum
Frequency for an older non VFD designed "General Purpose" motor to max out
at 80hz. Has anyone done this?
To start out, I plan on using the 0-60hz and control the vfd from its own
control panel, how ever, i would like eventually use a remote potentiometer
and run stop switch.
If any one has any additional tips I would appreciate it.
If everything goes ok I will have a great heavy lathe,
If not....I have to get rid of a heavy lathe.....
Have a good day
Rick Cox (in PgHjf.3443$Y% email@example.com) said:
| I hope to bring and old Rockwell lathe back to life this weekend.
| The lathe is a Rockwell Delta 46-450 1HP 3phase monster with the
| Reeves speed control on it.
| I would really like to restore this lathe, but I want to see it run
| before I spend to much time or money on it.
| After some research (love that OWWM) I decided to try the VFD route
| instead of replacing the motor.
| I got a used Toshiba VFD on ebay for $80.00 and a great manual with
| wiring diagrams. I have read that the reeves gear on that lathe
| works pretty well, so I may only use the vfd as an inverter, but I
| really am intrested in the flexibility.
| I also learned that the larger Jet, Delta, Performax lathes use the
| VFDs with 3 phase motors. My father has the JET 1642 and I noticed
| that it also has a brake resistor. Would this be a good thing to
| get before I try the VFD, or is it all that necessary?
| I saw a "Hint" in the manual that you might want to set the Maximum
| Frequency for an older non VFD designed "General Purpose" motor to
| max out at 80hz. Has anyone done this?
| To start out, I plan on using the 0-60hz and control the vfd from
| its own control panel, how ever, i would like eventually use a
| remote potentiometer and run stop switch.
| If any one has any additional tips I would appreciate it.
| If everything goes ok I will have a great heavy lathe,
| If not....I have to get rid of a heavy lathe.....
I don't have any experience with Toshiba VFDs and I'm not a turner;
but I use a Delta (Taiwanese Electronics outfit, not associated with
B&D) VFD-B to provide 3-phase power (from a single phase circuit) and
speed control for a 5 HP Colombo spindle in a CNC router.
I wouldn't hesitate to use the VFD as a power converter or speed
control. My VFD-B is keyboard programmable and one of the groups of
options deals with to stop the spindle. I can either allow it to coast
to a stop or I can provide ramping parameters for a braked stop (right
now I have it set up to do a braked stop so I can do faster tool
changes). Unless you're doing production turning and want to change
workpieces quickly, I don't think braking really makes much sense for
a lathe but YMMV.
The finess of control with a VFD is awesome! I can set my spindle to
run at any speed up to 24K RPM in increments of 0.1 RPM - incredible
overkill since I'd be well-satisfied with 100RPM increments. If the
Toshiba is even "just decent", I'm sure you'll get a lot of mileage
(and enjoyment) from your $80!
DeSoto, Iowa USA
I know that you don't want to exceed the nameplate frequency on the motor
unless it is specifically rated for use with a VFD. Not all 3 phase motors
are. If 60 hz gives you an adequate speed from the motor, I would set the
max to 60. There is no need to set it higher than you will be using it.
Try to figure out what the inrush of the drive itself is on powerup. Some
drives have a very high inrush current and you may need a larger circuit
breaker and wiring to supply it than you think. This effect is more
prevalent if you power the drive with residential, 'dual phase' power rather
than 3 phase power.
Would the "Inrush" be listed in a typical Manual.
The VFD I have is a Toshiba model vfs7s 2007up. It was manufactured in '97.
It is rated at 4.0 amps at 1.6kva 0.5-80hz.
Thanks for the heads up.
The ability of this drive to run your fully loaded 1HP motor may
depend on the internal circuit design. A 220V, three-phase, 1HP motor
draws about 3.5 to 4 Amperes at full load. Although some drives have
rated short-time overload capability, the above rating doesn't allow
much headroom for overload. You didn't state the voltage rating of
the drive, but I'm guessing it has capability to 480V (or possibly
600V). That would make the 1.6kVA rating more plausible for its 4A
current rating. No matter what the kVA rating is - AMPS are AMPS, and
that will be the limitation for power output capability of the drive.
But, there's another issue here - using a VFD to convert single-phase
to three phase may also require some internal control circuit
modifications. Most three-phase VF drives still require three-phase
input to work properly AS DESIGNED. Since an AC drive uses an up
front rectifier section, it could be modified to use single-phase
input. But, the safe current load limit may be reduced, depending
upon the current rating of the rectifier power units (assuming you can
use a single input phase of the rectifier). Since the current rating
of your drive is already marginal for a 1HP, 220V motor at full load,
you might not get fully rated performance from your 1HP motor without
overloading the drive. (Discussion assumes the 'modification' is
already feasible - which may not be true.)
Most variable speed drives aren't typically used to convert
single-phase input to multi-phase output. Custom design may be
Just a few things to ponder,
I've seen some good info and some misinformation in the thread. I don't
know the Toshiba model numbers well enough to know if this is native
single phase or not. I think I have a VFS7 manual pdf at work. If it is
it will say it on a tag on the side of the drive and list something
like input 8A 1 phase. If it only lists 3 phase on the tag, you probly
have to derate it. If it has a 1 phase rating, the manual will state it
somewhere. (If you can find the toshiba drives website (tic something,
but a bit hard to track down, look for legacy drive), they have
downloads you can search for the word single.
If you have to derate, you get about 60% of the 4.0 Amps, or 2.4A
continuous. It will start your motor by itself, probably start the
motor and Reeves drive, and may even power the lathe for continuous
moderate cuts. It will put out 2.4 X 150% =3.6A for a minute at a time,
which will cover the full 1hp for any 1hp 1750 rpm motor I've seen. A
bit wimpy for you lathe, but probly passable. If you don't have to
derate, its fine. I don't remember any Toshiba's having undefeatable
input phase loss detection, though they might. If a drive does have
phase loss detection, and you can't defeat it, then it will not run on
single phase. Often manuals don't say whether you can run single phase,
but you can anyways.
Toshiba is one of the few manufacturers to include recommendations to
overspeed your motor; in an earlier VFD manual (VFSX) they mention for
a 1750 motor it is okay to double the speed. 80hz is conservative. If
your motor is a standard frame (56 or 143T/145T), then its easy to
replace, abuse it as you like, a 3 phase replacement is not too pricy.
The comment about the lathe not liking doubling the Reeves high speed
is accurate, but if you don't exceed the lathe's top speed you're okay
at 80, 90, or 100, or even 120 hz, though 80 is "safest". To access
anything over 60, you probably need the remote pot.
If it was made in 1997, then it may have sat around for a while, and
the capacitors need reforming. The best way is with a 240 volt Variac.
slowly ramp up the voltage, then keep it at 240V for 3-4 hours before
hooking a motor to it. Equal is 120 variac + transformer. I think
Variac w/o transformer to 120V,hold a bit, then switch to 240V is next
best. Simply plugging it in for 4 hours at 240V will still do plenty
good. If you don't do this, and it has sat around, it may die quickly
on you. This might be in your manual.
Its only a 1 hp drive, don't worry about the circuit and inrush. The
basic idea is to cover the listed input single phase amps + a safety
factor. But still an easier load on the circuit breaker than a motor
with the same amps, where you have to oversize by more. It will stop
your lathe pretty quickly, I'd try 3-4 seconds min or you start losing
faceplates. You can add a braking resistor if you want LOTS of quick
stops close together. Some you have to add a module for, $$$, justa
resistor, then not bad, though you gotta house it. If you frequently
overheat the drive into a trip from breaking, then get a resistor.
Rick Cox wrote:
I do not exactly know what a variac is, but
I appreciate the advice on hooking it up for a few hours before I hook it up
to the motor.
I have a photo of the tag, and a small pdf of the Vfd manual that I pulled
off the Internet.
I will Post it in my Lathe project Post in
Alt. binaries.pictures.woodworking if you want to see it.
I really appreciate the advice.
First question: What is the service factor of the motor (labelled SF
on the label)? If you have a 1HP motor with a SF of 1.3, you in
reality have a motor that can run at 1.3 HP for a short time. If your
VFD has only enough oomph to run a 1.0HP motor (the real oomph of the
VFD is expressed in Amps, not in HP), then the VFD will be overloaded.
Which is OK - most VFDs handle overload very gracefully, and have
internal safety circuit that will shut down cleanly. In a tool, this
is easy to deal with, because you can control the load by controlling
feed pressure etc.
We had a 1HP water pump converted from single phase to 3 phase. The
pump shop insisted that they have to put a 1.5HP motor on, because the
old single-phase motor had a service factor of 1.35, and a 1HP 3-phase
motor with a serivec factor of 1.0 would not be able to spin the pump
at full speed, and would overload. It then turned out that a 1HP VFD
was marginally able to power the 1.5HP motor, but only at a line
voltage of 240V (at which voltage the motor uses fewer amps); when
running on the emergency generator, at a line voltage of 220V, the
motor draws a few more amps, and the VFD went into overload shutdown.
I replaced the VFD with a 2HP model, and everything runs excellent.
Warning: not all VFDs are able to run on a single-phase input, but
some are. Look at the spec or manual for it. Some VFDs absolutely
require a 3-phase input.
Read the manual for the VFD. The brake resistor is needed if you
program the VFD for rapid braking - the energy stored in the motor and
in the mechanically moving parts has to be dumped somewhere. If you
program your VFD for coasting to a stop, or for a very gentle rampdown
without braking, the resistor will not be needed. You might want
ultra-rapid braking for an emergency stop, though.
It's not just about the motor. If you have a system that's designed
for 3600 RPM at 60Hz, and you run it at 80Hz, everything will spin at
4800 RPM. There may be parts of the drive that don't survive this
(whether immediately or long-term is an interesting question). Also,
to spin all that stuff at a much higher RPM might require much more
power from the motor, and you might overload it and fry it. If you
forget to program your VFD to honor the maximum current from the motor
nameplate, you might burn out the motor.
Another warning: Some old motors don't like running at low frequencies
either. For a motor to deliver high torque at low RPM on a VFD, it
has to be built quite differently: more cooling, better voltage
insulation in the coils to handle the foltage spikes from the
high-frequency drive of the VFD, and so on. It seems to be pretty
safe to take any old 3-phase motor, and run it at 60Hz, maybe with a
few seconds of rampup and rampdown. Whether it is afe to a run an
older (non-VFD-rated) motor at underfrequency is a topic of a lot of
One HUGE advantage of 3-phase motors on VFDs: you can program the VFD
to ramp the motor up and down slowly (over a 5-second period). This
gets rid both of the electrical startup surge of the motor, and all
the mechanical stress of the motor jerking on or off.
Run/stop switch is easy, as most VFDs have inputs for those. I would
go with a mushroom-style emergency off. Note that by using a VFD, you
also get the functionality of a magnetic starter: You can program the
VFD to not restart after a power interruption.
A remote potentiometer is a little harder, as the good ones (with big
dials) are hard to find, and not all VFDs have an analog input. I
want to do the same thing to my drill press: I'll replace the existing
single-phase motor with a 3-phase motor, and replace all the control
Last warning: The high-frequency output of a VFD is considerably more
dangerous (in the sense of electrical shock) than regular 60Hz. Make
sure the frame of the motor is really well grounded. Being the
paranoid type of person myself, I install VFDs in metal enclosures,
and use non-flexible metal conduit to connect the VFD enclosure to the
motor itself, making sure everything is really well grounded. Better
safe than sorry (or dead).
Unless you really screw up, you will at least have a heavy lathe with
a fixed-speed motor, and gentle rampup/rampdown.
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