Subject: variable frequency drives

From: [email-masked] (Joe Landau)
Date: Thu, 06 Oct 1994 05:56:57 GMT

An ad in Model Engineer's Workshop magazine (English) offers a gadget from
Mitsubishi that gives: "
* single to three phase operation up to 3 hp
* infinitely variable speed control 
* computer control possible
* more versatile than a "phase converter"
* constant torque output from 3 phase induction motors with lower initial
cost, lower vibration and torque ripple than the single phase alternative.  *
etc., etc. "

The picture in the ad shows a device with a digital display, a few switches,
and the product name FREQROL-U100.  About the size of a standard US wall
switch box. 

I'm unfamiliar with these devices.  Sounds too good to be true, or at least
too good to be cheap.  Anyone know about them?

Joe Landau

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From: [email-masked] (Randy Lee)
Date: Thu, 6 Oct 94 19:04:28 GMT

>too good to be cheap.  Anyone know about them?
 I have a Freqrol A024 1.5k driving my Bridgeport and the things they say in
this case are true... to use these units (Freqrols) as phase converters as
well as frequency controllers means that you have to get a unit rated twice
as high as the load in my case the 1hp motor (.75k) needs a 1.5k freqrol...
the A024 is UL approved and has a low noise mode (that works very well) that
the U100 line does not offer... the U-100 in north america is sold as an OEM
unit in volume only and is then made a part of other equipment (it is used
in commercial airconditioning I think) and hence not avail to you or I

price... SRP last june was $950 on the a024-1.5 and it cost me about $600
>from  an electrical wholesailer for comparison SRP on a FR A024 3.7k is 1275
for a 2.2k 1105

as to using it It is great! I could not be happier... total control of
spindle speed is just the start with these things ask any questions and i
will try to answer.

~R
________________________________________________________
Randolph Lee    [email-masked]  [email-masked]
Tag space For rent!.... Inquire Above for atractive rates!

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From: [email-masked] (Randy Lee)
Date: Fri, 7 Oct 94 19:50:47 GMT

I have had several emails asking for more info on these Mitsubishi Freqrol
units and perhaps this would be of general interest.

on the the features list for the A-024...among other things...

it is a  Sinusoidal PWM control (high carrier Frequency)  V?F control, and
general purpose Magnetic Flux vector control.

there are more than 90 user settable parameters that may be controled by
either the parameter control unit (about the size of a credit card
calculator and able to be remote mounted from the inverter via either a 3m
or 5 m or 10m cable) or by computer control.

RF noise... they offer several filters as acc. but I have not found them
needed it does not interfere with the shop TV of Radio on FM and I seldom
use AM radio any more...

Starting torque of 200%(6hz) regardless of the maker of the motor(Mitsubishi
speed control motors are quoted at 280%)

Ultra low acoustic noise Operation capability (a major +++ this feature can
be turned off for a touch (10% or so) more eff. and even then it is far
quieter than my the old PhaseOmatic but the level of quiet with this feature
enabled is worth many $$$ to my peace of mind over the forthcoming years of
use.)

Highspeed tripless function and restart after momentary power interruption
function as standard

Regenerative Brake resistor as well as DC dynamic Breaking (I use the latter
(it will stop from 3000 rpm in about 3 sec the way I have it set now... ramp
up and down curves are user designable) but the former is available as an
acc. for really quick stops

output Freq range... standard default 0.5hz to 120hz... I seldom use less
than 20hz and that just for a few min at a time... not because I have seen a
problem but because I am conservative by nature and the beltshifting on J
head is quite easy... if I am in production mode where the spindle will be
spinning most of the day I make an effort to keep the Hz between 35 and 85
hz just cause it 'feels better' It can go up to 400 hz and down to 0.2 hz
but this only recommended for new tech. motors designed for this sort of
service such as those that Mitsubishi themselves make for speed control.

on my Bridgeport I use an expanded version(10 to 120hz by 5hz steps) of this
chart to set speed. interpolating as needed for exact spindle speed.hz maybe
commanded to a res of xx.x for fine speed control if needed when used with
an automatic facing head the ramp down of the spindle speed can be matched
to the dia change rate of the head as the cutter increases it's path
outwards from the center. on a lathe this feature may me used to increase
spindle speed in tandem with the depth of the cutoff or faceing tool.

  Spindle speeds  
Belt position    
  Direct drive  
        15 Hz  30 Hz   60 Hz   120 Hz
one     165     330     660     1320
two     279     558     1115    2230
three   438     875     1750    3500
four    680     1360    2720    5440
    
  Back gear  
        15 Hz   30 Hz   60 Hz   120 Hz
one     20      40      80      160
two     34      68      135     270
three   53      105     210     420
four    81      163     325     650

talks with both Faibanks (the builder of the motor on my mill) and
Mitsubishi have convinced me that operation between say 30hz and 120 hz is
just fine as far as the motor is concerned. continuous operation at low Hz
requires that you keep an eye on the temp. the motor is running at but there
is an auto heat trip on it (it has never gone off) I find that I can keep
the belt in position 2 for most of what I do as that gives me a continuous
set of speeds from about 35rpm to over 2200... just by the fliping in and
out the back gears. the spindle drive should not be used at spindle revs
over 2000 I am told so I hand feed at the higher speeds I have used it for
drilling very small holes in brass at the 5440 speed with out any problem.

the fast spindle breaking (sort of auto 'plugging I guess the Hz are
smoothly ramped down to 0 and a user selected rate) is a joy for tool
changing and setting the boring tool. Jog would be of more use were I using
it on the lathe.

Now as to where to get them I contacted Mitsubishi (ask for controls div.)
at 708-860-4210 and was sent brochures and passed on to my local
distributor... using my letterhead I was able to get about 10% off the
original 700 asking price by asking to buy an evaluation unit (one that had
not had the UL approval sticker applied... this was fine with me and my
insurance company has signed off on it  but do check with your insurer
before installing non UL equipment in your house.

BTW the dist. for the NE area is Empire Electrical in either Medford MA
800-225-3405 or Manchester NH 800-649-5504.also look in the yellow pages
under Electric Motor Controls Whol @ Mfrs

To be on the safe side I ran a separate 220 1 phase 20 amp line from the
breaker to the unit although for the 1.5k a 15amp would be OK. I always
overbuild.

~R