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Old 08-13-2005, 06:19 PM
GHNorfleet's Avatar
GHNorfleet GHNorfleet is offline
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Location: Woodlawn, Tennessee
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VFD & 3 Phase Motor vs DC Drive & DC Motor, Opinions on Each Set Up

I have been using the DC Motor Controls with the DC motors and have not had any trouble out of them so far. I have been researching the VFD Drives that will convert single phase into 3 phase and will run a 3 phase motor with variable speed. From what I have learned so far, you will have more torque with the 3 phase set up than the DC set up and I cannot comment on the VFD set up as I have not used them. I can comment on the DC set up. I use the NEMA 4 boxes which are wash down units, meaning that they can be used in harsh environments where dust and dirt etc.. abound, expecially in knife shops. These units can be washed down as they have seals around the perimeter of the DC controls and are made for these type of conditions. My research reveals that a TECO-WESTINGHOUSE FM-100 VFD Drive needs the following environment:
�� Mount the unit vertically.
�� Environment ambient temperature should be within 14oF ~ 104oF (-10oC ~ 40oC).
�� Avoid placing the Inverter close to any heating equipment.
�� Avoid dripping water and humid environments.
�� Avoid direct sunlight.
�� Avoid oil, grease and gas.
�� Avoid contact with corrosive gases and liquids.
�� Prevent foreign dusts, flocks, or metal scraps from contacting the Inverter.
�� Avoid electric magnetic interference (soldering or power machinery).
�� Avoid excessive vibration. If vibration cannot be avoided, an anti-vibration mounting
device should be installed to reduce vibration.
�� If the Inverter is installed in an enclosed control panel, please add additional cooling
using an external fan. This will allow additional airflow and cooling.
�� Placement of external fans should be directly over the top of the Inverter.
�� For proper installation of the Inverter, you must place the front side of the Inverter facing
front and the top of the Inverter in the up direction for proper heat dissipation.

This was taken from the manual which I downloaded. I am not knocking the VFD Set up, I just want to know if it would be safe in a knife shop setting where dust and metal scraps would be everywhere, or at least until the shop was cleaned up, I am very interested in using this type of set up but and waiting until I hear from some of you out there that are using this type of set up to see if it is safe or would be a problem in a knife shop.

Any and all comments are taken very serious as I am really interested in this type of set up and they also seem to be cheaper than the DC set up. I personally have not spent a lot on my DC set ups as I have found new controllers on ebay which sold for 10% of what a new unit would cost and DC motors that would normally run over $1000 for around $250 or less depending on the H. P. of the motor, but if you were to buy a good DC set up with a 2 HP motor and a matching controller, you would have to spend around the $1250 or more mark for a new set up. Any and all comments are very much appreciated!

Gilbert H. Norfleet, Jr.
Norfleet Custom Knives
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Old 08-13-2005, 06:39 PM
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Ray Rogers Ray Rogers is offline
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I can't do much to help you directly since I have not used a VFD set up but I have heard the following:

I haven't seen any bad comments from guys who have used them

Rob Frink of Beaumont Metal Works, makers of the KMG Grinder, have reportedly stopped selling DC set ups for the KMG and switched to VFD. Presumably, Rob reseached this pretty thoroghly because he's that kind of guy. If I were you, I'd contact Rob directly and get the info on VFD from the only guy I know of who supplies those set ups specifically for use in knife makers shops....


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Old 08-13-2005, 07:07 PM
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Don Cowles Don Cowles is offline
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I have the VFD on my KMG, and a DC variable drive on my Burr King. In all honesty, there is virtually no difference in perfomance in this application, at least in my personal experience. Your mileage may vary...


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Old 08-13-2005, 08:10 PM
philip bradford philip bradford is offline
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I have both VFDs that Rob sells. The 2 hp on my KMG the 1 1/2 on my horizontal edge finsher (also by Rob) with the extention table. While I have not findled with the internal contols of the KB contoller, you can adjust many of the motors features. For example, you can adjust how fast the belt starts and stops, maximum speed, torque, etc. Rob was nice enough to adjust mine for me, and it has run flawlessly. I like for the motor to stop the instant I flip the switch. It may sound silly, but I don't like to wait 30 seconds for the belt to stop spinning when I need to change to a different grit. I believe they are also more effecient than traditional dc motors. The controllers are rated as washdown, althought you will need to purchase your own washdown rated connectors if you really plan on needing this feature, otherwise they are very, very, resistant to shop type environments. The motors are Lesson and TEFC. There are only two drawbacks as I see it, first, there are allot of wires you must hookup (8 I believe). Second, I can't sleep at night if I don't unplug these motors. It's very hard to sleep at night knowing one lightening strike could cost me $1,400.


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Old 08-15-2005, 05:15 PM
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Tom Militano Tom Militano is offline
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Your not the only one that worries about lightening cooking machinery. The only thing that stays plugged in when I'm done for the day is the radio. Lightening blew the top out of a tree near the shop about ten days ago and probably would have cooked a motor or two if they were plugged in. It did fry the radio, but I had a spare.

Tom Militano
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Old 08-16-2005, 08:26 AM
PaulD PaulD is offline
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My short experience with VFD systems was in industrial laundry applications. these were General Electric units with matching motors in the 10 to 20 HP range. The VFD electronics were mounted on the machines with some shock absorbing and minimal shielding.

Commercial laundrys are an extremly nasty enviroment, hot, humid, the machines vibrate violently and most places are amazingly dirty. The many machines in use cause the AC lines to be noisy at best and have large voltage swings (spikes) in most cases.

Most of the failures I saw were due to problems in the mechanical drives or the motors themselves, with resulting failure of the VFD electronics also.

The most common maintainance system was "run it till it quits"

The VFD gave the manufacturer more operational features (most of which the user didn't use) without complicated electro-mechanical support. The user got faster machines that used less electricty and in general were easier to maintain. The service technician got the added troubleshooting problem of attempting to determine what the initial failure cause was.

I would believe that the main benefit for a grinder application would be some increased torque, better speed control at varying loads and slightly less electric costs. The most times complicated programing features are not required. I see the greatest advantage being the torque/current limiting feature as a motor saver.

The quick stop function is a nice safety thing but in my opinion, the long term cost/value thing has yet to be determined. Perhaps Rob Frink can add some insight as he probably has the most experience and user feedback.

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