5HP 230v drive brake resistors

I have a milling machine that I acquired cheaply, due to a failed sipndle VFD drive and burned out brake resistors.
The drive was professionally repaired and works great.
However, I am a little puzzled by the brake resistors. Yaskawa manual only lists part numbers. I would like to find some suitable replacements. What I need to know if the recommended ohms and watts. I have some big-ass resistors in my ebay store that look like they might fit, but I have no way of ascertaining what ohms/watts I need.
Thanks
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I looked up some data, it looks like I need 40 Ohm, 392 watt resistor, so I bought two 20 Ohm, 300 watt resistors on ebay, that should do it.
i

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300 watt is probably going to be too low of wattage.
Electric water elements can be used in a pinch...
--just be sure and buy the kind that won't be damaged if they are operated while not submerged.
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That's two 300 watt resistors == 600 watt combined.
i

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On Tue, 23 Oct 2012 21:02:02 -0500, Ignoramus15542

300 watts is what Yaskawa calls for on a 5hp VFD at 230 volts.
Gunner, who works a LOT with Yaskwa drives (no matter what label is on them)
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On 10/23/2012 8:14 PM, Gunner wrote:

The exact value of these resistors isn't really critical - we're just dumping power into them to slow the motor...
When I need a power resistor like this I go to the hardware store and get an element for a radiant heater - one of those ceramic cone jobbies that's 600 watts or so at 120 volts and cheap as dirt.
They'll dissipate 600 watts practically forever (and motor braking isn't a constant) and work out to about 24 ohms. Close enough for most any braking application.
Carla
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On Tue, 23 Oct 2012 21:10:38 -0700, Carla Fong

Thanks for the heads up! Ive never seen a radiant heater like that..but then..I live in California.
Gunner

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On 10/23/2012 9:24 PM, Gunner wrote:

Actually you probably have... I just described it poorly.
See <http://www.porticus.org/bell/pdf/415-120_heater.pdf
Carla
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On Wed, 24 Oct 2012 15:47:59 -0700, Carla Fong

Cool! Ive never seen one of those before!
Gunner
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Many years ago my dad brought up a new radar station at White Sands. It was a new design - a target tracking (automatic) radar.
Since the manufacture of the output tubes didn't want to drive the antenna when testing the transmitter and verifying specs.
It was determined that a number (N) 1000 watt light bulbs to be used.
That was great, the transmitter was harsh on start up currents and liked to over drive the filaments - new sets were pulled from stores every other day for several weeks. Then it stopped and the real antenna was attached for other tests. The purchasing guy had stocked up on a volume discount deal - and then found out the bulbs went back to the light poles.
Dummy loads are just an energy dump. The idea is to have the resistance near the value needed so to much current won't be drawn and not to high to prevent the power dump.
Martin
On 10/24/2012 5:47 PM, Carla Fong wrote:

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Why not immerse them in oil? Mineral oil will work.
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No thanks, I do not want a source ofa fire.
i
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writes:

Use to keep your coffee warm.
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If they are ANYWHERE near flash, you are doing something wrong.
And if that worried, buy a gallon of silicon such as DOT-5 brake fluid with a 400F flash point <http://www.technicalchemical.com/msds/7012-6.pdf
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David Lesher wrote:

Or use a bigger braking resistor:
http://imgur.com/HvffT
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On Mon, 22 Oct 2012 19:20:01 -0500, Ignoramus21608

Which VFD is on the drive?
Gunner
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Yaskawa 5 HP 230v
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On Mon, 22 Oct 2012 21:57:40 -0500, Ignoramus21608

Standard PC-3?
That should take a 30 ohm 500 watt resistor.
Gunner
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wrote:

You can probably get away with using this one
http://www.ebay.com/itm/Aluminum-Encased-Braking-Resistor-500-Watt-20-ohm-/271087495712
since the mill wont be stopping as fast as the lathes I program the Yaskawa VFDs to do.
Omniturn gets $150 for the 30 ohm duplicate btw.
And you CAN get away using a 250 watt, if you blow a muffin fan over the resistor while the spindle/tool changer is in operation, in a small well vented box.
Gunner
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Ignoramus21608 wrote:

OK, assume the machine is 240 V. The DC bus voltage will be roughly 340 V DC. To stop the motor at normal 5 Hp rating, that is ~ 3700 W. 3700/340 = 10.9 A. So, a good choice would be a resistor bank that draws 11 A at 340 V, or 31 Ohms. It will dissipate a peak of 3700 W, but the average will be much lower. So, probably a couple hundred Watts of resistor should handle it, even in rigid tapping duty, otherwise it will never even get warm. You could put 3 100 Ohm resistors in parallel, or 3 10 Ohm resistors in series.
Jon
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