5HP 230v drive brake resistors

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

Which VFD is on the drive?

Gunner

"The best government is a benevolent tyranny tempered by an occasional assassination." --Voltaire

Yaskawa 5 HP 230v

Standard PC-3?

That should take a 30 ohm 500 watt resistor.

Gunner

"The best government is a benevolent tyranny tempered by an occasional assassination." --Voltaire

You can probably get away with using this one

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

"The best government is a benevolent tyranny tempered by an occasional assassination." --Voltaire

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

I bought two 20 ohm 300W resistors and I will connect them in series.

That ought to work. If you have it on the highest speed range and stop, it may not absorb enough energy returned from the motor. If that happens, you might get an over-voltage trip from the VFD. You can slow the speed ramp-down, usually a parameter on the drive, or go to one resistor for a 20 Ohm load. But, probably the 40 Ohms will absorb enough energy and all will be well.

Jon

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.

That's two 300 watt resistors == 600 watt combined.

i

while not submerged.

while not submerged.

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)

while not submerged.

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

I believe that all government is evil, and that trying to improve it is largely a waste of time. But that is certainly not the common American view; the majority of Americans are far more hopeful. When they see an evil they try to remedy it - by peaceful means, if possible, and if not, then by force. - H. L. Mencken

while not submerged.

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

Gunner

One caution - the inductance will be additive - thus go ole XL .

I'd make the windings turn differently when mounting so they don't enforce each others magnetic field.

Not much on 60 cycles or even DC. But the RF edges of the VFD might see it and slow the dv/dt or the second derivative.

Mart> >>

Why not immerse them in oil? Mineral oil will work.

No thanks, I do not want a source ofa fire.

i

Use to keep your coffee warm.

Actually you probably have... I just described it poorly.

See

Carla

I don't understand tongue piercings. If you want a speech impediment that badly, go tell my barber that crewcuts are for pansies.

Cool! Ive never seen one of those before!

Gunner