On 12/23/2020 06:55 PM, andrew beck wrote:
Just to tag in.
I need a braking resistor for my cnc mill spindle it's a 7.5kw vfd.
Needs to rigid tap all the time etc
Any ideas? I like the idea of a stove element..
Just need to know some values etc
Get the 11" stove elements. A 2400 W element will draw 10 A
at 240 V, therefore the resistance is
about 23 Ohms. At 340 V DC, the element will draw 14.8 A.
That is probably a safe number, but don't go above that
(higher wattage or lower resistance). Probably a 1700 W
element will work fine, but may not provide quite as much
braking. I'm using two 50 W resistors on my lathe with 5 Hp
motor, and it provides excellent braking, bringing the
spindle to a stop in under one second. But, I am not set up
for rigid tapping, so I don't know how hot it would get
under repeated reversals.
Jon
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