On 12/22/2020 06:30 PM, Matthew Herd wrote:
In my research on resistor sizing, I heard reports that Haas uses stove
elements for their braking resistors. On factory machines, no less. Of course
that’s second hand, so I can’t say it’s true.
Yes, absolutely. Our Haas at work has a stovetop element in
a screen guard on the back of the machine.
All of them are made like that. It is a perfect solution
for a 240 V machine. But, for the smaller VFDs you want a
small stovetop element so it doesn't draw excessive
current. Assuming a voltage doubler on a
120 V VFD, it will still have 340V or so DC on the DC link,
same as a 240 V VFD. A 40 Ohm element should draw less than
10 A, which should be safe for anything but the smallest
VFD. So, get the 7" stovetop elements, not the 11" ones.
Using too low a resistance won't harm the MOTOR, it will
blow the power brick in the VFD.
Jon
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