On 12/24/2020 02:18 AM, Chris Albertson wrote:
"All the time?" When you have a hard requirement like this is when some
detailed engineering can pay off. Assume you are reversing at 50% duty
cycle and burning 1KW 50% of the time. Where I live this can cost 12
cents per hour. This is $89 per month if you actually do run "all the
time". Or $1,000 per year. Or maybe you are usig a lower value resister
and burning 4KW with your brake? That is $4K per year
The VFD only turns the braking resistor on when the DC link
voltage rises above some limit due to energy returned from
the motor during deceleration. I never detect any warming
on mine except during rigid tapping cycles.
A better way is to use a battery inside the power supply. a 100 amp-hour
lithium battery would cost possibly $400.
You are going to need a 340 V battery bank, and a charger
for it.
Jon
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