Re: Sizing of braking resistors for a VFD

On one of their VFD drive families (not the one I'm using),
Automation Direct recommends:

1HP 200 ohms 80 watts
2HP 100 ohms 300 watts

If I have a 100 ohm 250 watt resistor, do you think that's close
enough for my motor?

1.5 HP 5.7amps, 208 volt 3 phase

Jeff

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>
>
> washcomp wrote:
>
> >I am looking for the proper size dynamic braking resistor for an
> >Omron G5+ VFD.
> >
> >My motor is a 1.5 HP 3 phase 208 volt on my Bridgeport.
> >On their house brand of VFD, Automation direct recommends about
150
> >ohms, 300 watts. Do different drives take different values or is
it
> >strictly based on the motor size?
> >
> >
> Motor size is the most important, since the drive won'd DRAW more
> current from the motor than it will SOURCE to it.
>
> 150 Ohm at 360 V DC will drain about 2.4 A. Is that enough? I
would expect
> the line current on a 1.5 Hp, 208 V motor to be about 5 A. That
could be
> about 1400 W. So, you'd want to be able to dissipate that much
energy
> in the braking resistor. I = P/E =3.89 A, R=E/I = 92 Ohms. I'd
go for
> about
> a 100 Ohm resistor to be sure. I'm pretty confident the VFD can
handle
> 4 A in the braking resistor, for the millisecond periods where it
is needed.
>
> I'm using something like 50 Ohms on my 1 HP drive on my Bridgeport.
>
> Jon