Re: (ET) More motor controller questions

[Brian Matheny <ws3f norfolk-county com>]

At 05:36 AM 12/15/1999 -0500, you wrote:
>1) When a controller is purchased that is supposed to handle say 48 Volts 
>at
>300 amps what happens when the demand is greater than that?
>Is this current limited by the controller or does it burn out?

Limited.  If the motor inductance is too low however, such as using too
large a motor for the controller, the current can still exceed the ratings.

>Also is there a bypass relay internal to controllers that "short" the fet
>devices under full current ?

No.  The control circuit still needs to be able to control varying loads.

>2)  Are controllers rated at particular duty cycle?  As in the above
>controller... could it do 300 amps all day long
>or is that a peak current for only a few seconds and it can run at say 
>half
>of that long term?

Only a couple of minutes at peak current.  About 40% of rated for long term
if properly heat sinked.  Curtis controller instructions say to bolt it to 
a
large metal surface.

-Brian  30,500+ EV miles since 5/97!  Renewable energy charging, soon!
http://www.ncounty.net/users/ws3f/ws3f.htm