I have an old style Sevcon that wants to see the shaft slow/stop. I had to wait until I was moving at less than 2 knots before the controller would let the motor reverse. The shaft brake I added allows me to fully stop the prop shaft at any speed and switch motor direction immediately.
Denny, did you get the new firmware for your controller?
Mark
--- In electricboats@
>
> Matt's answer is probably the correct explanation for your hesitation but there is another possibility.
>
> Your controller knows the speed and direction of the motor shaft via the hall sensors. It may not give you reverse current until it detects the shaft has stopped moving forward.
>
> I had a real problem with my Sevcon PMAC at first. It took 15 seconds for the boat to stop coasting forward; that is a long time to wait for reverse. Sevcon changed the controller's firmware to fix the problem.
>
> Denny Wolfe
> www.wolfEboats.
>
> ----- Original Message -----
> From: Matthew Geier
> To: electricboats@
> Sent: Thursday, December 24, 2009 4:24 PM
> Subject: Re: [Electric Boats] Forward/ reverse potentiometer.
>
>
>
> ebdrives wrote:
> > Dennis,
> >
> > I use a Merritt Joystick to run my electric 26'powerboat. It runs good to control forward/neutral/
> >
> This may not be the joystick causing the hesitation, it is probably the
> motor controller.
>
> Flipping from forward to reverse would put a lot of strain mechanically
> and electrically on the system, so when you flip the control handle from
> forward to reverse, the motor controller isn't instantly changing
> direction, but ramping the motor speed down at some pre-determined rate
> , stopping and then reversing the fields and ramping up to your throttle
> position.
> These ramp up/down rates are almost certainly programmable.
>
> I'm running a brushed motor and an Alltrax AXE, so reversing is done by
> contractors, but the forward/reverse switch is 3 way, so that 'off' has
> to be passed on the way to reverse, this causes the controller to reset
> and it then 'ramps up' at the programmed rate to the throttle setting it
> reads off the speed pot.
>
> In my case, flipping from forward to reverse with out shutting off
> would result extremely high motor currents as it fought to change
> direction against the high forward inertia of the boat. This would
> almost certainly put my motor into overload and cause the controller to
> go into current limit. It may even cause the reversing contactor to weld
> shut as it closes onto a huge current spike.
>
> So reprogramming the throttle ramp rates on your controller to get a
> 'snapper response' may not actually be a good idea.... (Assuming of
> course, that your controller allows 'in the field' changes to the
> throttle response ramp rates).
>
No comments:
Post a Comment