Re: Curtis controller model numbers

[Otmar <otlists@evcl.com>]

James Massey wrote:

>Hi all
>
>We have in for repair a couple of Curtis 1209B-7204 controllers, rated as
>72-120V, 275A.
>
>Q1) Do Curtis rate controllers on motor amps, battery amps, or both the same?

Motor amps, which never exceeds battery amps.

>Q2) Does anyone have data on what this controller is supposed to do?

PWM the output to control a series motor. The rest is safety and protection.

>the
>customer has an OEM connection drawing, showing the 4 power terminals, a
>2-wire pot and a control wire on the 3rd terminal - but it fails to show
>where the other end of this control goes to! we suspect it is switched B+
>w.r.t. B-, but can someone help?

Control wire is called KSI and it goes to B+ to turn the controller on.

>Q3) Those of you who have had Curtis failiures, what failed and do you know
>why?

#1) Water in the unit
#2) freewheel diodes overheat, short and blow the fets. The current 
limit has no control below 10% duty cycle on the "B" models and 
therefore can not maintain safe currents with a low resistance motor 
and high voltage pack at stall. This makes the diodes overheat.

>As an aid to repair we are drawing up the circuit.

I did that 10 years ago on a 1221B. (wow! has it been that long!) 
Later Rich Rudman cleaned and corrected what I scribbled. I believe 
the control board of the 1209 is very similar if not identical to the 
1221.

Rich, have you got an electronic copy handy? A gif would be great, 
but if you have the OrCad file I think I could get someone to distill 
it into pdf.

-Otmar-
http://www.evcl.com/914  My electric 914

http://www.CafeElectric.com
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