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field voltage ramp up

PostPosted: Mon Apr 04, 2011 2:25 pm
by MollyBlossom
I have been using your small case alternator #4023 for about a year. I just started using the NS2 regulator. The alternator was fine with my previous external regulator that didn't start to ramp up the field voltage for 90 seconds and then very slowly. The NS2 starts instantly resulting in a very large output current especially if the engine started at 1500 rpm before I could get the throttle down to 1000 rpm. I think this can cause belt slippage. As a result I think this resulted in burning out rectifiers in the alternator. The belt seems tight and I am using one of your recommended belts. Any suggestions? What is the profile of the ramp up in current?

Re: field voltage ramp up

PostPosted: Mon Apr 04, 2011 2:54 pm
by Coulomb
Belt slippage causes heat transfer into the rotor, which will burnout before the diodes. Diode failures are usually the result of high voltage transients, often generated when switches are in series with the alternator output.

In any case, belt slip won't happen from loading the alternator using appropriate belts with proper tension.

You can put a separate switch to the On/Off input to control the regulator as desired.

Re: field voltage ramp up

PostPosted: Mon Apr 04, 2011 4:18 pm
by MollyBlossom
How soon does ramp up start ofter the on/off goes on? How long does ramp up take in order to get full on field current?

Re: field voltage ramp up

PostPosted: Tue Apr 05, 2011 2:28 pm
by Coulomb
It happens in a matter of a few seconds.

Re: field voltage ramp up

PostPosted: Thu Apr 07, 2011 6:03 am
by MollyBlossom
The problem wasn't the alternator or regulator. When I went to put on an alternate alternator I found the positive voltage lead on the alternator was loose. When I tightened it up all is well.

Re: field voltage ramp up

PostPosted: Thu Apr 07, 2011 3:01 pm
by Coulomb
Thanks for letting us know.

You're lucky to have caught the loose connection before it acted like a cutting torch and melted the stud.

After melting the stud, the next likely event is the wire falling against the engine and grounding the battery. If you don't have a battery fuse, then you have a fire.

We've seen the aftermath of this.