# Toshiba Short Circuit on Decel Error



## just the cowboy (Sep 4, 2013)

If one has more coast when winding down you may have to change your time, it can relate to field feedback if it has any coast. we have centf pumps that do that 4 the same but still differant


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## JRaef (Mar 23, 2009)

LOL, it so happens I wrote that manual.

SSd does NOT mean there is a Short "Circuit", SSd is the indication of there being a Shorted SCR, different thing. A shorted SCR means it is NOT capable of stopping the flow of electricity, i.e. it is now a full time conductor. The only way to detect that is by measuring the voltage drop across the SCR and if it is too low, that means it is conducting when you have NOT told it to conduct any longer. Unfortunately, it cannot tell exactly WHY there is no voltage drop across the SCR, only that the condition exists, and for the sake of safety, the ASSUMPTION is that it is because there is a shorted SCR.

When you get a false indication, it's a timing issue with that soft starter. If, at the very end of the Decel ramp, you have the Decel Shutoff Voltage (F026) set too low, the starter will take it right down to zero if you ask it to. But if the control system is still active and you remove the Run command input too soon, it can misinterpret that as being a shorted SCR. The cure is to never set the final Decel Shutoff Votlage to zero (or too low), and there is absolutely no reason to do so. At some point LONG before that, the pump ceased to pump, the check valve has closed, and there is no point in keeping on lowering the voltage, you just turn it off. What you want is for F026 to be just low enough to allow the check valve to close gently.

If you have a contactor in line with the soft starter somewhere, opening the contactor before the starter is turned completely off will do the same thing. Not a Bypass Contactor, which is built-in to this starter, I'm talking about a line (or load) isolation contactor. If that's the case, you have to adjust the timing of when that contactor opens up, or again, adjust the Decel Shutoff Voltage to be a little higher.


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## Fixastang (Sep 4, 2012)

*Decel Error*



JRaef said:


> LOL, it so happens I wrote that manual.
> 
> SSd does NOT mean there is a Short "Circuit", SSd is the indication of there being a Shorted SCR, different thing. A shorted SCR means it is NOT capable of stopping the flow of electricity, i.e. it is now a full time conductor. The only way to detect that is by measuring the voltage drop across the SCR and if it is too low, that means it is conducting when you have NOT told it to conduct any longer. Unfortunately, it cannot tell exactly WHY there is no voltage drop across the SCR, only that the condition exists, and for the sake of safety, the ASSUMPTION is that it is because there is a shorted SCR.
> 
> ...


JRaef,

Thank you for the clarification on this matter. I have been fighting this problem for over 5 months and have swapped out this drive twice, sending it back to Toshiba only to have them send it back to me stating nothing is wrong.

Do you have a recommendation on a possible setting for F026?

Thanks again!!!!:thumbsup:


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## JRaef (Mar 23, 2009)

Fixastang said:


> JRaef,
> 
> Thank you for the clarification on this matter. I have been fighting this problem for over 5 months and have swapped out this drive twice, sending it back to Toshiba only to have them send it back to me stating nothing is wrong.
> 
> ...


You need a volt meter and an ear. Watch the RMS voltage drop on Decel and when you hear the check valve close, take note of the voltage, then calculate the percentage do full Voltahe and set that into F026, but honestly, I just always did it just by ear. If the check valve closes and it is still decelling, raise F026 by an RCH. Or in your case raise it until the problem goes away, but not to when the valve starts to slam.


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## adamc (Sep 27, 2013)

also "Check" the check valve, years ago
we had one sticking , getting a similar error code as the impeller was trying to rotate backwards, 
due to the messed up check valve

not a guaranteeing move, but easy to do


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