Dynisco ATC 990 - Page 12

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For!example,!in!a !proces s!with!these!conditions!set:!Setpoint=6000;!Pr essure!Stand‐by!T hreshold!= 200 !Stand‐ by!Recovery!
Time=30seconds;!Stand‐by!Acti ve!Limit=20.0!and!Integral!Time(Ti)=10seconds!
1. Sta nd‐by!begi ns!immediatel y!at !SP+Threshold!(6200) !or!SP‐Threshold!(5800).!
2. If!normal!input!returns!( within!band!o f!58 01!to!6199 )!in!less!that!the!recovery!time,!normal!power!resumes!after!2.5x!
the!int egral!time!(25s).!
3. If!normal!input!does!not!resum e!in!in!less!that!the!recovery!time,!0%!manual! mode!power!is!applied.!The!user!m ust!
return!the !contro ller!to!automa tic!mode!and!allow!a!new!stead y!state! power!to!be!store d!before!the!feature!can!
become!active!ag ain.!
4. If!the!r ecovery!time=OFF,!manu al!mode!is!instantly!applied, !with!power!set!to!the!steady!state!value.!
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For!a!s table!(steady!state)!cond ition,!the!proc ess! value!must!be!inside! the!req uested!band![Setpoint!±Pres sure!Stand ‐by!
Threshold ]!for!more!than!one!minute.!The!power!level!needed!to!achieve!the!stable!condition! is!called!the!steady!state!value.!
See#fig ure# 1a#below.#
Once!calculated!the!stored!value!rema ins!unchanged!until!there!is!a!change!of!the!setpoint ,!or!the !contro ller!is!changed!from!
autom atic!to!manual!mode.!If!t his!happens,!a!new!steady!state !value!mus t!be!found,!an d!the!automatic!stand‐by!feature!
cannot!function!until!it!has!been!stored.!!
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In!addition!to!the!au tomatic!stand‐by!feature!itself,!further!protection!to! the!process!is! given!b y!the!Stand‐by!Active!Limit.!Its!
purpose!is!to! limit!the!output!swin g!possible! in!very! sensitive!react ing! pressure!process.!This!works!by!limiting!the!power!
applied!to!the!process!to!not!more/less!than! the!stored!steady!state!value!±!the!Stand‐by!Activ e!Limit!set!by!the! user.!See#
figure#1b#above.#
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If!the!stored!steady!state!value=50%!and!stan d‐by!active!limit=20%,!th e!overall!limits!would!be!30%!to!70%.!
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