Bad Motor Protective Settings

7/21/2019 Bad Motor Protective Settings

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Why Can’t I Start MyMotor? Lessons LearnedFrom Bad Motor Protective

Settings Terrence Smith

Jeyanth Yogaratnam Thomas Ernst

E !igita" Energy

Te#as $%M &e"ay Con'erence ()*+



Motor Inhi,it



Thermal Capacity required toStart

Thermal Capacity used due toOverload

When the motor has cooledand the level of thermalcapacity used has fallen to66%, a start will bepermitted.

f the motor had beenrunnin! in an overloadcondition prior to stoppin!,

the thermal capacity wouldbe some value" say #$%.

or e&ample, if the T'()*+C+-+CT /S(0 for the last 1starts is 23, 24, 25, 21, and2% respectively, the(+)7(0 ST+)T78 C+-+CTis 25% 9 .21 : 44.51% used.

f *otor is Stopped;

TC- . Start Inhi,it E#am/"e



TC- enerated !0ring aStart



TC- enerated !0ring aStart



Case St0dy1

Start Inhi,it Set Too2igh



Case St0dy1 Start Inhi,it Set Too 2igh

Fac0"ty had a high inertia "oad 3ith a

"earned TC- at start o' 456

Start Inhi,it Margin 3as set at (+6

TC- has to 'a"" to *))7458*9(+:(9+6 ,e'orea start is a""o3ed

$ more "i,era" setting o' +6 3o0"d have

a""o3ed a restart at *56 TC-



Case St0dy1 Start Inhi,it Set Too 2ighLessons Learned

Start Inhi,it needs to match the a//"ication

With high inertia motor a//"ications;ena,"ing the start inhi,it 'eat0re is nothe"/'0"

I' the motor start TC- is a reasona,"e "eve"<s0ch as "ess than =)6>; it is a"3aysrecommend to ena,"e the start inhi,it'0nction 3ith reasona,"e TC- 0sed marginsetting to /revent 0nnecessary start inhi,it



Case St0dy1

Coo"ing Time

Constants Set asCoo"ing Times



Case St0dy1 Coo"ing TimeConstants Set as Coo"ing TimesFaci"ity 'o0nd coo"ing times o' =) min0tes

<co"d> and*(+ min0tes <hot>@999

$nd set these times as coo"ing timeconstants in the motor re"ay

This "ay dormant 'or severa" years@@

-nti" a tri/ occ0rred



Case St0dy1 Coo"ing TimeConstants Set as Coo"ing TimesInhi,it 3as set to (+6

3ith a "earned start TC- o' ==6

TC- has to 'a"" to (A6to start

With coo"ing timeconstant sto//ed set to*(+ min0tes; it taes*45 min0tes to coo" to(A6 a'ter a tri/

With the correctcoo"ing time constant



Case St0dy1

2ot.Co"d &atio Set

Incorrect"y



Case St0dy12ot .Co"d &atio SetIncorrect"y

Faci"ity 'o0ndcoo"ing times o'=) min0tes <co"d>and 0ser

erroneo0s"y setthe 2ot.Co"d &atioto *6 rather than546

This com/o0nded



RTD Bias


Settings o' Minim0m;Midd"e; and Ma#im0m

Minim0m designam,ient

Midd"e am,ient D rise Dhots/ot

Ma#im0m ins0"ationrating



RTD Bias


Minim0m : A)C

Midd"e : A)C D ++C D*)C : *)+C

Learned Starting TC- :

4)6

2ot.Co"d : )9*@9++CStator had a TC- o' ()6

2ot.Co"d : )954@++C



Case St0dy1

&estart o' a 2igh Inertia

Load



Case St0dy1&estart o' a 2igh Inertia Load<I! Fan>Motor !ata

Sa'e Sta"" time : (4s .()s

0m,er o'consec0tive starts :

.(

Starting time : +s %4*s 5)6



Case St0dy1&estart o' a 2igh Inertia Load<I! Fan>Lessons Learned

Immediate restart may not ,e avai"a,"e

Go"tage de/endent c0rves he"/ 3ith starting; ,0t not restart

So't starting methods can he"/ the sit0ation

It is necessary to o,tain acc0rate in'ormation a,o0t the motor,e'ore designing the motor re"ay set /oints

In some cases; it is necessary to cons0"t the motorman0'act0rer 3hen it comes to the se"ection o' the over"oadc0rves in an a//"ication 3here the motor starting c0rves and

therma" damage c0rves are very c"ose to one other



Case St0dy1

Hther B"ocing E"ements



Case St0dy1 Hther B"ocingInhi,its

!o not 'orget a,o0t the other ,"ocinge"ements that 3i"" /revent a motor 'romstarting

Starts Per 2o0r Loco0t

Time Bet3een Starts Loco0t



es

I' I have a motor re"ay

3ith a therma" mode"; areother inhi,its rea""y

necessary?



Fina" Tho0ghts on MotorLoco0t The inhi,it margins; i' set too high can /revent atime"y restart o' the motor

Coo"ing time and coo"ing time constants are not thesame thing9 Yo0 m0st no3 3hat va"0e the motorre"ay is e#/ecting; 0s0a""y coo"ing time constant

The ratio o' the hot to co"d sa'e sta"" time aects themotor steady state therma" ca/acity 0sed; 3hichcan aect the motor therma" mode" and inhi,itrestart

2igh inertia "oads 0se "arge 0antities o' therma"ca/acity 0sed d0ring a start9 This re0iressigniKcant coo"ing times in the event o' a tri/9

Starts /er ho0r; restart rate; and time ,et3eenstarts may ,e red0ndant; ,0t is /ro,a,"y necessary

'rom a 3arranty stand/oint



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Bad Motor Protective Settings