Inrush current on 200 HP induction 460v motor

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FER3

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I have a new 200hp 460v motor, premieum efficiency, 226 fla , 1800 rpm, 1.15 SF
PF= 86.7, Code F, (4.67). Distance from breaker to starter 30 feet, distance to motor from starter 5 feet, I know the OL for starter, VD using 350mcm is 0.4 or 0.1%. My question is: will 350mcm 75 degree cable be suitable for this application, taking into consideration the inrush-current? Breaker is 600amp frame with 300 amp trip.
 
At 86% PF a 350 kmlil would not meet the minimum conductor ampacity as required by NEC for an ACL application.
For a drive application, the answer would depend on the drive specs.
 
markstg said:
350's will work. No need to take into account inrush current on cable sizing.
Click to expand...
Might I ask what numbers you used to come to that conclusion.
Taking into account the PF correction mentioned at the bottom of 430.250, I arrived at a different answer.
 
FER3 said:
I have a new 200hp 460v motor, premieum efficiency, 226 fla , 1800 rpm, 1.15 SF
PF= 86.7, Code F, (4.67). Distance from breaker to starter 30 feet, distance to motor from starter 5 feet, I know the OL for starter, VD using 350mcm is 0.4 or 0.1%. My question is: will 350mcm 75 degree cable be suitable for this application, taking into consideration the inrush-current? Breaker is 600amp frame with 300 amp trip.
Click to expand...


Code F corresponds to 5 to 5.6kVA/hp.

So using 5.3kVA/hp, locked rotor kVA is 1060, so on a 3ph 460v...
(1060kVA/0.46kV/sqrt3) = 1330A.

Trip delay setting would depend on what you're trying to turn I suppose.
 
augie47 said:
Taking into account the PF correction mentioned at the bottom of 430.250, I arrived at a different answer.
Click to expand...

If you look closely, you will notice that the pesky little asterisk only applies to FLA of synchronous motors. My handy C-H slide says 350s are the choice.
 
Ahhh.,...live and learn,, you are correct. I will agree that 350s will work. (Drive name plate may change my answer)
 
augie47 said:
At 86% PF a 350 kmlil would not meet the minimum conductor ampacity as required by NEC for an ACL application.
For a drive application, the answer would depend on the drive specs.
Click to expand...

Augie
I never doubt you opinion, but this time why not?
Never mind. I'm too slow.
 
bob said:
Augie
I never doubt you opinion, but this time why not?
Click to expand...

ALWAYS doubt my opinion. I often do:grin: and I hope others will also
I was incorrect. I read too much into the question and added a power factor correction when I should not have as pointed out by dkidd.
Unless I am overlooking something (else) 350s should be allowable.
 
OK, I'm not sure why you are concerned with inrush. It usually it is only a concern if the motor is a large load on a generator or transformer. As Augie47 said, if the motor is on a VFD, the VFD requirements would need to be complied with. The conductor size and short circuit protection would be dictated by the NEC table (with exceptions for the short circuit device rating if starting is an issue). The overload protection would be based on the actual nameplate ampacity. Would you please explain your concern about inrush? A number of electrical equipment manufacturers have slide rules that give good information for most common applications.
 
There is only one thing you need to look at for motor lead selection;: Motor nameplate FLA. You must select cable sized to handle at least 125% of the motor nameplate FLA.

Oh and distance from the starter to the motor for determining Voltage Drop... So OK two things. There are only two things you need to look at for motor lead selection: 125% of motor nameplate FLA and distance for determining Voltage Drop.

And temperature ratings... OK, Three things. There are only three things you need to consider for motor lead selection: 125% of motor nameplate FLA, distance for determining Voltage Drop and temperature.

And number of conductors in the conduit... OK OK FOUR THINGS! There are only 4 things you need to look at for motor lead selection: 125% of motor nameplate FLA, distance for determining Voltage Drop, temperature and number of conductors in the conduit. ...

My point before I got carried away with the joke is that "inrush current" is not one of the selection criteria.

Apologies to Monty Python..
 
Jraef said:
There is only one thing you need to look at for motor lead selection;: Motor nameplate FLA. You must select cable sized to handle at least 125% of the motor nameplate FLA.
Click to expand...

Wrong. You must use the NEC tables.
 
Inrush current on 200 HP induction 460V motor

Inrush current on 200 HP induction 460V motor

Electric-Light said:
Code F corresponds to 5 to 5.6kVA/hp.

So using 5.3kVA/hp, locked rotor kVA is 1060, so on a 3ph 460v...
(1060kVA/0.46kV/sqrt3) = 1330A.

Trip delay setting would depend on what you're trying to turn I suppose.
Click to expand...

This verticel motor is for a direct couple to a water pump. The Name plate listed a Code "F" with (4.67) KVA/hp beside it. I know this does not correspond to the standard code. Taking all of this into consideration, the length of run 30 feet to the starter and 5 feet to the motor, the voltage drop is nothing. The 350mcm meets all NEC standards and the inrush is what is concerning me. Is this border line or acceptable as is using 350mcm cable?
 
FER3 said:
This verticel motor is for a direct couple to a water pump. The Name plate listed a Code "F" with (4.67) KVA/hp beside it. I know this does not correspond to the standard code. Taking all of this into consideration, the length of run 30 feet to the starter and 5 feet to the motor, the voltage drop is nothing. The 350mcm meets all NEC standards and the inrush is what is concerning me. Is this border line or acceptable as is using 350mcm cable?
Click to expand...

Starting torque is very little for centrifugal pumps and the impeller is not a high inertia load, so starting torque or extended acceleration causing extended greater than FLA draw aren't issues. Sounds like you're good to go.
 
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