motor help

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tryin

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a 3 phase 230 volt with a 10 hp AND A name plate FLC OF 23 REQUIRES A (blank)amp FEEDER??????
If I multiply the 23 (because it is the name plate given) by 115% (becasue there isn't any service factor given) I get 26 amps,

If I go to the HP chart and locate the 10 hp and see it needs a 28 amp factor and multiply that by 115% I wind up with 32.

None of these are a choice, What am I doing wrong?
 
tryin said:
a 3 phase 230 volt with a 10 hp AND A name plate FLC OF 23 REQUIRES A (blank)amp FEEDER??????
If I multiply the 23 (because it is the name plate given) by 115% (becasue there isn't any service factor given) I get 26 amps,

If I go to the HP chart and locate the 10 hp and see it needs a 28 amp factor and multiply that by 115% I wind up with 32.

None of these are a choice, What am I doing wrong?
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I hate these questions. What are your choices?

I would say it needs a 30 amp feeder.
 
Dennis Alwon said:
Thanks Carl.... So we then would use 28 amps and multiply by 1.25... I was using 23 * 1.25
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For standard stuff - normal three phase (NEC 2005)

conductors 430.6.A.1 - generally 125% of the NEC table value

(For no SF listed on the nameplate)
Ovld 430.32.A.1 - 115% nameplate FLA
not too exceed 430.32.C - 130%

Branch circuit OCPD (short ckt and GF protection) T430.52 and the rest of 430.52 - depending on what you are using, could be anywhere from 300% FLC to 1300%.

I can't tell if the term "FLC" means nameplate or NEC table current. However, since the term "Full-Load Current" is used in the tables, as opposed to the term "nameplate Full-Load Current" in ovld sizing, I tend to think the code means the table curent, not the nameplate current.

carl
 
coulter said:
For standard stuff - normal three phase (NEC 2005)

conductors 430.6.A.1 - generally 125% of the NEC table value

(For no SF listed on the nameplate)
Ovld 430.32.A.1 - 115% nameplate FLA
not too exceed 430.32.C - 130%

Branch circuit OCPD (short ckt and GF protection) T430.52 and the rest of 430.52 - depending on what you are using, could be anywhere from 300% FLC to 1300%.

I can't tell if the term "FLC" means nameplate or NEC table current. However, since the term "Full-Load Current" is used in the tables, as opposed to the term "nameplate Full-Load Current" in ovld sizing, I tend to think the code means the table curent, not the nameplate current.

carl
Click to expand...
I would never set an overload more than 115% OF FLA /FLC ask me why??
 
quogueelectric said:
I would never set an overload more than 115% OF FLA /FLC ask me why??
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For an sf 1.15, I rarely set the ovld less than 140%.

I've only had one burnup from overload in my carreer. The 100hp motor was on a mechanical debarker. The load was controlled by hydraulic pressure on the debarker knives. The foreman had been complaining the motor ovlds would trip occasionally - he wanted the ovlds set up. We tested the motor, connections, overloads - nothing wrong. I suggested they back off the hydraulic pressureto the mfg rated setpoint.

So, one night the crew tripped the overloads three times in one hour. The fourth time they started the motor - the smoke came out. My response was "I don't see a problem. Sounds like everything worked exactly as per design."

Setting the overloads down would not have changed anything.

carl
 
tryin said:
a 3 phase 230 volt with a 10 hp AND A name plate FLC OF 23 REQUIRES A (blank)amp FEEDER??????
If I multiply the 23 (because it is the name plate given) by 115% (becasue there isn't any service factor given) I get 26 amps,

If I go to the HP chart and locate the 10 hp and see it needs a 28 amp factor and multiply that by 115% I wind up with 32.

None of these are a choice, What am I doing wrong?
Click to expand...

Table 430.250 lists 28A for 10HP @230V. Feeder should be sized for 125% of this value.

Overload is set as per the manufacturers table values based on the 23A nameplate value given. Do not adjust this value as the tables will take care of adjustments. There are several different tables to suit the application, such as motor/controller at different ambient temperatures, service factor, motor design characteristics, etc.
 
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