3phase / single phase

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happy new year to all,
VA Volts AB BC 3p Pole AT AF
30,200230131.33100200
5,50023023.91350100
9,50023041.30360100
3,30023013.0433050
7502303.2632050
15,26223058.51270100

pls. help me compute the total Current load for this panel board,
the the last load (58.51) will be connected to a single phase Panel board.

thanks you so much
 

kwired

Electron manager
Location
NE Nebraska
Your amperage values do not correspond to the VA values.

The three phase loads need to apply a 1.73 multiplier for correct values.

The single phase load does not match either 15,262/230 = 66.35 ??

Which is correct the VA values or the A values? One or the other is miscalculated.
 
happy new year to all,
VAVolts AB BC 3p Pole AT AF
30,200230131.33100200
5,50023023.91350100
9,50023041.30360100
3,30023013.0433050
7502303.2632050
15,26223066.35270100


pls. help me compute the total Current load for this panel board,
the the last load (58.51) will be connected to a single phase Panel board.

thanks you so much

I = 15,262 watts / 230 volt
= 66.35 amps (total load of single phase panel board attach to 3 phase panel board)

pls. correct if this is wrong.
total load of 3 phase panel board
I total = 1.732 * 66.35 + (.25 * 13.04) + 212.81 ( total load of 3 phase )
= ? ??

thanks for all the HELPPPPP.
 

kwired

Electron manager
Location
NE Nebraska
I = 15,262 watts / 230 volt
= 66.35 amps (total load of single phase panel board attach to 3 phase panel board)

pls. correct if this is wrong.
total load of 3 phase panel board
I total = 1.732 * 66.35 + (.25 * 13.04) + 212.81 ( total load of 3 phase )
= ? ??

thanks for all the HELPPPPP.

Still don't have VA that matches amps for the three phase loads.

take the first load

30,200 VA @ 230 volt 3 phase is not 131.3 amps

30,200/230/1.73= 75.8

30, 200 VA @ 230 volt single phase is 131.3 amps

Is VA correct value or amps the correct value?

do not use the 1.73 factor for the single phase load.

Your total three phase load needs calculated then add the single phase load to the two phases it is connected to the total for those phases.

The total load will be 3 phase amps + single phase amps = amps phase A, 3 phase amps + sinlge phase amps = amps phase B, 3 phase amps = 3 phase amps phase C.

The amps will not be same for all three phases. Total VA will be total VA in your list (if it is calculated correctly)
 
VA is the original value of equipment,

VA Volts AB BC 3p Pole AT AF
30,20023075.803100150
5,50023013.8232050
9,50023023.8733050
3,3002308.2932050
7502301.8832050
15,26223066.35270100
TOTAL66.35123.67


Total 3 phase load = AB(single phase load) + 3phase load
= 66.35 + 123.67
= 190.02 amps

DF @ 85 % = 161.517amps

Main breaker will be 200AT/250AF
 

Smart $

Esteemed Member
Location
Ohio
VA is the original value of equipment,

VA
Volts
AB
BC
3p
Pole
AT
AF
30,200
230
75.80
3
100
150
5,500
230
13.82
3
20
50
9,500
230
23.87
3
30
50
3,300
230
8.29
3
20
50
750
230
1.88
3
20
50
15,262
230
66.35
2
70
100
TOTAL
66.35
123.67



Total 3 phase load = AB(single phase load) + 3phase load
= 66.35 + 123.67
= 190.02 amps

DF @ 85 % = 161.517amps

Main breaker will be 200AT/250AF
Is 230V the nominal voltage of the connected system or the voltage on nameplates?

Typical nominal voltage is 240V. Motors use 230V on their nameplates and in Code tables, but are initially calculated by Code using amperes... then converted to VA... but system loading is then figured at nominal system voltage under Article 220. Not written explicitly, but if you following prescribed Code methods, this is what happens. Amounts to about a 4% difference.
 

kwired

Electron manager
Location
NE Nebraska
VA is the original value of equipment,

VA
Volts
AB
BC
3p
Pole
AT
AF
30,200
230
75.80
3
100
150
5,500
230
13.82
3
20
50
9,500
230
23.87
3
30
50
3,300
230
8.29
3
20
50
750
230
1.88
3
20
50
15,262
230
66.35
2
70
100
TOTAL
66.35
123.67



Total 3 phase load = AB(single phase load) + 3phase load
= 66.35 + 123.67
= 190.02 amps

DF @ 85 % = 161.517amps

Main breaker will be 200AT/250AF
Now you have the load right - with possibility that maybe you should have used 240 volts, but otherwise correct. Whether demand factor is allowed or not we would need more info on what the loads are. Even without demand factors looks like 200 amps is fine though.
 

topgone

Senior Member
Since you didn't give us the type of 3-phase loads you got there, is it safe to assume these 3-phase loads are all 3-phase motors? The mere mention of 230V will tell people these are motors, IMO. If so, the load amps for each load should be taken from tables per hp ratings of these loads or calculated using the VA/(volts x 1.723xPF), as pointed out by others. Note that motors are inductive loads and will exhibit a PF lower than unity. That said, if these motors are assumed to have a PF of say 0.8 lagging, your line amps will greatly be higher than your calcs.

My calculations tell me you will have 123.63 amps on one line and 184.11 amps on the remaining lines (using PF = 1.0 on all loads). A lower load PF will increase your amperage; say 0.9 PF will make your amps into 137.36 amps, 204.57 amps, and 204.57 amps, respectively.

200AT main will be up its neck then, if above scenario is true.
 

Smart $

Esteemed Member
Location
Ohio
Since you didn't give us the type of 3-phase loads you got there, is it safe to assume these 3-phase loads are all 3-phase motors? The mere mention of 230V will tell people these are motors, IMO. If so, the load amps for each load should be taken from tables per hp ratings of these loads or calculated using the VA/(volts x 1.723xPF), as pointed out by others. Note that motors are inductive loads and will exhibit a PF lower than unity. That said, if these motors are assumed to have a PF of say 0.8 lagging, your line amps will greatly be higher than your calcs.

My calculations tell me you will have 123.63 amps on one line and 184.11 amps on the remaining lines (using PF = 1.0 on all loads). A lower load PF will increase your amperage; say 0.9 PF will make your amps into 137.36 amps, 204.57 amps, and 204.57 amps, respectively.

200AT main will be up its neck then, if above scenario is true.
Prescribed Code calculations are based on VA. The amperes related to wattage (real power) is a lower ampere value than that of VA, not higher.
 

kingpb

Senior Member
Location
SE USA as far as you can go
Occupation
Engineer, Registered
Rockbottom lists location as Manila, Philippines. If that is the location of the work, the standard voltage is 220V single-pole, which means they use 380Y/220V 3ph systems.

Not sure where the 230V is coming from, this needs clarification.
 

Smart $

Esteemed Member
Location
Ohio
Rockbottom lists location as Manila, Philippines. If that is the location of the work, the standard voltage is 220V single-pole, which means they use 380Y/220V 3ph systems.

Not sure where the 230V is coming from, this needs clarification.
Didn't notice location prior. Good catch!

Agree on need for clarification.
 
VA is the original value of equipment,

VA Volts AB BC 3p Pole AT AF
30,20023075.803100150
5,50023013.8232050
9,50023023.8733050
3,3002308.2932050
7502301.8832050
15,26223066.35270100
TOTAL66.35123.67



Total 3 phase load = AB(single phase load) + 3phase load
= 66.35 + 123.67
= 190.02 amps

DF @ 85 % = 161.517amps

Main breaker will be 200AT/250AF

3,300 and 750 are motors, then the 15,262 is the total load of single phase panel board,
single phase panel board is connected to this 3phase panel board, using only the AB wire,

the assignment is to find,
1. the total Amps load of 3 phase panel board,
2. the AT/AF of each branch
3. the AT/AF of main breaker
 

Smart $

Esteemed Member
Location
Ohio
3,300 and 750 are motors, then the 15,262 is the total load of single phase panel board,
single phase panel board is connected to this 3phase panel board, using only the AB wire,

the assignment is to find,
1. the total Amps load of 3 phase panel board,
2. the AT/AF of each branch
3. the AT/AF of main breaker
Short on information we cannot do anything more than guess... some more.

To determine such, we need to know system voltage along with a list of the loads, their type, and power data in watts (possibly with power factor) or volt-amperes, from the nameplate. Article 220 prescribes a method to calculate combined loads. It appears you already know the calculations are in volt-amperes (VA). However, demand factors, continuous loading, and perhaps other considerations may need included, depending on the type of load(s)... and it all contributes to the final (and correct) determination.

The information provided thus far is not enough to make an accurate determination. For example, largest motor is calculated at 125% of its full load current rating. We have no idea whether you have already included the extra 25% or not.
 
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