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Electrical question- power consumed calculation.
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20-09-2012 10:50pm#1Maybe one of you lads can help me with this.
Three 12.5 ohm heating elements are connected in an industrial oven in a delta configuration to a 115/200V 3 phase supply.
Determine:
a. the current carried by the supply cables?
b. total power consumed?
My brain's not functioning at the moment.
We're all in this psy-op together.🤨
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Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭
Join Date:Posts: 12291
Maybe one of you lads can help me with this.
Three 12.5 ohm heating elements are connected in an industrial oven in a delta configuration to a 115/200V 3 phase supply.
Determine:
a. the current carried by the supply cables?
b. total power consumed?
My brain's not functioning at the moment.
Let the phase current (current passing through 1 element) = Iph
Let the phase voltage = Vph
Let the phase impedance = Zph
Let the line current = In (this is the current carried by the supply cables)
Let the line voltage = Vn
⇒ Iph = Vph/Zph
In this case the impedance = the resistance
As the load is connected in delta configuration the phase voltage = the line voltage.
⇒ Iph = 200/12.5 = 16A
In = √3 x Iph
In = √3 x 16 = 27.71A
Therefore the current carried by the supply cables is 27.71A
As this is a resistive load Cosɵ = 1
Power for a 3 phase load = √3 x Vn x In x Cosɵ
⇒ Total power consumed = √3 x 200 x 27.71 x 1 = 9600 Watts = 9.6kW0 -
Let the phase current (current passing through 1 element) = Iph
Let the phase voltage = Vph
Let the phase impedance = Zph
Let the line current = In (this is the current carried by the supply cables)
Let the line voltage = Vn
⇒ Iph = Vph/Zph
In this case the impedance = the resistance
As the load is connected in delta configuration the phase voltage = the line voltage.
⇒ Iph = 200/12.5 = 16A
In = √3 x Iph
In = √3 x 16 = 27.71A
Therefore the current carried by the supply cables is 27.71A
As this is a resistive load Cosɵ = 1
Power for a 3 phase load = √3 x Vn x In x Cosɵ
⇒ Total power consumed = √3 x 200 x 27.71 x 1 = 9600 Watts = 9.6kW
That's great. thanks for that.
We're all in this psy-op together.🤨
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No problem.
Does it make sense to you ?
Yep, it does, cheers.
It's coming back to me now.:)
In star:
I line = I phase
V line = √3 x V phase.
and the opposite in delta.
And a p.f of unity (1) due it being a purely resistive load.
So if it was connected in star (with 380V/220V 3 ph. supply) and three 44 ohm elements:
Iph= Vph/Rph= 220/44= 5A.
Total power consumed:
P= √3 x 380 x 5 x 1= 3.3 KW.
Am I correct? We're all in this psy-op together.🤨
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Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭ Join Date:Posts: 12291
If the resistance is 44 ohms, then yes the above is correct.Yep, it does, cheers.
It's coming back to me now.:)
In star:
I line = I phase
V line = √3 x V phase.
and the opposite in delta.
And a p.f of unity (1) due it being a purely resistive load.
So if it was connected in star (with 380V/220V 3 ph. supply) it would be:
Iph= Vph/Rph= 220/44= 5A.
Total power consumed:
P= √3 x 380 x 5 x 1= 3.3 KW.
Am I correct?0 -
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Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭ Join Date:Posts: 12291
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I've one more question. Maybe somebody can help.
In a similar circuit with just one stop and one start the contact numbers would be 1 & 2 for the stop and 3 & 4 for the start and 95 & 96 for the thermal overload.
Anyone know what the contact numbers should be on the stops and starts on a duel stop start circuit?We're all in this psy-op together.🤨
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I've one more question. Maybe somebody can help.
In a similar circuit with just one stop and one start the contact numbers would be 1 & 2 for the stop and 3 & 4 for the start and 95 & 96 for the thermal overload.
Anyone know what the contact numbers should be on the stops and starts on a duel stop start circuit?
It would be still 1 & 2 for both stops (connected in series) and 3 & 4 for both starts (connected in parallel). Each button would be labeled X1, X2, X3 and X4 or whatever you want. The O/L is still 95 & 96 but only one would be used.0 -
It would be still 1 & 2 for both stops (connected in series) and 3 & 4 for both starts (connected in parallel). Each button would be labeled X1, X2, X3 and X4 or whatever you want. The O/L is still 95 & 96 but only one would be used.
Thanks for that. Just what I thought. We're all in this psy-op together.🤨
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Can't see anything wrong with that. The way I drew it is the way I learned it during my training. Although mine is just for one direction on the motor, you get the idea. Same thing reallyThe one I'm thinking of is similar to this, but with the t.o/l just after the stop button in the circuit.
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