Calculate Size of Diesel Generator
November 2, 2015 38 Comments
Calculate Size of Diesel Generator having following Electrical Load. Consider Future Expansion ratio is 10%. Average use of Equipment is 0.8 (1 is Full Time Use)
- 4 No’s of 1Ph, 230V, 80Watt CFL Bulbs, Diversity Factor is 0.8; Starting & Running P.F is 0.8.
- 2 No’s of 1Ph, 230V, 3000Watt Air Condition, Diversity Factor is 1, Starting & Running P.F is 0.8.
- 2 No’s of 1Ph, 230V, 500Watt Halogen Lights Diversity Factor is 0.8 Starting & Running P.F is 0.8.
- 1 No’s of 1Ph,230V, 10KW Motor with Y-D Starter, Diversity Factor is 0.8,Starting P.F is 0.7 & Running P.F is 0.8
- 1 No’s of 3Ph,430V, 130KW Motor with Soft Starter , Diversity Factor is 0.8,Starting P.F is 0.7 & Running P.F is 0.8
Calculation:
| Type of Load | Equipment | Starting Current |
| Linear Load | General Equipment |
100% of Full Load Current |
| Non-Linear Load | UPS, Inverter, Computer, Ballast | 160% of Full Load Current |
| Type of Starter | Starting Current |
| DOL | 6 X Full Load Current |
| Star-Delta | 4 X Full Load Current |
| Auto Transformer | 3 X Full Load Current |
| Soft Starter | 2 X Full Load Current |
| VFD | 1.5 X Full Load Current |
Load Calculation-1:
- Full Load KW of CFL Bulb=(No X Watt X Diversity Factor) /1000
- Full Load KW of CFL Bulb=(4x80x0.8)/1000=0.3KW
- Full Load KVA of CFL Bulb=KW / P.F
- Full Load KVA of CFL Bulb=0.3 / 0.8=0.4KVA————(H)
- Full Load current of CFL Bulb=(No X Watt X Diversity Factor) / (Volt x P.F)
- Full Load current of CFL Bulb=(4x80x0.8) / (230×0.8) =2 Amp—-(M)
- Type of Load=Linear
- Starting KVA of CFL Bulb=1 X (KW / Starting P.F)
- Starting KVA of CFL Bulb=0.3 / 0.8=0.4KVA———————-(1)
- Starting Current=100% of Full Load Current.
- Starting Current=1 X 2= 2 Amp.————–(A)
Load Calculation-2:
- Total Full Load KW of A.C=(No X Watt X Diversity Factor) /1000
- Total Full Load KW of A.C =(2x3000x0.8)/1000=4.8KW
- Total Full Load KVA of A.C =KW / P.F
- Total Full Load KVA of A.C =4.8 / 0.8=6KVA————(I)
- Total Full Load current of A.C =(No X Watt X Diversity Factor) / (Volt x P.F)
- Total Full Load current of A.C =(2x3000x0.8) / (230×0.8) =26 Amp——-(N)
- Type of Load=Non Linear
- Starting KVA of A.C=1.6 X (KW / Starting P.F)
- Starting KVA of A.C =1.6 X (4.8 / 0.8)=9.6KVA———————-(2)
- Starting Current=160% of Full Load Current.
- Starting Current=1.6 X 26= 42 Amp. ————–(B)
Load Calculation-3:
- Full Load KW of Halogen Bulb=(No X Watt X Diversity Factor) /1000
- Full Load KW of Halogen Bulb=(2x500x0.8)/1000=0.8KW
- Full Load KVA of Halogen Bulb=KW / P.F
- Full Load KVA of Halogen Bulb=0.8 / 0.8=1KVA————(J)
- Full Load current of Halogen Bulb=(No X Watt X Diversity Factor) / (Volt x P.F)
- Full Load current of Halogen Bulb=(2x500x0.8) / (230×0.8) =4 Amp—-(O)
- Type of Load=Non Linear
- Starting KVA of Halogen Bulb =1.6 X (KW / Starting P.F) / Starting P.F
- Starting KVA of Halogen Bulb =1.6 X (0.8 / 0.8)=1.6KVA———————-(3)
- Starting Current=160% of Full Load Current.
- Starting Current=1.6 X 4= 7 Amp .————–(C)
Load Calculation-4:
- Full Load KW of Motor=(No X Watt X Diversity Factor) /1000
- Full Load KW of Motor =(1x10000x0.8)/1000=8KW
- Full Load KVA of Motor =KW / P.F
- Full Load KVA of Motor =8 / 0.8=10KVA————(K)
- Full Load current of Motor =(No X Watt X Diversity Factor) / (Volt x P.F)
- Full Load current of Motor =(1x10000x0.8) / (230×0.8) =43 Amp—-(P)
- Type of Starter=Star-Delta
- Starting KVA of Motor =4 X (KW / Starting P.F)
- Starting KVA of Motor=4X (8 / 0.7)=45.7KVA————————(4)
- Starting Current=4 X Full Load Current
- Starting Current=4 X 11.4 = 174 Amp.————–(D)
Load Calculation-5:
- Full Load KW of Motor=(No X Watt X Diversity Factor) /1000
- Full Load KW of Motor =(1x120000x0.8)/1000=96KW
- Full Load KVA of Motor =KW / P.F
- Full Load KVA of Motor =96 / 0.8=120KVA————(L)
- Full Load current of Motor =(No X Watt X Diversity Factor) / (Volt x P.F)
- Full Load current of Motor =(1x120000x0.8) / (1.732x430x0.8) =167 Amp—-(Q)
- Type of Starter=Auto Transformer
- Starting KVA of Motor =3 X (KW / Starting P.F)
- Starting KVA of Motor=3 X (96 / 0.7)=411.4KVA—————(5)
- Starting Current=3 X Full Load Current
- Starting Current=3 X 167 = 501 Amp.————–(E)
Total Load Calculation:
- Total Starting KVA = (1) + (2) +(3) + (4) + (5)
- Total Starting KVA =0.4+9.6+1.6+45.7+411.4 =468.7 KVA
- Total Starting Current = (A) + (B) +(C) + (D) + E
- Total Starting Current =2+42+7+174+501= 725 Amp
- Total Running KVA =(H)+(I)+(J)+(K)+(L)
- Total Running KVA =4+6+1+10+120= 137KVA
- Total Running Current=(M)+(N)+(O)+(P)+(Q)
- Total Running Current=2+26+4+43+167= 242 Amp
- Size of Diesel Generator= Starting KVA X Future Expansion X Average Use of Equipments
- Size of Diesel Generator=468.7 X 1.1 X 0.8
- Size of Diesel Generator= 412 KVA
Summary:
- Total Starting KVA =468.7 KVA
- Total Starting Current =725 Amp
- Total Running KVA = 137KVA
- Total Running Current= 242 Amp
- Size of Diesel Generator= 412 KVA
JIGNESH PARMAR
Dear sir,
Thanks for your valuable Generator calculation tips and your advice ,but now i need the calculation of lighting power density, please send to me on the below mail ID ,
Sir,
Thanks , this is very useful for step 5 tpm pasing stages .
As all the associates along with officer should know how to calculate .
All your mails are very useful to us .i want to share with you one product called Ultra .
We took trials and our team saying there is no power saving I can share the details .
Regards
SANjeev
Sr manager
Mahindra
91 9922900891
Dear jignesh sir,
i want to know some doubts about electrical system,
1.why powerfactor defined by “cos phi” not tan and sin?
2.why we are goes to higher voltage to step down 433v…11kv to 433?
Following points may be noticed 1) PF should be considered as 0.95 as we normally use APFC but don’t consider it for calculation of capacity of DG and Substation. 2)Loading for Motors is taken as 100% which never designed for. Get some cases studies only then we may know. I have done study for three buildings where Substation capacities were 3 to 4 times than peak due to which not only huge initial investment but very high maintenance cost also.
dear sir pls ans me calculation in transformer load
wery nice and easy calculation method thanks
thank u very much sir
mahesh
Sir may I want to know that single phase supply 230 v,8kw motor with star delta starter available. Or ??
Dear Sir,
Is it possible to have star /delta starter for 1 Ph motor?
Regards
Kuldip Singh
Sir
Sent from Yahoo Mail on Android
Nice presentation.
Could you please tell me why the starting kVAs of all the loads in the example have been added to arrive at the genset capacity? Does this approach not imply that all the loads are being simultaneously started up? If this is not intended, then will we not land up with an oversized generator?
On the other hand if all the loads are not proposed to be started up simultaneously, then I think the right approach would be to add up the running kVAs of all the loads except that of the biggest load (130 kW motor or is it 120 kW as it appears in the calculation ?) which would be 17 kVA and then to this fig add the starting kVA of the biggest load which would be 411.4 kVA. This would give us a genset capacity of 428.4 kVA.
Thanks
800 kva DG is their…….? i want how much current it takes?
800kva DG how much current it takes?
Hello Sir,
This article is very useful for me,but how do you say CFL lamp is linear load?
that is very important.
thanks
very useful
thanks
Dear sir,
how do i calculate DG capacity requirement to 2000 TR centrifugal chiller
sir starting kva is 468 and generator size is only 412 kva ………..how can gen. bear this much load
Dear Sir,
I have 90 KW motor with Star Delta Starter. 200 A MCCB (Schneider NSX200 is tripping. What is the correct size of MCCB to be used ??
GOOD,BUT I HAVE SOME DOUBTS.YOU DIDNOT CONSIDER THE STARTING SEQUENCE OF MOTOR AND ALREADY DIVERSITY FACTOR IS CONSIDERED AND AT THE END YOU AGAIN MULTIPLIED BY THE AVERAGE USE OF EQUIPMENTS.
Hello sir
The future expansion ratio is 10percent of what.
In the final calculation, you used 1.1 as the future expansion ratio. Can you help in explaining how you got that
Sir,
Diversity factor is taken 0.8. But in Demand Factor-Diversity Factor-Utilization Factor-Load Factor OCTOBER 31, 2011 blog, it shows that diversity factor is always greater than 1. So in this article is it Demand factor???
Reg.
Bhavesh Dabhoya
dear sir,
please give calculation for transformer loads..
Why we are considering pf 0.8 when selecting DG size ??
Whereas for Transformer sizing we are considering pf as per catalogue of Motor.
Hello sir.your article has been wonderful.I have been reading since 2011.You have really impacted someone here in Nigeria.I just have a question.In your article,i read diversity factor is always greater than one,but here its less than one.In also the article for calculating branch ELCB/MCB/MCCB,you used Demand factor of less than one.Pls sir,i want to know when to apply Demand factor and Diversity factor.
how to calculate Generation by DG(KVAH)
Thanks calculation intresting
What will be the size of D.G. set in case three motors of 100 KW each are to be started one after another?
My load is 5600 kw how are use kva in dg set
Please send me electrical calculation pdf on my email
Hi Sir, You have already considered Diversity Factor on all individual loads , there is no need to consider it again while calculating the size of DG. Please look into that.
Sir if we have single phase load of 75 Amp ground floor, 80 Amp 1st. floor, 70 amp 2nd floor, i want to install 3-phase DG set as stand by , what will be size of dg set in kva. from:- Rakesh Kumar Sharma M:- 9418031806. pl send reply at the earliest, thanks.
Dear Jignesh,
VFD driven equipment do not always starts at 1.5 times the running load. VFDs are flexible and can be programmed to start in a particular way. E.g. A It is possible to program an industrial extractor fan to starts as a ramp such that it takes just increasing current over to short period of time till it reaches the rated speed-in which case the current taken never exceeds the 110% regular full load running amps.
Why we use Avg use of Equipment
Nice explanation, thanks a lot
Very informative article! I love how you provided complete details for gas generators. Keep writing great articles like this one. Thanks a lot!
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