(31)Transformer Size for Large Motor Starting (10.6.13).xlsx

	B	C	E	F	H	I	J	K
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2						Jignesh.Parmar www.electricalnotes.wordpress.com
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5		:Transformer Detail:			:Transformer Detail:
6		Transformer Size	1000	KVA	Transformer Size		1000	KVA
7		Transformer Secondary Voltage:(v2)	480	Volt	Transformer Secondary Voltage:(v2)		480	Volt
8		% Impedance: (z)	5.75%		% Impedance: (z)		5.75%
9		Allowable Voltage Drop in System:	10%		Allowable Voltage Drop in System:		10%
10		:Motor Detail ( Only One No of Motor):			:Motors Detail ( More Than One No of Motor):
11		Motor Size:	300	Kw	Total KW of Three Phase Motors:		300	Kw
12		Volt (vm): (L-L)	460	Volt	Total KW of Single Phase Motors:		5	Kw
13		Power Factor:	0.8		Volt: (L-L)		460	Volt
14		Motor KVA	240	KVA	Volt: (L-N)		266	Volt
15		Motor Code: (Kva/Hp)			Power Factor:		0.8
16		InRush Current at Starting:(Enter If you know otherwise leave it blank)			Locaked Rotor Current: (Max)		450%
17		Enter Motor Full Load Current(Enter If you know otherwise leave it blank )			Total Three Phase Motors Full Load Current		471	Amp
18		Motor Full Load Current: (ILM)	471	Amp	Total Single Phase Motors Full Load Current		24	Amp
19		Locaked Rotor Current Multiplier: (Min)	4.10		Total Motors Full Load Current		494	Amp
20		Locaked Rotor Current Multiplier: (Max)	4.50		Motor InRush KVA At Starting		1772	KVA
21		Locaked Rotor Current (L1): (Min)	1930	Amp
22		Locaked Rotor Current (L2): (Max)	2118	Amp
23		Motor InRush KVA At Starting: (IrsM)	1688	KVA
24		How many times Motor Starts per Hours	2
25		:Calculations:			:Calculations:
26		Full Load Current of Transformer : (ILX)	1203	Amp	Full Load Current of Transformer : (IL)		1203	Amp
27		Short Circuit Current at Transformer Secondary: (Isc)	20919	Amp	Short Circuit Current at Transformer Secondary: (Isc)		20919	Amp
28		Max KVA of Transformer at Isc: Q1	17391	KVA	Max KVA of Transformer at Isc		17391	KVA
29		Motor InRush KVA At Starting:(IrsM)	1688	KVA	Motor InRush KVA At Starting		1772	KVA
30		Voltage Drop at Transformer Secondary Due to Motor inRush: (Vd)	10%	90%	Voltage Drop at Transformer Secondary Due to Motor inRush		10.2%	90%
31		Transformer Secondary Voltage	433	Volt	Transformer Secondary Voltage		431	Volt
32		:Result:			:Result:
33		(1) Motor Full Load Current <= 65% Transformer Full Load Current	Yes		(1) Motor Full Load Current <= 65% Transformer Full Load Current		Yes
34		(2) Voltage Drop at Transformer Secondary Due to Motor inRush	Low		(2) Voltage Drop at Transformer Secondary Due to Motor inRush		High
35		(3) Transformer Size:(20% Added due to motor starts more than once/Hour)	1200	Kva	(3) Transformer Size:		1000	KVA
36		Size of Transformer is Adequate			Increase Size of Transformer
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39		Calculation Formulas:
40		ILX=KVA/(1.732xv2)
41		ILM=(Kwx1000)/(1.732xVmxP.F)
42		Isc=ILx/z
43		Q1=(v2xISCxILMx1.732)/1000
44		IrsM=(VmxL2x1.732)/1000
45		Vd=IrsM/Q1
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49		Code Letter (KVA per HP) -Locked Rotor Current
50		Motor Code	Min	Max
51	1	A	3.15
52	2	B	3.16	3.55
53	3	C	3.56	4
54	4	D	4.1	4.5
55	5	E	4.6	5
56	6	F	5.1	5.6
57	7	G	5.7	6.3
58	8	H	6.4	7.1
59	9	J	7.2	8
60	10	K	8.1	9
61	11	L	9.1	10
62	12	M	10.1	11.2
63	13	N	11.3	12.5
64	14	P	12.6	14
65	15	R	14.1	16
66	16	S	16.1	18
67	17	T	18.1	20
68	18	U	20.1	22.4
69	19	V	22.5
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74		4.1
75		4.5
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