Switchboard and MCC Volt Drop Tables

Distribution Switchboard Volt Drop Tables

Calculations to give the maximum sizes of motor outputs that may be connected to distribution switchboards for the major starting methods where the motor full load currents are calculated for a motor with an efficiency of 90% and a power factor of 0.85 at various calculated switchboard fault levels for a maximum of a 1% volt drop are shown in the following tables:-

Table 2 – 11kV max load application

11kV Distribution Switchboard Load Application for max 1% Volt Drop
Actual Fault Level kA	Max Current Amps	Direct on Line kW 7xFLC	Star delta kW 2.5xFLC	Auto Transformer kW 1.75xFLC	Rotor Resistance kW 1.5xFLC
25	250	520	1457	2082	2429
21	210	437	1224	1749	2040
16	160	333	932	1332	1554
13.1	131	272	763	1091	1272
10	100	208	583	832	971
5	50	104	291	416	485

Table 3 – 3.3kV max load application

3.3kV Distribution Switchboard Load Application for max 1% Volt Drop
Actual Fault Level kA	Max Current Amps	Direct on Line kW 7xFLC	Star delta kW 2.5xFLC	Auto Transformer kW 1.75xFLC	Rotor Resistance kW 1.5xFLC
21	210	131	367	524	612
16	160	99	279	399	466
13.1	131	81	229	327	381
10	100	62	174	249	291
5	50	31	87	124	145
2.5	25	15	43	62	72
1	10	6	17	24	29

Table 4 – 400V max load application

400V Distribution Switchboard Load Application for max 1% Volt Drop
Actual Fault Level kA	Max Current Amps	Direct on Line kW 7xFLC	Star delta kW 2.5xFLC	Auto Transformer kW 1.75xFLC	Rotor Resistance kW 1.5xFLC
120	1200	90	254	363	424
115	1150	87	243	348	406
110	1100	83	233	333	388
105	1050	79	222	318	371
100	1000	75	212	302	353
95	950	71	201	287	335
90	900	68	190	272	318
85	850	64	180	257	300
80	800	60	169	242	282
75	750	56	159	227	265
70	700	53	148	212	247
65	650	49	137	196	229
60	600	45	127	181	212
55	550	41	116	166	194
50	500	37	106	151	176
45	450	34	95	136	159
40	400	30	84	121	141
35	350	26	74	106	123
30	300	22	63	90	106
25	250	18	53	75	88
20	200	15	42	60	70
15	150	11	31	45	53
10	100	7	21	30	35
5	50	3	10	15	17

Motor Control Centre Volt Drop Tables

Calculations to give the maximum sizes of motor outputs that may be connected to motor control centres for the major starting methods where the motor full load currents are calculated for a motor with an efficiency of 90% and a power factor of 0.85 at various calculated switchboard fault levels for a maximum of a 3% volt drop are shown in:-

Table 5 – 3.3kV max load application

3.3kV Distribution Switchboard Load Application for max 3% Volt Drop
Actual Fault Level kA	Max Current Amps	Direct on Line kW 7xFLC	Star delta kW 2.5xFLC	Auto Transformer kW 1.75xFLC	Rotor Resistance kW 1.5xFLC
21	630	393	1101	1574	1836
16	480	299	839	1199	1399
13.1	393	245	687	981	1145
10	300	187	524	749	874
5	150	93	262	374	437
2.5	75	46	131	187	218
1	30	18	52	74	87

Table 6 – 400V max load application

400V Distribution Switchboard Load Application for max 3% Volt Drop
Actual Fault Level kA	Max Current Amps	Direct on Line kW 7xFLC	Star delta kW 2.5xFLC	Auto Transformer kW 1.75xFLC	Rotor Resistance kW 1.5xFLC
120	3600	272	763	1090	1272
115	3450	261	731	1044	1219
110	3300	249	699	999	1166
105	3150	238	667	954	1113
100	3000	227	636	908	1060
95	2850	215	604	863	1007
90	2700	204	572	817	954
85	2550	193	540	772	901
80	2400	181	508	726	848
75	2250	170	477	681	795
70	2100	159	445	636	742
65	1950	147	413	590	689
60	1800	136	381	545	636
55	1650	124	349	499	583
50	1500	113	318	454	530
45	1350	102	286	408	477
40	1200	90	254	363	424
35	1050	79	222	318	371
30	900	68	190	272	318
25	750	56	159	227	265
20	600	45	127	181	212
15	450	34	95	136	159
10	300	22	63	90	106
5	150	11	31	45	53