Choosing Power Supply Wires for Elmo's PCB mounting Servo Drives-Whistle, Bell & Guitar: Application Note

Always use suitable AWG gauge wires. It is highly recommended to use thicker wires in order to reduce bus impedances, voltage drops and interferences. For reference please use the following table:

AWG gauge	Conductor Diameter Inches	Conductor Diameter mm	Ohms per 1000 ft.	Ohms per km	Maximum amps for chassis wiring
AWG gauge	Conductor Diameter Inches	Conductor Diameter mm	Ohms per 1000 ft.	Ohms per km	Maximum amps for chassis wiring
0	0.3249	8.25246	0.0983	0.322424	245
1	0.2893	7.34822	0.1239	0.406392	211
2	0.2576	6.54304	0.1563	0.512664	181
3	0.2294	5.82676	0.197	0.64616	158
4	0.2043	5.18922	0.2485	0.81508	135
5	0.1819	4.62026	0.3133	1.027624	118
6	0.162	4.1148	0.3951	1.295928	101
7	0.1443	3.66522	0.4982	1.634096	89
8	0.1285	3.2639	0.6282	2.060496	73
9	0.1144	2.90576	0.7921	2.598088	64
10	0.1019	2.58826	0.9989	3.276392	55
11	0.0907	2.30378	1.26	4.1328	47
12	0.0808	2.05232	1.588	5.20864	41
13	0.072	1.8288	2.003	6.56984	35
14	0.0641	1.62814	2.525	8.282	32
15	0.0571	1.45034	3.184	10.44352	28
16	0.0508	1.29032	4.016	13.17248	22
17	0.0453	1.15062	5.064	16.60992	19
18	0.0403	1.02362	6.385	20.9428	16
19	0.0359	0.91186	8.051	26.40728	14
20	0.032	0.8128	10.15	33.292	11
21	0.0285	0.7239	12.8	41.984	9
22	0.0254	0.64516	16.14	52.9392	7
23	0.0226	0.57404	20.36	66.7808	4.7
24	0.0201	0.51054	25.67	84.1976	3.5
25	0.0179	0.45466	32.37	106.1736	2.7
26	0.0159	0.40386	40.81	133.8568	2.2
27	0.0142	0.36068	51.47	168.8216	1.7
28	0.0126	0.32004	64.9	212.872	1.4
29	0.0113	0.28702	81.83	268.4024	1.2
30	0.01	0.254	103.2	338.496	0.86
31	0.0089	0.22606	130.1	426.728	0.7
32	0.008	0.2032	164.1	538.248	0.53

Table 1: AWG gauge wires vs. current carrying capacity

For drives that are up to 10 A cont/20 A peak, the internal capacitance is always sufficient and adequate.
For wires up to 1.5 – 2 meters long (the actual length depends on the size of the wires), the internal capacitance of the 15 A cont/ 30 A peak and 20 A cont/40 A peak drives is always sufficient.
For drives that are higher than 10 A cont/20 A peakwith wires that are longer than 1.5 – 2 meters, additional capacitance must be added to the DC power bus as follows:

PCB Mounting and the Electrolytic capacitor. In most of the applications an electrolytic capacitance greater than 100 µF is sufficient. The electrolytic capacitors should be high current ripple capacitors.
PCB mounting and Ceramic Capacitors. If a dedicated PCB has been designed, it is recommended to add ceramic capacitance on the DC power bus. Using ceramic capacitors saves space and provides the best high frequency performance. A sufficient capacitance is greater than 30 µF. The best way to achieve this capacitance is by connecting a few ceramic capacitors in parallel.
PCB Mounting and Combination Electrolytic and Ceramic Capacitors. A more reasonable design approach is a combination of ceramic capacitance of a few microFaradays (1 µF – 10 µF) and an electrolytic capacitance greater than 100 µF. The electrolytic capacitors should be high current ripple capacitors.
Solo Wiring. For Solo applications, an electrolytic capacitor greater than 100 µF must be connected to the DC power wires at a distance that is less than 1.5 – 2 meters from the Solo. The electrolytic capacitors should be high current ripple capacitors.

Application Notes