ANSI/CTA-2015:2007 pdf download.Mobile Electronics Cabling Standard.
4 Power Handling Capability
The power handbng capability of any cable is dependent on the malenal used to make the cable, and the size of the cable. The lower the resistivity of the conductive material used in the cable, the more power it can handle, all else being equal. Also, the larger the cross-sectional area of the cable the more power It can handle, all else being equal. CEA-201 5 rates power cables and speaker cables fferently.
4.1 Power Cables
Power cables are rated in terms of the amplifiers with which they should be used. When amplifier power is measured in accordance with CEA-2006-A the amplifier power that Is reported 10 consumers for a particular product is not equivalent to the power consumed by that product. Instead, it represents the power delivered to 4 ohm speakers. In order to convert this number to power consumed by the amplifier one needs to factor in the efficiency of the amplifier. For example, it an amplifier is rated as a 50 wall per channel x 2 channel amplifier using CEA-2006-A, and the efficiency of the amplifier Is 50 percent, then only 50 percent of the power supplied to the amplifier makes it to the speakers, and the total power consumed by the amplifier is 200 watts (50 watts per channel x 2 channels divided by 0.5). So, in order to supply power to the CEA-2006-A-tated amplifier in this example, the power cables must be able to handle 200 watts of power.
CEA•201 5 assumes a standard efficiency of 50 percent for all amplifiers, which is typical performance for a class AB amplifier. While some amplifiers may be more efficient than this, it Is believed that a 50 percent efficiency assumption for all amplifiers will ensure that the CE#201 S-rated capacity of power cables will be equal to or greater than the power consumption of amplifiers It their output power Is rated In accordance with CEA-2006-A.
Once the amount of power that needs to be delivered to the amplifier by the cable is known the next step is to determine the current flowing through the cable. Current equals power divided by voltage. We know the power, and we also know that the voltage supplied to the amplifier is coming from a car battery. For CEA•201 5 purposes it is assumed that the car battery is supplying 14.4 V DC, and that there is a 0.25 V DC drop in the cable supplying power to the amplifier. With these assumptions the current flowing through the cable is:
(CEA -2006-A rated total amplifier power in watts) x 2
current in cable –
14.4 battery volts – 0.25 volts dropped in cable
The x 2 in the above equation is a result of the assumption that only 50 percent of the power consumed by the amplifier makes It to the speakers. Once the amount of current in the cable that corresponds to the assumed 0.25 V drop in the cable is known, the resistance in the cable can be calculated. The resistance in the cable in ohms is equal to the voltage drop in the cable in volts (assumed to be 0.25 V) divided by the current in the cable In amperes. Substituting the above formula for calculating the current into this equation results in a formula that determines cable resistance as a function of the battery voltage, the voltage dropped in the cable, and the CEA-2006-A rated power of the amplifier, as follows:
0.25 V x (14.4 battery volts -0.25 volts dropped in cable) resistance of cable =
(CEA – 2006 – A rated total amplifier power in watts) x 2
In other words, using the CEA-201 5 assumptIons about amplifier power and voltage drop in the power cable, the maximum amount of resistance that the power cable can have is.
