Alpha Technologies CXPS 48-1.2-225 48 Vdc - Manual (Page 28)

053-691-B1 Rev E Page 20 of 33
5.4 Calculating output wire size requirements
To calculate wire sizes, first determine the appropriate maximum voltage drop requirement. Use the formula
below to calculate the CMA wire size requirement. Determine the size and number of conductors needed to
satisfy the CMA requirement.
CMA = (A x LF x K) / AVD, where:
CMA = Cross section of wire in circular MIL area
A = Ultimate drain in amps
LF = Conductor loop feet
K = 11.1 constant factor for commercial (TW type) copper wire
AVD = Allowable voltage drop
Check again that the ampacity rating of the cable meets the requirement for the installation application. Consult
local electrical codes (NEC, CEC, etc.) for guidelines. If required, increase the size of the cable to conform to the
code.
5.5 DC output connections
WARNING: Leave the cables or bus bars disconnected at the battery and verify the output polarity
using a voltmeter. Make the battery connections only after all other wiring is complete.
DC output wire must be UL approved XHHW or RHH/RHW (RW90 type for Canadian users). Control and sense
wires must be UL approved Style 1015 (TEW type for Canadian users).
Terminate the cable leads with appropriate crimp lugs.
Secure the positive and negative DC output cables to the shelf output post of the correct polarity; i.e., +Vcable to
+Vpost. Ensure that the washers are placed on the bolts in the same order in that they were shipped from the
factory.
Connect the common output leg of the rectifier system to the ground. This is typically done at the load common
termination point.
5.6 System and battery connections
WARNING: Ensure that the correct polarity is used for all cable terminations.
Refer to guidelines supplied with the load equipment. Distribution cables are typically sized to provide a 0.5 V loop
drop at full load and to meet ampacity requirements of the protection fuse or circuit breaker.
Size the battery cables for a 0.25 V drop from the battery to the power system at full load, including anticipated
additional loads. The cables must also meet ampacity requirements. Cables terminating directly on battery posts
or connection details must be secured so that there is no stress on the battery posts. To reduce corrosion, use
lead plated lugs and lead plated or stainless steel hardware on all terminations of vented batteries.
Prepare, route, and connect cables from the power system to the battery termination points. Burnish the
terminating points and apply a corrosion-inhibiting agent, such as NO-OX-ID, to all battery terminal connections.
Do not make the final connections to the live batteries. Switch off the battery contactors or remove the battery
fuses. See system startup procedure before connecting batteries online.