Alpha Technologies Spectra Series - Manual (Page 19)

Preliminary Operating Instructions 19 of 62 AIP SERVICE NUMBER 1-800-863-3364
7. DC OUTPUT
It is recommended that a DC disconnect switch or circuit breaker be used between the charger and the DC
bus. This device should have lockout capability to allow the charger to be disconnected from the DC bus when
connecting the charger during installation and maintenance.
7.1 DC OUTPUT CONNECTIONS
The standard charger is shipped with conduit knockouts and no DC output cable. Determine which
charger knockout to route the DC output cable through. See Section 6.3. Make sure to keep the DC
output cable isolated from the AC input cables and any other optional wiring.
To help in determining the proper size of cable to use for the DC output, FIGURE 7.1 lists the DC voltage
drop per one foot (305mm) of cable for the various Rated DC currents of the chargers and various wire
sizes. Take the appropriate number from FIGURE 7.1, and multiply it by the cable length needed to get
the approximate voltage drop from the charger to the battery or DC bus. FIGURE 7.1 values are
approximate values, the exact value can be measured after installation.
NOTE: If the total voltage drop of the DC output cable is greater than 1% of the charger voltage ( 0.24
VDC for a 24 VDC system, 0.48 VDC for a 48 VDC system, 1.3 VDC for a 130 VDC system) it is
recommended that the optional Remote DC Voltage Sensing cable be used.
To connect the DC output cable, route the conduit through the appropriate knockout hole. Route the DC
positive wire to terminal lug labeled DC POSITIVE and the DC negative wire to terminal lug labeled DC
NEGATIVE located above the DC breaker as shown in FIGURE 6.1-2. For proper connection, torque
the terminal strip screws to 18 inch pounds (2Nm). The charger will not operate in a reversed polarity
condition. The DC output circuit breaker is used to protect the silicon-controlled rectifiers (SCRs).
NOTE: DC circuit breaker may trip when switched on until capacitors are charged.
FIGURE 7.1: VOLTAGE DROP PER 1 FT (305mm) OF WIRE TABLE
For stranded copper wire at 68°F (20°C)
RATED DC CURRENT, AMPERES
WIRE
SIZE
(AWG.) 6A 12A 18A 20A 25A 50A
16 0.0450 0.0900 0.1440 - - -
14 0.0270 0.0540 0.0864 0.0945 - -
12 0.0180 0.0360 0.0576 0.0630 0.0720 -
10 0.0110 0.0220 0.0352 0.0385 0.0440 0.0880
8 0.0070 0.0140 0.0224 0.0245 0.0280 0.0560
6 0.0045 0.0090 0.0144 0.0158 0.0180 0.0360
4 0.0025 0.0050 0.0080 0.0088 0.0100 0.0200
2 0.0018 0.0036 0.0058 0.0063 0.0072 0.0144
1 0.0015 0.0030 0.0048 0.0053 0.0060 0.0120
0 0.0011 0.0022 0.0035 0.0039 0.0044 0.0088
8. REMOTE AND ALARM I/O RELAY OPTIONS
The Remote option allows the charger to be controlled and monitored remotely. The ALARM I/O relay board
allows the user to connect other devices to it to monitor various faults. The following sections go over function
and installation of these optional parts.
8.1 REMOTE DC VOLTAGE SENSING
This option will compensate for the voltage drop across the DC output cable due to the resistance and
current flowing through it. The remote voltage sensing cable can measure the DC voltage of batteries or
DC bus up to 30 ft. (9m) with the standard cable length. This can be extended with a longer cable. This
gives the charger display a more accurate voltage display. In order for the charger to function, the
connection to the DC bus must be secure and reliable.