Product Manual

42
DIVERSION CHARGE CONTROL
43
MORNINGSTAR CORPORATION
6.0
draw. This peak load current must not exceed the TriStar’s rating.
NOTE: Because the battery can supply any size load, the peak load current is not
limited by the source (hydro or wind rating). The diversion load’s power rating is the
critical specification for reliable battery charging.
REMARQUE : La batterie pouvant fournir une charge de n’importe quelle
dimension, le pic d’intensité de la charge n’est pas limité par la source (puissance
hydro ou éolienne). La puissance nominale de la charge de diversion constitue la
spécification critique pour une charge fiable de la batterie.
6.4.3 Load Power Ratings
The power rating of the diversion load will depend on the voltage of the battery
being charged. If the heating element is not rated for the same voltage as the
diversion system, the power rating of the load must be adjusted to the diversion
system’s voltage.
The manufacturers typically rate the heating elements for power at a
specified voltage. The peak load current at the load’s rated voltage will
be the power divided by the rated voltage (I = P / V). For example:
2000W / 120V = 16.7 amps of current.
If the load is being used at a voltage less than the load’s rated voltage,
the power can be calculated by the ratio of the voltages squared. For
example, a 120 volt 1000 watt heating element being used at 60 volts:
1000W x (60/120)
2
= 250 watts
The 1000W element will only dissipate 250W when being used at 60 volts.
NOTE: The loads (heating elements) can be used at the manufacturer’s voltage
rating, or at a lower voltage. Do not use the load at a higher voltage than the load’s
rating.
REMARQUE : Les charges (éléments de chauffe) peuvent être utilisées à la tension
nominale du fabricant ou à une tension inférieure. N’utilisez pas la charge à une
tension supérieure à la tension nominale.
6.4.4 Maximum Diversion Load
The diversion load should never exceed the TriStar’s current rating (45A or 60A).
Note that the load is not limited by the source (wind, hydro), and will draw its rated
current from the battery.
The following table specifies the absolute maximum diversion loads that can
be used with each TriStar version. These loads (heating elements) are rated
for the same voltage as the system voltage.
Nominal Voltage TriStar-45 TriStar-60
48V 2700W at 60V 3600W at 60V
24V 1350W at 30V 1800W at 30V
12V 675W at 15V 900W at 15V
These maximum power ratings are translated to the equivalent at 120 volts in
the following table. If using heating elements rated for 120 volts, the power
ratings of all the elements can be simply added up and the sum compared
with this table and no further math is required.
Nominal Voltage TriStar-45 TriStar-60
48V 10,800W at 120V 14,400W at 120V
24V 21,600W at 120V 28,800W at 120V
12V 43,200W at 120V 57,600W at 120V
To illustrate the same point from the opposite perspective, a heating
element rated for 120 volts will draw reduced load current as indicated by
the following table. A standard 2,000 watt / 120 Vac heating element is used
as the reference.
Voltage Power Current
120V 2000 W 16.7 A
60V (48V nominal) 500 W 8.3 A
30V (24V nominal) 125 W 4.2 A
15V (12V nominal) 31 W 2.1 A
Whether using dc rated loads (the first table) or 120V elements, the total
diversion load current must not exceed the current rating of the TriStar.
6.4.5 Minimum Diversion Load
The diversion load must be large enough to divert all the current produced by the
source (wind, hydro, etc.). This value is the maximum battery voltage times the
maximum source current.
For example, if a hydro source can generate up to 30 amps of current in a
nominal 48 volt system (60V maximum), the minimum diversion load size =
60V x 30A = 1,800 watts (for loads rated at 60 volts).
General Sizing Example
Consider a 24V system with a wind turbine that is rated to generate 35A
of current. A TriStar-45 will not provide the 150% diversion load margin, and
the TS-45 is only rated for 30A of source current. The TS-45 will not provide
enough margin for wind gusts and overloads, so a TS-60 should be used.
The diversion load should be sized for 52.5A (150% of the source current) up
to 60A (the rating of the TriStar-60). If 55A is selected for the diversion load,
the load must be capable of diverting 55A at 30V (maximum battery voltage).
If a 30V heating element is used, it would be rated for 1,650 watts (or from
1,575W to 1,800W per the load range noted above).
If a 2,000 watt / 120 volt heating element is used, 13 of these elements in parallel
will be required for the diversion load (4.2 amps per element [Table
in 6.4.4] x 13 = 54.6 amps).