28
(a)
Auto acting – breaker
This external interrupt method will allow the manual resetting of the external breaker if an overload condition exists. A single breaker
is used for each Evolion or on pair of parallel connected Evolions. The breaker acts with specific time/current characteristics. Consult
with your local Saft representative for more details on the breaker type.
(b)
Contactor – RS485, dry contactor
This external interrupt method will allow the automatic opening and closing of an external contactor piloted by the RS485/Modbus.
The dry contact communication with the parallel connected Evolions will also work by using a low %SOC or 42 V LVD signal. Options to
use several distributed contactors or one main contactor is conceivable. If several distributed contactors are used, then the contactors
must act “simultaneously” when the opening signal is commanded.
13.2 Thermal characteristics in cycling
Heat is generated during charge and discharge. The amount of heat generated is directly proportional to the level of current and the
internal resistance of the Evolion. The Evolion may accumulate heat in frequent cycling applications.
For frequent cycling application limiting the current on charge and discharge will also limit the maximum steady state temperature of
the Evolion in cycling. A good rule of thumb is to not exceed 25 Amps of re-charge current per Evolion in applications where more than
2 cycles per day and less than 5 cycles per day are needed.
Examples of frequent cycling applications include poor AC grid cycling and hybrid power cycling. In both cases the Evolion charges and
discharges continuously from one cycle to the next where there is no/or little floating or resting between cycles.
In order to estimate the maximum temperature difference (dTmax) a correlation can be used to calculate it. The Evolion typically
reaches a peak temperature in frequent cycling at the end of the re-charge part of the cycle. After about 3 days of continuous cycling,
this peak temperature or dTmax will stabilize. To estimate this dTmax, the following equations can be used. First calculate
I
rms
using
Equation 1 and the values of charge and discharge current planned for continuous cycling use (per each Evolion). After, plug the result
of Equation 1 into Equation 2 to estimate the
dTmax.
Equation 1
I
rms
weighted average current for one cycle (result used to input to dTmax equation below)
I
Ch
Charge current for one module (each cycle), from sizing output
I
Dch
Discharge current for one module (each cycle), from sizing output
t
Ch
Time on charge for 1 cycle, from sizing output
t
Dch
Time on discharge for 1 cycle, from sizing output
t
cycle
Total time for one cycle (tCh + tDch)
Equation 2
dTmax Maximum expected stabilized temperature difference from the ambient environment
I
rms
weighted average current for one cycle
A correlation of dTmax to I
rms
is shown if Figure 19. The results of actual test data are indicated and compared to Equation 2.
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