Webasto 900EX, Installation, Operation And Maintenance Manual

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4.4 CHOOSING OPERATING LIMITS
The 900 EX allows the set up of temporary upper and lower Operating Limits for
voltage, current, and power that are more restrictive than the absolute system
limits defined in the Operating Range table. In many cases, these more restrictive
limits may be useful in order to protect the load or avoid unsafe conditions.
For example, in order to protect a battery from overcharging, set an upper
voltage limit of 280 Volts, which is substantially below the absolute 900 Volt
limit allowed. Similarly, a lower voltage limit could be used to protect against
over-discharging.
4.4.1 GENERAL LIMIT CONSIDERATIONS
• Set the upper/lower limits higher/lower than the maximum/minimum commanded
values.
• Avoid over/under limit shutdown (caused by commanding modes higher/lower
than the set limits).
4.4.2 OPERATING SPACE
The Operating Limits define the Operating Space of the DC Converter. The
maximum Operating Space was depicted in the previous section. By setting more
restrictive Operating Limits, the Operating Space is reduced.
When operating inside the limits of the Operating Space, the DC Converter will
control the output based on the selected Control Mode and value. However, if
one of the boundaries of the Operating Space is reached, the DC Converter will
override the selected Control Mode and use the boundary condition as its internal
Control Mode, if necessary, to stay within the Operating Space.
4.4.3 SECOND BOUNDARY
If a second boundary is encountered, the DC Converter will again override the
Control Mode and use the second boundary as the internal Control Mode, if
necessary, to stay within the Operating Space. If the DC Converter is unable to
maintain the limits set, it will automatically disconnect the output terminals to
protect the system and/or the load from a damaging failure. In summary, the DC
Converter will follow the limits originally set in all cases.
4.4.4 LOAD
The load must exist in the Operating Space defined by the limits. A simple
sketch to determine the desired Operating Space will be useful and may avoid
frustration. There are a few basic rules that must be followed in setting the