bonitron M3534-I3, Руководство для пользователей

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M3534
46
The process described below is a good way to estimate the capacitor bank required.
Since the discharge characteristic of a capacitor bank with a constant power load is a
nonlinear differential equation, optimizing the capacitor bank selection is an iterative
process. A general estimate of needs must be used to build a capacitor bank and then
the actual values must be cross checked to make sure they are suitable.
There are several steps in the process. The capacitor bank will be comprised of
capacitors connected in series for voltage support, with one or more strings in parallel
to support the energy requirements. Since the extraction losses due to the
electrostatic resistance (
𝐸𝑠𝑟
) of the capacitor can be significant, they must be taken
into account. If the
𝐸𝑠𝑟
losses get too high, parallel capacitor strings can be used to
reduce the current in each series string.
The steps to specify the string will include:
1.
Determine the energy required for the outage.
2.
Determine the minimum voltage acceptable for full power backup.
3.
Determine the maximum current required to support the load at minimum
voltage.
4.
Specify the capacitor to be evaluated.
5.
Estimate the losses for each capacitor.
6.
Determine the minimum number of capacitors per series string required for the
minimum voltage.
7.
Add capacitors in series for outage energy.
8.
Determine if parallel strings are required to provide outage energy.
These are the definitions of the variables we will use in the following equations:
𝐶
- Capacitance at end of life
𝐶
- Total capacitance of the entire cap bank
𝐸𝑠𝑟
- Total equivalent ESR for the entire cap bank
𝐸𝑠𝑟
- Internal resistance at end of life
𝐼
- Peak current into the M3534 during the discharge cycle
𝐽
- Total energy in charged capacitor bank prior to discharge
𝐽
- Total losses during discharge
𝐽
- Energy required to hold up the system during the outage
𝑛
- Number of capacitors in each series string
𝑃
- System power in kilowatts
𝑇
- Time outage in seconds
𝑉
- Charge voltage at beginning of discharge
𝑉
- The capacitor string voltage at the end of the discharge
𝑉
- Maximum charge voltage for the capacitor
𝑉
- Lowest voltage the capacitor bank can reach
𝑉
- Terminal voltage of an individual capacitor during discharge