i4MC&V/EN M/C User Manual
iSTAT i4MC&V
Page 21
TABLE 4-3: i4MV
Voltage U
1
Frequency f
THD of voltage U
1
Internal Temperature
The equations defining the calculated values are detailed in Appendix B
4.3.1 Voltage
The i4MV measures the RMS value of the voltage (U) connected to the meter.
4.3.2 Current
The i4MC measures the true RMS value of the phase current (
I) connected to the unit.
4.3.3 Frequency
The system frequency is calculated from the time period of the measured voltage (i4MV) or
current (i4MC).
4.3.4 Harmonics(THD)
The percentage total harmonic distortion (%THD) value is the ratio of the sum of the powers
of the harmonic frequencies above the fundamental frequency to the power of the
fundamental frequency. This sum of the powers is a geometric total, formed by taking the
square root of the sum of the squares of the amplitude of each of the harmonics.
The i4MC provides %THD values for the phase current, and the i4MV %THD value for the
voltage.
4.3.5 Maximum demands (MDs)
The i4MC stores the maximum demand value since last reset of the current, and also
provides the current or 'dynamic' maximum demand.
4.3.6 Average demands
4.3.6.1
Thermal Demand
The thermal demand option will provide an exponential thermal characteristic, based on the
bimetal element principal. Maximum demand since last reset and the dynamic Maximum
Demand are stored in the i4MC.
A time constant (t. c.) can be set from 1 to 255 minutes and is 6−time thermal time constant
(t..c. = 6 * thermal time constant).
Example:
Mode: Thermal function
Time constant: 8 min.
Current MD and maximal MD: Reset at 0 min.
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