- page 16 -
CASE STUDY 8
Periodical Instantaneous Voltage Drop
Environment:
Analysis:
Target: Retail store, 1-phase 2-wire, 100V outlet
When analyzing the voltage RMS value fluctuation, the following two phenomena were observed.
(The graph shows measurement during 12 hours in the night for a period of 2 weeks.)
Problem:
No apparent trouble is detected, but the voltage fluctuation is big.
Maximum value: 106.70Vrms, Average value: 102.53Vrms, Minimum value: 93.25Vrms1)
Instantaneous voltage drop occurred every 13 minutes.2)
Voltage Fluctuation
The cause of the instantaneous voltage drop every 13 minutes is assumed to originate from an
electronic device connected to the line as this outlet is turned on or works periodically via a timer.
The device may have a high inrush current - common in equipment such as laser printers, copy
machines, electric heaters, etc. A laser printer consumes current periodically, and causes a
voltage drop as a result of its start-up current consumption. An electric heater also causes a
voltage drop from the periodic inrush current ON/OFF of the thermostat,
There are many instantaneous voltage drops, but the minimum voltage is 93.25Vrms which is
about 7% lower than the nominal voltage. Most equipment works normally at this voltage level.
To Next Page
Loading...
