- page 20 -
CASE STUDY 11
Voltage Dip in a Factory
Environment:
Analysis:
Target: A factory in Southeast Asia, 1-phase 2-wire, 100V circuit
Problem:
Power supply is damaged.
Voltage fluctuation1.
The following power characteristics were concluded from this 2 week voltage fluctuation graph.
Voltage Fluctuation
No.1
No.2
No.3
Unfortunately, sufficient event data was not recorded in No.1 and No.2. , so that detailed
analysis was not possible. The important point to note is that a large voltage fluctuation
occurred between 9 p.m. and 9 a.m. everyday (No.3), and the fluctuation was about 50V
(between 75Vrms and 125Vrms).
Event data2.
The voltage dip (instantaneous voltage drop) occurred frequently at night. Only 5 voltage
dips were detectable in a 1s period. The situation of voltage dip occurrence demonstrates
the same tendency.
This is the analysis of one voltage dip event.
When the depth of the voltage dip reaches 90Vrms, the power supply is switched
from the commercial supply to the UPS.
(1)
When the power supply is switched to the UPS, the voltage RMS value increases to
116Vrms (125Vrms maximum).
(2)
The voltage waveform changes from the sine wave to the square wave in the UPS
supply.
(3)
The square wave continues for about 1.25s(4)
(5)
The power supply is changed from the UPS to the commercial supply later. Upon
this switching, the voltage drops to 78Vrms (75Vrms minimum) for a short period.
1
2
3
Supply voltage
Maximum
Minimum
Average
Voltage fluctuation graph
No.1 (blue)
No.2 (green)
Voltage value
131.67Vrms
0.15Vrms
98Vrms
To Next Page
Loading...
