Power and Voltage Quality Trainer
AD 2
– MI 3399
134
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-400
-300
-200
-100
0
100
200
300
400
time (s)
voltage(V)
Figure 2-4: voltage fluctuation
Origin
Origins of voltage fluctuation are arc furnaces, welding machines and similar heavy
loads that consume greatly varying currents. Flicker can arise in the presence of
interharmonics with a frequency close to the base frequency or harmonic.
Impact to customers’ equipment
Magnitude of voltage fluctuation is usually below 3% of supply voltage and does not
have any noticeable influence to equipment. Flickering caused by voltage fluctuation
of just 0.2% with frequency of 9 Hz is considered as annoying.
2.11 Inrush
Current needed to start a motor can be 10 to 15 times the normal operating current.
This initial surge of current can cause dips in voltage and can be hard to analyse with
normal test instruments, for this reason an analyser with a fast logging function is
required.
2.12 Transient overvoltages
Transient is a term for
short, highly damped
momentary voltage or current
disturbance.
There are two types of transient overvoltages:
impulsive overvoltage
oscillatory overvoltage
Origin
Impulsive transient overvoltages
are
unidirectional
disturbances caused by lighting
and have a high magnitude but low energy. Frequency range is above 5kHz with
duration 30-200 microseconds.
Oscillatory transient overvoltages
are caused by switching, Ferro resonance or can
arise as a system response to an impulsive overvoltage. Switching overvoltages have
Summary of Contents for MI 3399
Page 27: ...Electrical Installation Safety Trainer AD 1 MI 3399 27...
Page 46: ...Electrical Installation Safety Trainer AD 1 MI 3399 46 3 Exit settings...
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Page 197: ...Power and Voltage Quality Trainer AD 2 MI 3399 197 Figure 4 89 Transient Chart view...
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