Power and Voltage Quality Trainer
AD 2
– MI 3399
133
electronic drives and switchers failure rate increases if THDU rises above 8%
2.8.1 Interharmonics
Interharmonics are harmonics that are not an integer multiplication of the fundamental
frequency. The main sources of interharmonic waveform distortion are static frequency
converters, induction motors and arcing devices.
2.8.2 Total Harmonic Distortion (THD)
THD is the ratio of a wave’s harmonic content (for voltage or current) to its fundamental
component.
2.9 Supply voltage unbalance
Supply voltage unbalance
arises when rms values or phase angles between
consecutive phases are not equal. Term
imbalance
is also used as an alternative.
Supply voltage unbalance is defined as the ratio of the negative sequence component
to the positive sequence.
%
100
%
100
sequence
postive
sequence
negative
V
V
u
d
i
u
Origin
Unbalance happens when current consumption is not balanced or during a faulty
condition before tripping.
Impact on customers’ equipment
Voltage unbalance affects three phase asynchronous motors causing overheating and
a tripping of protective devices.
2.10 Flicker
Flicker is a visual sensation caused by unsteadiness of a light. The level of the
sensation depends on the frequency and magnitude of a light change and on the
observer.
Changing of a lighting flux can be correlated to a voltage envelope in the following
figure.
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...
Page 74: ...Electrical Installation Safety Trainer AD 1 MI 3399 74...
Page 197: ...Power and Voltage Quality Trainer AD 2 MI 3399 197 Figure 4 89 Transient Chart view...
Page 204: ...PAT Appliances Machines Safety Trainer AD 3 MI 3399 204...
Page 249: ...PV Photovoltaic Systems Trainer AD 4 MI 3399 249...
Page 250: ...PV Photovoltaic Systems Trainer AD 4 MI 3399 250 AD 4 MI 3399 PV Photovoltaic Systems Trainer...