Trane TR170 - Effects of EMI; Sources of EMI

5.2.4 Eects of EMI
While electromagnetic interference-related (EMI) distur-
bances to the operation of the frequency converter are
uncommon, the following detrimental EMI eects
sometimes occur:
•
Motor speed
uctuations.
•
Serial communication transmission errors.
•
Frequency converter CPU exception faults.
•
Unexplained frequency converter trips.
A disturbance resulting from other nearby equipment is
more common. Generally, other industrial control
equipment has a high level of EMI immunity. However,
non-industrial, commercial, and consumer equipment is
often susceptible to lower levels of EMI.
Detrimental eects to these systems include the following:
•
Pressure/ow/temperature signal transmitter
signal distortion or aberrant behavior.
•
Radio and TV interference.
•
Telephone interference.
•
Computer network data loss.
•
Digital control system faults.
5.2.5 Sources of EMI
Modern frequency converters (see Illustration 5.1) utilize fast-switching electronic devices to generate the modulated output
voltage waveform necessary for accurate motor control. These devices rapidly switch the xed DC-link voltage creating a
variable frequency, and variable voltage PWM waveform. This high rate of voltage change [dU/dt] is the primary source of
the frequency converter generated EMI.
The high rate of voltage change caused by the IGBT switching creates high frequency EMI.
1RFI lter 6 PWM waveform
2Rectier 7 IGBT
3DC link 8 Filter reactor
4Inverter 9 Sine-wave
5Motor 10 AC line
Illustration 5.1 Frequency Converter Principle Diagram
Frequency Converter and Mot...
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