General Aspects Of Emc - Danfoss VLT DriveMotor FCP 106 Design Manual

Product Overview
Up to 8 preset references can be programmed in the
frequency converter. Select the active preset reference
2 2
using digital inputs or the serial communications bus. The
reference can also be supplied externally, most commonly
from an analog input. Select this external source via the 3
reference source parameters:
•
Parameter 3-15 Reference 1 Source.
•
Parameter 3-16 Reference 2 Source.
•
Parameter 3-17 Reference 3 Source.
Sum all reference resources and the bus reference to
produce the total external reference. Select the external
reference, the preset reference, or the sum of the 2 as the
active reference. Finally, this reference can by be scaled
using parameter 3-14 Preset Relative Reference.
The scaled reference is calculated as follows:
Reference = X + X ×
Where X is the external reference, the preset reference, or
the sum of these references, and Y is parameter 3-14 Preset
Relative Reference in [%].
If Y, parameter 3-14 Preset Relative Reference, is set to 0%,
scaling does not affect the reference.
2.5.2 Feedback Handling
Feedback handling can be configured to work with
applications requiring control. Configure the feedback
source via parameter 20-00 Feedback 1 Source.
2.5.3 Feedback Conversion
In some applications, it may be useful to convert the
feedback signal. One example of this is using a pressure
signal to provide flow feedback. Since the square root of
pressure is proportional to flow, the square root of the
pressure signal yields a value proportional to the flow. See
Illustration 2.17.
Ref.
signal
Desired
ow
Illustration 2.17 Feedback Conversion
20
VLT
Y
100
Ref. +
PI
P 20-01
-
FB conversion
FB
Flow
P
FB
signal
P
Danfoss A/S © 06/2016 All rights reserved.
®
DriveMotor FCP 106/FCM 106

2.6 General Aspects of EMC

Burst transient is conducted at frequencies in the range
150 kHz to 30 MHz. The inverter, the motor cable, and the
motor generate airborne interference from the frequency
converter system in the range 30 MHz to 1 GHz.
Capacitance in the motor cable coupled with a high dU/dt
from the motor voltage generates leakage currents.
The use of a screened motor cable increases the leakage
current (see Illustration 2.18) because screened cables have
higher capacitance to ground than unscreened cables. If
the leakage current is not filtered, it causes greater
interference on the mains in the radio frequency range
below approximately 5 MHz. Since the leakage current (I
is carried back to the unit through the screen (I
only a small electromagnetic field (I
motor cable.
The screen reduces the radiated interference but increases
the low-frequency interference on the mains. Connect the
motor cable screen to the frequency converter enclosure
and to the motor enclosure. This connection is best done
by using integrated screen clamps to avoid twisted screen
ends (pigtails). Pigtails increase the screen impedance at
higher frequencies, which reduces the screen effect and
increases the leakage current (I
Mount the screen at both ends of the enclosure, if a
screened cable is used for:
•
Relay.
•
Control cable.
•
Signal interface.
•
Brake.
In some situations, however, it is necessary to break the
screen to avoid current loops.
P
Flow
)
1
), there is
3
) from the screened
4
).
4
MG03M202