Eurotherm 584SV Series, Product Manual

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If connecting multiple motors to a single VSD, use a star junction point for motor cable
connections. Use a metal box with entry and exit cable glands to maintain shield integrity.
Refer to Chapter 13: “Using Multiple Motors on a Single Inverter”.
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A star-point earthing policy separates `noisy’ and `clean’ earths. Four separate earth busbars
(three are insulated from the mounting panel) connect to a single earth point (star point) near the
incoming safety earth from the main supply. Flexible, large cross-section cable is used to ensure
a low HF impedance. Busbars are arranged so that connection to the single earth point is as short
as possible.
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Used as a reference point for all signal and control cabling. This may be further subdivided into
an analogue and a digital reference busbar, each separately connected to the star earthing point.
The digital reference is also used for any 24V control.
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Used for all power earths, i.e. protective earth connection. It is also used as a reference for any
110 or 220V control used, and for the control transformer screen.
Doors
Metal
Work
110V
Control
24V Control
unscreened signals
STAR POINT
Incoming Safety Earth (PE)
Analogue Clean Earth
Dirty Earth
Digital Clean Earth
Signal/Control Screen
all screened signals not
Back Panel
U-clip used to terminate screen
connection to the back panel
PE = Protective Earth
0A = 0 Volts Analogue
0D = 0 Volts Digital
f = External Filter
VSD = Variable Speed Drive
PLC = Programmable Logic Controller going directly to a VSD
Metal Work Earth
Back
Panel
PLC
PE
PE
PE 0D 0D 0D 0D 0A 0A 0A
to motor to motor to motor
screened screened
PE
VSD VSD VSD
f
f f
f
PE PE PE
Figure 12-2 Star Point Earthing