Xylem Aquavar, Instruction Manual

Page: 59 / 172

without connection to line power. Please note that a warning of low voltage will be given
when 24 V DC has been connected; however, there will be no tripping.
Electrical Hazard:
Use 24 V DC supply of type PELV to ensure correct galvanic isolation (type PELV) on the
control terminals of the adjustable frequency drive.
5.15.2 Access to control terminals
All terminals to the control cables are located beneath the LCP. They are accessed by
opening the door of the IP21/54 version or removing the covers of the IP00 version.
5.15.3 Control cable and connection
• Isolate control wiring from high power components in the adjustable frequency drive
• If the adjustable frequency drive is connected to a thermistor, for PELV isolation,
optional thermistor control wiring must be reinforced/double insulated. A 24 V DC
supply voltage is recommended.
Using shielded control cables
Xylem recommends braided shielded/armored cables to optimize EMC immunity of the
control cables and the EMC emission from the motor cables.
The ability of a cable to reduce the incoming and outgoing radiation of electric noise
depends on the transfer impedance (Z
T
). The shield of a cable is normally designed to
reduce the transfer of electric noise; however, a shield with a lower transfer impedance
(Z
T
) value is more effective than a shield with a higher transfer impedance (Z
T
).
Transfer impedance (Z
T
) is rarely stated by cable manufacturers, but it is often possible to
estimate transfer impedance (Z
T
) by assessing the physical design of the cable.
Transfer impedance (Z
T
) can be assessed on the basis of the following factors:
• The conductibility of the shield material
• The contact resistance between the individual shield conductors
• The shield coverage, i.e., the physical area of the cable covered by the shield - often
stated as a percentage value
• Shield type, i.e., braided or twisted pattern
a Aluminum-clad with copper wire
b Twisted copper wire or armored steel wire cable
c Single-layer braided copper wire with varying
percentage shield coverage.
d This is the typical reference cable.
e Double-layer braided copper wire
f Twin layer of braided copper wire with a magnetic,
shielded/armored intermediate layer Cable that runs in
copper tube or steel tube
g Lead cable with 0.043 in [1.1 mm] wall thickness
5 Electrical Installation
Aquavar ® Intelligent Pump Controller - 150 HP to 600 HP INSTRUCTION MANUAL 57