Additional Connections; Serial Communication; Mechanical Brake Control; Parallel Connection Of Motors - Danfoss VLT AutomationDrive FC 302 Installation Manual

Electrical Installation

4.9 Additional Connections

4.9.1 Serial Communication

RS-485 is a 2-wire bus interface compatible with multi-drop
network topology, i.e., nodes can be connected as a bus,
or via drop cables from a common trunk line. A total of 32
nodes can be connected to one network segment.
Repeaters divide network
NOTICE!
Each repeater functions as a node within the segment in
which it is installed. Each node connected within a given
network must have a unique node address across all
segments.
Terminate each segment at both ends using either the
termination switch (S801) of the adjustable frequency
drives or a biased termination resistor network. Always use
shielded twisted pair (STP) cable for bus cabling, and
always follow good common installation practice.
Low-impedance ground connection of the shield at every
node is important, including at high frequencies. Thus,
connect a large surface of the shield to ground, for
example, with a cable clamp or a conductive cable
connector. It may be necessary to apply potential-
equalizing cables to maintain the same ground potential
throughout the network - particularly in installations with
long cables.
To prevent impedance mismatch, always use the same
type of cable throughout the entire network. When
connecting a motor to the adjustable frequency drives,
always use shielded motor cable.
Cable Shielded twisted pair (STP)
120 Ω
Impedance
Max. 4000 ft [1200 m] (including drop lines)
Cable length
Max. 1,650 ft [500 m] station-to-station
Table 4.10 Cable Recommendations

4.9.2 Mechanical Brake Control

In hoisting/lowering applications, it is necessary to be
able to control an electro-mechanical brake:
•
Control the brake using any relay output or
digital output (terminal 27 or 29).
•
Keep the output closed (voltage-free) as long as
the adjustable frequency drive is unable to
'support' the motor, e.g., due to the load being
too heavy.
MG37A322
Installation Manual
•
•
•
If the adjustable frequency drive is in alarm mode or in an
overvoltage situation, the mechanical brake immediately
cuts in.

4.9.3 Parallel Connection of Motors

The adjustable frequency drive can control several motors
connected in parallel. The total current consumption of the
motors must not exceed the rated output current I
the adjustable frequency drive.
Danfoss A/S © Rev. 04/2015 All rights reserved.
Select [32] Mechanical brake control in parameter
group 5-4* Relays for applications with an electro-
mechanical brake.
The brake is released when the motor current
exceeds the preset value in
parameter 2-20 Release Brake Current.
The brake engages when the output frequency is
less than the frequency set in
parameter 2-21 Activate Brake Speed [RPM] or
parameter 2-22 Activate Brake Speed [Hz], only if
the adjustable frequency drive completes a stop
command.
4 4
for
M,N
47