4.10 Additional Connections
4.10.1 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, such as when the load is too
heavy, for example.
•
Select
Mechanical brake control
[32] in par. 5-4* for applications with an electro-mechanical brake.
•
The brake is released when the motor current exceeds the preset value in par. B-20
Release Brake Current
.
•
The brake is engaged when the output frequency is less than the frequency set in par. B-21
Activate Brake Speed [RPM]
or par. B-22
Activate
Brake Speed [Hz]
, and only if the adjustable frequency drive carries out a stop command.
If the adjustable frequency drive is in alarm mode or in an overvoltage situation, the mechanical brake immediately cuts in.
4.10.2 Parallel Connection of Motors
The adjustable frequency drive can control several parallel-connected
motors. The total current consumption of the motors must not exceed
the rated output current I
M,N
for the adjustable frequency drive.
NOTE!
Installation with cables connected in a common joint,
as in the figure below, is only recommended for short
cable lengths.
NOTE!
When motors are connected in parallel, par. 1-29
Au-
tomatic Motor Adaptation (AMA)
cannot be used.
NOTE!
The electronic thermal relay (ETR) of the adjustable
frequency drive cannot be used as motor protection for
the individual motor in systems with parallel-connec-
ted motors. Provide further motor protection with, for
example, thermistors in each motor or individual ther-
mal relays (circuit breakers are not suitable for pro-
tection).
Problems may arise at start and at low RPM values if motor sizes are widely different because small motors' relatively high ohmic resistance in the stator
calls for a higher voltage at start and at low RPM values.
VLT AQUA Low Harmonic Drive Instruction
Manual
4 How to Install
MG.20.T1.22 - VLT
®
is a registered Danfoss trademark
4-63
4
