Additional Connections; Mechanical Brake Control; Motor Thermal Protection - Danfoss VLT AutomationDrive FC 300 Operating Instructions Manual

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VLT AutomationDrive FC 300 Operating
Instructions

3.7 Additional Connections

3.7.1 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 frequency converter is unable to 'support' the motor, for example due to the load being
too heavy.
Mechanical brake control
• Select
• The brake is released when the motor current exceeds the preset value in par. 2-20
• The brake is engaged when the output frequency is less than the frequency set in par. 2-21
Brake Speed [Hz]
, and only if the frequency converter carries out a stop command.
If the frequency converter is in alarm mode or in an over-voltage situation, the mechanical brake immediately cuts in.
3.7.2 Parallel Connection of Motors
The frequency converter can control several parallel-connected motors.
The total current consumption of the motors must not exceed the rated
output current I for the frequency converter.
M,N
NB!
Installations with cables connected in a common joint
as in the illustration below, is only recommended for
short cable lengths.
NB!
When motors are connected in parallel, par. 1-29
tomatic Motor Adaptation (AMA)
NB!
The electronic thermal relay (ETR) of the frequency
converter cannot be used as motor protection for the
individual motor in systems with parallel-connected
motors. Provide further motor protection by e.g. ther-
mistors in each motor or individual thermal relays (cir-
cuit breakers are not suitable as protection).
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.

3.7.3 Motor Thermal Protection

The electronic thermal relay in the frequency converter has received UL-approval for single motor protection, when par. 1-90
tion ETR Trip
is set for and par. 1-24
For thermal motor protection it is also possible to use the MCB 112 PTC Thermistor Card option. This card provides ATEX certificate to protect motors in
explosion hazardous areas, Zone 1/21 and Zone 2/22. Please refer to the
[32] in par. 5-4* for applications with an electro-mechanical brake.
Au-
cannot be used.
Motor Current
is set to the rated motor current (see motor name plate).
MG.33.AC.02 - VLT is a registered Danfoss trademark
Release Brake Current
Activate Brake Speed [RPM]
Design Guide for further information.
3 How to Install
.
or par. 2-22 Activate
Motor Thermal Protec-
3
35