Step 5. Set up the desired limits for speed and ramp
time.
•
Parameter 4-11 Motor Speed Low Limit [RPM] or
parameter 4-12 Motor Speed Low Limit [Hz]
•
Parameter 4-13 Motor Speed High Limit [RPM] or
parameter 4-14 Motor Speed High Limit [Hz]
•
Parameter 3-41 Ramp 1 Ramp-up Time
•
Parameter 3-42 Ramp 1 Ramp-down Time
4.4 Additional Connections
4.4.1 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, for example due to the load
being too heavy.
•
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 is engaged 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], 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.
4.4.2
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
M,N
for
the adjustable frequency drive.
NOTICE!
Installations with cables connected in a common joint as
in Figure 4.32 are only recommended for short cable
lengths.
NOTICE!
When motors are connected in parallel,
parameter 1-29 Automatic Motor Adaptation (AMA) cannot
be used.
NOTICE!
The electronic thermal relay (ETR) of the adjustable
frequency drive cannot be used as motor overload
protection for the individual motor in systems with
parallel-connected motors. Provide further motor
overload protection, for example thermistors in each
motor or individual thermal relays (circuit breakers are
not suitable as protection).
Figure 4.32 Parallel Motor Connection
Problems may arise at start-up and at low RPM values if
motor sizes are widely dierent because small motors'
relatively high ohmic resistance in the stator calls for a
higher voltage at start-up and at low RPM values.
Electrical Installation
VLT
®
HVAC Drive FC 102
64 Danfoss A/S © 08/2014 All rights reserved. MG11F522
44
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