Danfoss VLT AutomationDrive FC 302 Programming Manual page 62

Parameter Descriptions
2-10 Brake Function
Option:
[1] Resistor
brake
3 3
[2] AC brake Is selected to improve braking without using a
2-11 Brake Resistor (ohm)
Range:
Size [ 5.00 -
related 65535.00
*
Ohm]
2-12 Brake Power Limit (kW)
Range:
Size [ 0.001 -
related 2000.000
*
kW]
60
Function:
A brake resistor is incorporated in the system, for
dissipation of surplus brake energy as heat.
Connecting a brake resistor allows a higher DC
link voltage during braking (generating operation).
The resistor brake function is only active in
frequency converters with an integral dynamic
brake.
brake resistor. This parameter controls an
overmagnetisation of the motor when running
with a generatoric load. This function can improve
the OVC-function. Increasing the electrical losses
in the motor allows the OVC function to increase
the braking torque without exceeding the
overvoltage limit.
NOTICE
The AC brake is not as efficient as dynamic
braking with resistor.
+
AC brake is for VVC mode in both open
and closed loop.
Function:
Set the brake resistor value in Ω. This
value is used for monitoring the power
to the brake resistor in 2-13 Brake Power
Monitoring. This parameter is only active
in frequency converters with an integral
dynamic brake.
Use this parameter for values without
decimals. For a selection with 2 decimals,
use parameter 30-81 Brake Resistor (ohm).
Function:
Parameter 2-12 Brake Power Limit (kW) is
the expected average power dissipated in
the brake resistor over a period of 120 s.
It is used as the monitoring limit for
16-33 Brake Energy Average and thereby
specifies when a warning/alarm is to be
given.
To calculate parameter 2-12 Brake Power
Limit (kW), the following formula can be
used.
U br 2 V × t br s
P br,avg W =
R br Ω × T br s
P is the average power dissipated in
br,avg
the brake resistor, R is the resistance of
br
the brake resistor. t is the active
br
breaking time within the 120 s period, T
Danfoss A/S © Rev. 10/2014 All rights reserved.
®
VLT AutomationDrive FC 301/302
2-12 Brake Power Limit (kW)
Range:
2-13 Brake Power Monitoring
Option:
[0] Off
*
[1] Warning 120s
[2] Trip 120s
[3] Warning & trip
120s
[4] Warning 30s
[5] Trip 30s
[6] Warning & trip
30s
[7] Warning 60s
[8] Trip 60s
[9] Warning & trip
60s
[10] Warning 300s
[11] Trip 300s
.
br
Function:
U is the DC voltage where the brake
br
resistor is active. This depends on the unit
as follows:
T2 units: 390 V
T4 units: 778 V
T5 units: 810 V
T6 units: 943 V/1099 V for D – F frames
T7 units: 1099 V
NOTICE
If R is not known, or if T
br br
different from 120 s, the practical
approach is to run the brake
application, read out 16-33 Brake
Energy Average and then enter this
+ 20% in 2-12 Brake Power Limit
(kW).
Function:
This parameter is only active in frequency
converters with a brake.
This parameter enables monitoring of the
power to the brake resistor. The power is
calculated on the basis of the resistance
(parameter 2-11 Brake Resistor (ohm)), the
DC link voltage, and the resistor duty time.
No brake power monitoring required.
Activates a warning on the display when
the power transmitted during the duty
time exceeds 100% of the monitoring limit
(parameter 2-12 Brake Power Limit (kW).
The warning disappears when the
transmitted power falls below 80% of the
monitoring limit.
Trips frequency converter and displays an
alarm when the calculated power exceeds
100% of the monitoring limit.
Activates both of the above, including
warning, trip and alarm.
MG33MJ02
is