Danfoss VLT AutomationDrive FC 300 Programming Manual page 58

Parameter Descriptions
2-10 Brake Function
Option:
[1] Resistor
brake
3 3
[2] AC brake
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]
56
VLT
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.
Is selected to improve braking without using a
brake resistor. This parameter controls an
overmagnetization 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 over voltage limit. Please note that
AC brake is not as effective as dynamic breaking
with resistor.
AC brake is for VVC plus and flux mode in both
open and closed loop.
Function:
Set the brake resistor value in Ohms.
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 two
decimals, use 30-81 Brake Resistor
(ohm).
Function:
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 /2 min and thereby specifies when a
warning/ alarm is to be given.
To calculate 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 breaking
br
time within the 120 s period, T
U is the DC voltage where the brake
br
resistor is active. This depends on the unit
as follows:
MG33MG02 - VLT
®
AutomationDrive Programming Guide
2-12 Brake Power Limit (kW)
Range:
2-13 Brake Power Monitoring
Option:
[0] Off
[1] Warning
[2] Trip
[3] Warning
and trip
If power monitoring is set to [0] Off or [1] Warning, the
brake function remains active, even if the monitoring limit
is exceeded. This may lead to thermal overload of the
resistor. It is also possible to generate a warning via a
relay/digital outputs. The measuring accuracy of the power
monitoring depends on the accuracy of the resistance of
the resistor (better than ±20%).
2-15 Brake Check
Option: Function:
Select type of test and monitoring function to check the
connection to the brake resistor, or whether a brake
resistor is present, and then display a warning or an
.
br
alarm in the event of a fault.
®
is a registered Danfoss trademark
Function:
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
NOTE
If R is not known or if T
br
from 120 s, the practical approach is
to run the brake application, readout
16-33 Brake Energy /2 min and then
enter this + 20% in 2-12 Brake Power
Limit (kW).
Function:
This parameter is only active in frequency
converters with an integral dynamic brake.
This parameter enables monitoring of the power
to the brake resistor. The power is calculated on
the basis of the resistance (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 over 120 s exceeds 100% of
the monitoring limit (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.
is different
br