Danfoss VLT AutomationDrive FC 301 Programming Manual page 57

Parameter Descriptions
2-10 Brake Function
Option: Function:
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. Note that AC brake is not as effective as
dynamic breaking with resistor.
AC brake is for VVC
open and closed loop.
2-11 Brake Resistor (ohm)
Range: Function:
Set the brake resistor value in Ω. This
Size [ 5.00 -
related 65535.00 value is used for monitoring the power
*
Ohm]
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 30-81 Brake Resistor (ohm).
2-12 Brake Power Limit (kW)
Range: Function:
Size [ 0.001 - 2-12 Brake Power Limit (kW) is the expected
related 2000.000 average power dissipated in the brake
*
kW] 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.
P br,avg W =
P is the average power dissipated in
br,avg
the brake resistor, R
the brake resistor. t
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:
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
different 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).
®
VLT AutomationDrive FC 301/302 Programming Guide
plus
and flux mode in both
U br 2 V × t br s
R br Ω × T br s
is the resistance of
br
is the active breaking
br
.
br
is
br
MG33MH02 - Rev. 2013-09-30
2-13 Brake Power Monitoring
Option: 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.
[0] Off No brake power monitoring required.
*
[1] Warning 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.
[2] Trip Trips frequency converter and displays an alarm
when the calculated power exceeds 100% of
the monitoring limit.
[3] Warning Activates both of the above, including warning,
and trip trip and alarm.
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:
2-15 Brake Check is only active in frequency converters
with an integral dynamic brake.
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 alarm in the event of a fault.
NOTICE
The brake resistor disconnection function is
tested during power-up. However the brake
IGBT test is performed when there is no
braking. A warning or trip disconnects the
brake function.
The testing sequence is as follows:
1. The DC-link ripple amplitude is measured for
300 ms without braking.
2. The DC-link ripple amplitude is measured for
300 ms with the brake turned on.
3 3
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