Danfoss VLT AutomationDrive FC 300 Programming Manual page 51

Parameter Descriptions
2-11 Brake Resistor (ohm)
Range:
Size [5.00 -
related 65535.00
*
Ohm]
3 3
2-12 Brake Power Limit (kW)
Range:
Size [0.001 -
related 2000.000
*
kW]
2-13 Brake Power Monitoring
Option:
[0] Off
*
50
FC 300 Programming Guide
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 120s. 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 the
br,avg
brake resistor, R is the resistance of the
br
brake resistor. t is the active breaking time
br
within the 120 s period, T .
br
U is the DC voltage where the brake
br
resistor is active. This depends on the unit as
follows:
T2 units: 390V
T4 units: 778V
T5 units: 810V
T6 units: 943V / 1099V for D – F frames
T7 units: 1099V
If R is not known or if T is different from
br br
120s, 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.
MG.33.MB.02 - VLT
2-13 Brake Power Monitoring
Option: Function:
[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 Off [0] or Warning [1], 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 alarm in the event of a
fault.
NOTE
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.
2.
3.
4.
[0] Off Monitors brake resistor and brake IGBT for a short-
circuit during operation. If a short-circuit occurs,
*
warning 25 appears.
®
is a registered Danfoss trademark
The DC link ripple amplitude is measured
for 300 ms without braking.
The DC link ripple amplitude is measured
for 300 ms with the brake turned on.
If the DC link ripple amplitude while
braking is lower than the DC link ripple
amplitude before braking + 1 %: Brake
check has failed by returning a warning or
alarm.
If the DC link ripple amplitude while
braking is higher than the DC link ripple
amplitude before braking + 1 %: Brake
check is OK.