2-11 Brake Resistor (ohm)
Range:
Function:
Size
related
*
[5.00 -
65535.00
Ohm]
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
2-12 Brake Power Limit (kW)
Range:
Function:
Size
related
*
[0.001 -
2000.000
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
,
the following formula can be used.
Pbr,avg W =
Ubr2 V × tbr s
Rbr Ω × Tbr s
P
br,avg
is the average power dissipated in
the brake resistor, R
br
is the resistance of
the brake resistor. t
br
is the active breaking
time within the 120 s period, T
br
.
U
br
is the DC voltage where the brake
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
NOTE
If R
br
is not known or if T
br
is 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)
.
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
2-13 Brake Power Monitoring
Option:
Function:
), 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 (
).
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
and trip
Activates both of the above, including
warning, 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:
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.
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.
If the DC link ripple amplitude while braking
is lower than the DC link ripple amplitude
before b 1%:
Brake check has failed by
returning a warning or alarm.
4.
If the DC link ripple amplitude while braking
is higher than the DC link ripple amplitude
before b 1%:
Brake check is OK.
[0]
*
Off Monitors brake resistor and brake IGBT for a short-
circuit during operation. If a short-circuit occurs,
warning 25 appears.
Parameter Descriptions
VLT
®
AutomationDrive Programmming Guide
52
MG33ME02 - VLT
®
is a registered Danfoss trademark
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