# Siemens Micromaster 420 Operating Instruction Page 77

5. SYSTEM PARAMETERS
Parameter
Number
Note:
The inverter starts at f
If this is being used to hold the motor at a certain frequency against a mechanical brake (i.e.
you are using a relay to control a mechanical brake), it is important that f
otherwise, the current drawn may be too high and the relay may not open as inverter is in
current limit.
A typical value of f
You can calculate the rated slip frequency by using the following formula:
n
– n
syn
rated
__________________
n
syn
P1217
Holding time after ramp down
Defines the time at which the inverter runs at f
P1215 diagram).
P1232
DC braking current
Defines level of DC current as a percentage of nominal motor current (P0305).
P1233
Duration of DC braking
Defines duration for which DC injection braking is to be active following an OFF1 command.
Possible settings:
0
=
1 – 250 =
Note
The DC braking function causes the motor to stop rapidly by applying a DC braking current
(the current applied also holds the shaft stationary). When the DC braking signal is applied,
the inverter output pulses are blocked and the DC current is only applied once the motor
has been sufficiently demagnetized. (Demagnetization time is automatically calculated from
Motor data).
Warning
Frequent use of long periods of DC braking can cause the motor to overheat.
P1236
Compound braking current
Defines DC level superimposed on AC waveform. This form of braking becomes active
following an OFF1 / OFF3 command.
Increasing the value will generally improve braking performance; however, if you set the
value too high, an overvoltage trip may result.
Possible settings:
0
=
1 – 250
=
MICROMASTER 420 Operating Instructions
6SE6400-5AA00-0BP0
Parameter Name
on this profile, i.e. it does not use a ramp.
min
for this type of application is the slip frequency of the motor.
min
x f
rated
not active following OFF1
active for the specified duration
Compound braking disabled
Level of DC braking current defined as a % of motor rated current
(P0305)
< 5 Hz;
min
after ramping down at point 2 (as shown in
min
International English
♦ ♦ ♦ ♦ P0003 User
Min
Access Level
Max
♦ ♦ ♦ ♦ P0004 Setting
[Default]
♦ ♦ ♦ ♦ Changeable
Units
♦ ♦ ♦ ♦ Status
0
2
20
12
[1]
s
0
2
250
12
[100]
'•'
%
0
2
250
12
[0]
'•'
s
0
2
250
12
[0]
'•'
%
77

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