Operating instructions

5. SYSTEM PARAMETERS International English
MICROMASTER 420 Operating Instructions 77
6SE6400-5AA00-0BP0
Parameter
Number
Parameter Name
Min
Max
[Default]
Units
♦
♦♦
♦P0003 User
Access Level
♦
♦♦
♦P0004 Setting
♦
♦♦
♦Changeable
♦
♦♦
♦Status
Note:
The inverter starts at f
min
on this profile, i.e. it does not use a ramp.
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
min
< 5 Hz;
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
min
for this type of application is the slip frequency of the motor.
You can calculate the rated slip frequency by using the following formula:
n
syn
– n
rated
__________________
x f
rated
n
syn
Holding time after ramp downP1217
Defines the time at which the inverter runs at f
min
after ramping down at point 2 (as shown in
P1215 diagram).
0
20
[1]
s
2
12
DC braking currentP1232
Defines level of DC current as a percentage of nominal motor current (P0305).
0
250
[100]
%
2
12
‘•’
Duration of DC braking after OFF1P1233
Defines duration for which DC injection braking is to be active following an OFF1 command.
Possible settings:
0 = not active following OFF1
1 – 250 = active for the specified duration
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.
0
250
[0]
s
2
12
‘•’
Compound braking currentP1236
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 = Compound braking disabled
1 – 250 = Level of DC braking current defined as a % of motor rated current
(P0305)
0
250
[0]
%
2
12
‘•’