Siemens MICROMASTER 440 Operating Instructions Manual page 141

Issue 10/03
~
Fig. 3-55
The braking energy in the DC link is converted into heat when dynamic braking is
activated (enabled using P1237). The energy is converted into heat using the
voltage-controlled chopper resistor (ballast resistor). Chopper resistors are used if
regenerative energy is dissipated in the DC link for a short time, e.g. when a drive
brakes and the drive should be prevented from being shutdown (tripped) with fault
message F0002 ("DC link overvoltage"). In this case, when the DC link threshold
V
DC chopper
switch (semiconductor switch).
Switch-in threshold of the chopper resistor:
If P1254 = 0 :
Otherwise :
The chopper switch-in threshold V
P1254 (Auto detect V
voltage P0210 or indirectly using the DC link voltage and r1242.
V
DC, act
V
DC, Chopper
∆
V
Fig. 3-56
The regenerative (braking) energy is converted into thermal energy using the
chopper resistor. A braking module (chopper control) is integrated in the DC link for
this purpose. The chopper of the braking module switches the resistor with a mark-
space ratio corresponding to the regenerative power to be dissipated. The braking
module is only active if, as a result of the regenerative operation, the DC link
MICROMASTER 440 Operating Instructions
6SE6400-5AW00-0BP0
MM4
=
~
Connecting the chopper (braking) resistor
is exceeded, then the chopper resistor is switched-in using an electronic
V =
DC , Chopper
=
V
DC , Chopper
switch-on levels), either directly using the line supply
DC
100 %
∆V
–
V
1
0
P1237
Duty cycle
monitoring
Mains
200 - 240 V 380 - 480 V
9.8 V 17.0 V
Mode of operation of the dynamic braking
Chopper resistor
B+
B-
=
Chopper
control
. 1 13 ⋅ 2 ⋅ V = . 1 13
line sup ply
⋅
. 0 98 r 1242
is calculated as a function of parameter
DC chopper
0
x
1
1
Alarm
A0535
0
500 - 600 V
21.3 V
3 Functions
~
⋅ 2 ⋅ P 0210
x
t
= ⋅
t
Chopper, ON Chopper
100
141