Siemens SINAMICS Series Operating Instructions Manual page 608

Descriptions of functions
10.28 Connecting units in parallel and in series
2. n+m mode in the armature circuit and in the field circuit
In this operating mode, when the master fails the following values are forwarded to the
substitute master:
– the armature firing pulses and the upstream control (setpoint channel, speed control,
– the field firing pulses and the upstream control (EMF control, field current control)
Activation:
On the master and substitute master devices, set p51803 = 2.
Connection:
Outputs 3C and 3D (field DC voltage output) of the master and all substitute masters
must be connected to the motor field winding in parallel.
Remarks on n+n mode:
● When commissioning, after carrying out the optimization (by starting optimization runs, for
example), all parameters set by the optimization runs must be transferred to all substitute
masters according to Chapter "6-pulse parallel connection (Page 603)".
● Since the field supplies are connected in parallel, part of the overall motor-field current
flows through the freewheeling arm of the respective field power units with disabled field
firing pulses. For detecting the total motor field current (displayed at parameter r50035),
in the actual master, the free-wheeling current detected by the "partner" device is
therefore automatically added.
Therefore, for this operating mode, there must be an intact parallel connection as well as
an intact electronic power supply of the master and the substitute master – these are
prerequisites.
If this operating mode is also to be used after the electronic power supply of the master or
the substitute master fails, then the total motor field actual current value must be
externally sensed. The value must be supplied to the master and substitute master using
p50612.
● Generally speaking, the master function is only transferred from the active master to the
substitute master via telegram and an intact parallel interface. Even if the master's
electronic power supply fails, the master still has enough time to transmit a telegram for
the purpose of transferring the master function.
● As soon as the parallel connection is interrupted (by disconnecting the parallel connecting
cable), it can no longer be guaranteed that the master/slave assignment will be correct.
The electronic power supply must be switched off and back on again at all devices!
Note
The control commands – switch-on/stop, operating enable, quick stop, etc. – must also be
entered at all of the substitute master devices.
The speed setpoint and the actual speed value must be entered at all substitute master
devices.
If the thermal overload protection of the DC motor (I
explained in Chapter "Thermal overload protection for the DC motor (I
motor) (Page 582)", the following should be observed:
After a device fails, the calculated motor temperature of this device deviates from the
devices still operational. In this particular case, thermal overload protection as described in
Chapter "Thermal overload protection for the DC motor (I
(Page 582)" no longer applies.
606
armature current control)
t motor monitoring) is used, as
2
t monitoring of the
2
t monitoring of the motor)
2
SINAMICS DCM DC Converter
Operating Instructions, 12/2018, A5E34763375A