Siemens MICROMASTER 420 - Manual (Page 70)

3 Functions Issue 07/04
MICROMASTER 420 Operating Instructions
70 6SE6400-5AA00-0BP0
3.5.4 Motor data identification (stator resistance)
MICROMASTER has a measuring technique which is used to determine the stator
resistance:
We urgently recommend that the identification routine is carried-out for control-
related reasons. For example, the stator resistance is extremely important for the
voltage boost for the V/f characteristic. The motor data identification routine should
be executed, especially if long feeder cables or if third-party motors are being used.
After selecting the motor data identification using parameter P1910, alarm A0541 is
immediately generated. The motor identification routine is started by the ON
command and different excitation signals are impressed in the motor (DC and AC
voltages). This measurement is carried-out with the motor at a standstill and it
takes, including the data calculation per selection (P1910 = 1) between 20 s ... 4
min. The identification time depends on the motor and increases with its size.
The motor data identification routine must be carried-out with the motor in the cold
condition so that the motor resistance values saved can be assigned to the
parameter of the ambient temperature. Only then is correct temperature adaptation
of the resistances possible during operation.
The motor data identification routine operates with the results of the "Complete
parameterization" P0340 = 1 or the motor equivalent diagram data which was last
saved. The results become increasingly better the more times that the identification
routine is executed (up to 3 times).
WARNING
It is not permissible to carry-out the motor identification routine for loads which
are potentially hazardous (e.g. suspended loads for crane applications). Before
starting the motor data identification routine, the potentially hazardous load
must be secured (e.g. by lowering the load to the floor or clamping the load
using the motor holding brake).
When starting the motor data identification routine, the rotor can move into a
preferred position. This is more significant for larger motors.
NOTE
It is not necessary to lock the motor rotor for the motor data identification
routine. However, if it is possible to lock the motor rotor during the identification
routine (e.g. by closing the motor holding brake), then this should be used to
determine the equivalent circuit diagram data.
The following formula can be applied to check the correctness of the motor
rating plate data:
P
N
= √ 3 ∗ V
N Υ
∗ I
N Υ
∗ cos ϕ ∗ η ≈ √ 3 ∗ V
N ∆
∗ I
N ∆
∗ cos ϕ ∗ η
with P
N
rated motor power
V
N Υ
, V
N ∆
rated motor voltage (star / delta)
I
N Υ
, I
N ∆
rated motor current (star / delta)
cos ϕ power factor
η efficiency