Siemens MICROMASTER 420 - Manual (Page 129)

Issue 07/04 3 Functions
MICROMASTER 420 Operating Instructions
6SE6400-5AA00-0BP0 129
3.16 Flying restart
Parameter range: P1200
P1202, P1203
r1204, r1205
Warnings -
Faults -
Function chart number: -
The "Flying restart" function (this is enabled using P1200, refer to Table 3-23)
allows the drive inverter to be switched to a motor which is still spinning. If the drive
inverter was to be powered-up without using the flying restart function, there would
be a high possibility that a fault with overcurrent F0001 would occur. The reason for
this is that the flux must first be established in the motor and the V/f control must be
set corresponding to the actual motor speed. The drive inverter frequency is
synchronized with the motor frequency using the flying restart function.
When the drive inverter is normally powered-up it is assumed that the motor is
stationary and the drive inverter accelerates the motor from standstill and the
speed is ramped-up to the setpoint which has been entered. However, in many
cases this condition is not fulfilled. A fan drive is a typical example. When the drive
inverter is powered-down the air flowing through the fan can cause it to rotate in
any direction.
Table 3-23 Settings for parameter P1200
Parameter P1200 Flying restart active Search direction
0 Disabled -
1 Always Start in the direction of the setpoint
2 For line supply on and fault Start in the direction of the setpoint
3 For fault and OFF2 Start in the direction of the setpoint
4 Always Only in the direction of the setpoint
5 For line supply on, fault and OFF2 Only in the direction of the setpoint
6 For fault and OFF2 Only in the direction of the setpoint
Depending on parameter P1200, after the de-magnetizing time has expired P0347,
flying restart is started with the maximum search frequency f
search,max
(refer to Fig.
3-54).
P0310
100
r0330
2 P1802 f 2 f f
standard slip, max max search,
⋅ ⋅ + = ⋅ = +
This is realized either after the line supply returns when the automatic restart
function has been activated or after the last shutdown with the OFF2 command
(pulse inhibit).
V/f characteristic (P1300 < 20):
The search frequency is reduced, as a function of the DC link current with the
search rate which is calculated from parameter P1203. In so doing, the
parameterizable search current P1202 is impressed. If the search frequency is
close to the rotor frequency, the DC link current suddenly changes because the flux
in the motor establishes itself. Once this state has been reached, the search
frequency is kept constant and the output voltage is changed to the voltage value
of the V/f characteristic with the magnetizing time P0346 (refer to Fig. 3-54).