Siemens 420 manual Flying restart active Search direction

Issue 07/04 3 Functions

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 fsearch,max (refer to Fig.

3-54).

fsearch,max = fmax + 2 ⋅ fslip,standard = P1802 + 2 ⋅ r0330100 ⋅ P0310

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).

MICROMASTER 420	Operating Instructions
6SE6400-5AA00-0BP0	129