Siemens 420 manual Compound braking

Issue 07/04 3 Functions

3.14.2Compound braking

Parameter range:	P1236
Warnings	-
Faults	-
Function chart number:	-

For compound braking (this is enabled using P1236) DC braking is superimposed with regenerative braking (where the drive regenerates into the line supply as it brakes along a ramp). If the DC link voltage exceeds the compound switch-in threshold VDC-Comp(refer to Fig. 3-53), then a DC current is impressed as a function of P1236. In this case, braking is possible with a controlled motor frequency and minimum regenerative feedback. Effective braking is obtained without having to use additional components by optimizing the ramp-down time (P1121 for OFF1 or when braking from f1 to f2, P1135 for OFF3) and using compound braking P1236.

Compound braking is suitable for:

Horizontal motion (e.g. traversing drives, conveyor belts) Vertical motion (e.g. hoisting gear)

	P1236 = 0			P1236 >0
	Without Compound braking			With Compound braking
 f	f_set	 f		f_set
	f_act			f_act
	t				t
	i	i
	t				t
u		u
DC-link		DC-link
		UDC-Comp
	t				t
		P1254 = 0 :		UDC-Comp = 1.13 ⋅	2 ⋅ P0210
		P1254 ≠	0 :	UDC-Comp= 0.98 ⋅ r1242

Fig. 3-53 Compound braking

The compound braking switch-in threshold VDC-Compis calculated as a function of parameter P1254 (Auto detect VDC switch-on levels) either directly using the line supply voltage P0210 or indirectly using the DC link voltage and r1242 (refer to the formula in Fig. 3-53).

MICROMASTER 420	Operating Instructions
6SE6400-5AA00-0BP0	125