Bosch rexroth SYDFED 2X Series Manual page 24

24/96 SYDFED-2X, SYDFED-3X, SYHDFED-1X | Product description
Continuous regenerative
operation
Bosch Rexroth AG, Edition 11.2021, RE 30017-B
Zero stroke operation can be definitely achieved only by means of a minimum
command value feedforward in the closed swivel angle control loop.
The feedforward of "0 bar" via the pressure command value branch is not
permitted. This is valid for both, actuating systems with internal and external
supply.
The following is valid when the valve electronics is de-energized:
• Zero stroke operation for the internally supplied pump
• Swiveling out to "-100%" of the externally supplied pump
5.3.4.1 Regenerative operation
Regenerative operation is a special operating mode of the SY(H)DFED control
system, since in this case the SY(H)DFED control system is operated as both,
generator and motor.
We can distinguish between continuous regenerative operation and brief
regenerative operation. In the first case, by this we understand coupling of the
variable displacement pump with a fixed displacement pump. Here, the two pump
displacements are fed together to a common consumer.
This operating mode can be utilized in conjunction with a fixed displacement pump
in order to increase the displacement. To achieve "zero" displacement, the closed-
loop-controlled pump must "take over" the entire flow from the fixed displacement
pump and therefore swivels to the negative swivel angle range (motor operation).
It must be noted here that both pump sizes must be matched to each other so that
the controlled pump (in regenerative operation) must swivel in to max. –70 %. The
fixed displacement pump should be mounted to a through-drive of the
SY(H)DFED control system.
The following pump variants are available for continuous regenerative operation:
0487: Continuous regenerative operation with external supply
0541: Continuous regenerative operation without external supply (for SYDFED-3X
only)
The operating mode "regenerative operation with external supply" is somewhat
complicated in terms of design and commissioning, because a pump swiveling
in too far (e.g. -75 % instead of -70 %) causes cavitation.
We therefore recommend master/slave operation as an alternative with two
closed-loop controlled SY(H)DFED control systems or a pump variant designed
for continuous regenerative operation without external supply (SO 0541 in the
case of SYDFEx-3X).
Continuous operation is possible when the given operating limits are adhered to.
However, at a total displacement of "zero" (that is, at a negative swivel angle of the
SY(H)DFED pump) and at high pressures, the noise level increases and efficiency
deteriorates.
For working points with a negative swivel angle of the control pump,
continuous regenerative operation features a poorer overall efficiency than a
comparable master/slave pump system or a comparable single pump. In the
case of an energy-saving machine, continuous regenerative operation would
reduce the energy-saving effect. A comparable master/slave pump system or a
comparable single pump would provide higher energy savings in such an
application.
For pumps with external supply, the use of a pressure relief and anti-cavitation
valve as shown below in Fig. 7 is indispensable to prevent the pump's running dry.