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Technical data
4
Manual SD6
4.10.5
Projecting
Charging capacity
The charging circuit integrated into a drive controller is also able to charge the
DC intermediate circuit of other drive controllers in addition to its own DC
intermediate circuit.
During projecting of a Quick DC-Link, make certain that the total of the charging
capacities of the drive controllers that are supplied with power is greater than
or equal to the total of the charging capacity of the entire compound DC link
system.
Checking the charging capacity of drive controllers supplied with power –
example
Two drive controllers type SD6A26 that are supplied with power should be able
to charge six type SD6A04 drive controllers. Calculate the maximum charging
capacity of the two drive controllers that are supplied with power as follows:
2 x 1405 µF = 2810 µF.
The DC link circuit capacity in the system to be charged is:
2 x 1000 µF (SD6A26) + 6 x 135 µF (SD6A04) = 2810 µF.
It is therefore equal to the maximum charging capacity.
Quick DC-Link is permissible in this case.
Current-carrying capacity of the input rectifier
When designing the Quick DC-Link, make certain that the total required mains
current does not exceed the maximum mains current.
To calculate both the effective and the maximum mains current, SERVOsoft
®
may be required as mechanical and electrical design software for drive
systems.
Calculating the mains current for motors
The required drive power can be used to determine the mains current for
motors:
Calculating motor power and voltage
The following formulas and assumptions apply when calculating motor power
and voltage:
In addition, the field weakening range also begins.
The effective factor of a servo motor (cos
φ
Motor
) is about 0.9 when operating
at 4 kHz and about 0.98 when operating at 8 kHz. The effective factor of an
asynchronous motor can be determined based on the relevant electrical data.
The following rule applies to the power factor of the mains power supply:
To be able to determine the required mains current and the sizes of the drive
controllers to be supplied with power in the context of Quick DC-Link, the
required motor power must be calculated.
The total maximum permitted input current I
mains,max
is derived from the total
of the maximum input currents I
mains,max
of all connected drive controllers in
continuous operation.
I
mains required
I
mains max
P
mains
P
motor concurrent
P
motor
3 U
motor
I
motor
motor
cos
=
P
mains
3 U
mains
I
mains required
mains
=
U
motor max
0 8
U
mains
=
I
mains required
U
motor
U
mains
------------------
I
motor
motor
cos
mains
---------------------------
=
mains
0 6
I
mains
40A
=
mains
0 7
I
mains
40A
=