DC−bus operation
Basic dimensioning
Motor efficiency
7
l
120
EDS700ACBA EN 5.1
7.5.3 Motor efficiency
For determining the power requirements, you have to consider the shaft power P
shaft
and
the motor efficiency. The motor efficiency can be found under the motor data.
7.5.4 Power loss of devices
When determining the power requirements, the power loss of the devices must be
considered (¶ Tab. 7−4).
7.5.5 Determining the power requirements
For determining the power requirements of the drive system you need to know the rated
power of the motors and their efficiency as well as the power losses of the controllers. The
power requirements are calculated with the following formula:
P
DCtotal
+
ȍ
n
i+1
ȥ
ȡ
Ȣ
ǒ
P
shaft
Ǔ
i
h
i
)
(
P
loss
)
i
Ȧ
ȣ
Ȥ
P
DCtotal
Total power required by the drive system
P
shaft
Rated power of a connected motor
P
loss
Power loss of a controller
h Motor efficiency
i Index variable for device identification
n Number of devices in the drive system
The supplying device must be able to provide the required power that is calculated.
7.5.6 Determining the regenerative power requirements
With the regenerative power supply modules of the "Servo Drives 9400" series, power
regeneration into the AC mains is possible. Use the determined regenerative power for the
dimensioning of the regenerative power supply module.
7.5.7 Cable protection
In case of interferences, the cables have to be adequately protected.
Please consider the following when dimensioning the DC bus for a plant or machine:
ƒ Mains fuses can be used to protect the DC cables if the wiring is designed for 122 %
of the rated fuse current. Otherwise, the cable protection for the DC cables must be
specially determined.
ƒ Select the fuses for the currents resulting from power P
DC100%
. Please observe the
standards and regulations applicable for the particular location and application.
ƒ Fuse the DC−supply modules according to the Technical data on the AC mains side.
ƒ If the DC bus is wired via the terminals +UG/−UG, always select a 2−pole cable
protection.
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