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Integrated Motor/Drive
Innovative, integrated drive/control system reduces installation cost
Al Presher, Contributing Editor -- Design News, September 25, 2006
The unique design of a combined motor/drive which attaches the drive to the long axis of the motor produces more torque in a smaller package sizes and reduces installation costs.
By mounting a new electronic control for its IndraDrive® Mi flush onto the motor, Bosch Rexroth reduced the total build space required for the motor/drive package by adding only a small amount to the cross sectional profile. Bosch Rexroth representatives say the resulting design requires up to 30 percent less area compared to other integrated systems where the electronics are fitted behind the motor, and over 50 percent less total space compared to a traditional servo system with separate motor and drive packages.
To effectively dissipate heat, Joe Biondo, marketing manager for Bosch Rexroth, says the design uses high-temperature components and collaboration with Bosch Automotive to design the drive package to be more reliable.
Many integrated motor/drive packages place the drive at the end of the motor. But Biondo says the reason not to put the drive at the end of the motor is to enlarge the heat sink area, and allow a longer motor in the same physical area as competitive drive/motor designs, which generates more torque.
"The way the system is designed allows us to have more heat sink capability," says Biondo. "On the design side, we don't have any wearing or moving parts on the drive. There are no fans, relays or electrolytic capacitors which tend to dry out over time and need to be replaced.
A unique feature of the drive is that it uses dc power. Instead of 230 or 460V dc directly into the package, a power supply in the cabinet provides power for up to 15 drives depending on power range requirements and peak torque required. An umbilical cable combines both the dc bus power, as well as a SERCOS-over-copper communications line.
When several IndraDrive® Mi systems are connected in series, wiring costs are reduced further. Instead of two cables running from the control cabinet for each axis, only one cable is required. Each additional axis is daisy-chained to the preceding axis with pre-fabricated connectors. This reduces cabling costs up to 75 percent over conventional solutions.
Four I/O on each motor are connected to the onboard PLC and can be used for probing and homing, as well as general I/O. Two are dedicated inputs and two I/O are configurable as either inputs or outputs and can be used by the PLC as a registration input to maintain web tension or as a counter module. The I/O offers less than two milliseconds update time.
The IndraDrive® Mi units use the first in a planned series of power electronics modules, and covers three motor sizes with holding torques from 2 to 10 Nm and maximum torques from 8 to 34 Nm. Plans to expand the line-up of motor/drives would include additional power electronics to cover applications both in larger and smaller sizes.
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