Siemens 6RA70 specifications Rated DC Current, Card Rack Assembly

The power section for the armature and field converters is constructed of isolated thyristor modules for converters rated from 15A to 850A at 460VAC-line voltage. The heat sink in this case is electrically isolated and at ground potential. On converters rated 1180, 1660 and 1680 amperes at 460 VAC, the power section for the armature circuit is constructed using disk thyristors and the heat sinks are at line voltage potential. The housing and terminal covers on power connections provide protection against accidental contact for operators working in the vicinity. All connecting terminals are accessible from the front.

All open and closed-loop drive control and communication functions are performed by two powerful microprocessors. Drive control functions are implemented in the software as program modules that can be "wired up" and changed by parameters.

2.3Rated DC Current:

The rating plate of the 6RA70 power module has 2 rated currents listed on it. The first output rating is a IEC class I ratings and has no bearing on the base drive panel rating. The second rating is the US (NEMA) rating which the Base Drive Panel rating is derived from.

The US (NEMA) rated current allows operation at this rated current followed by an overload of 150% for 60 seconds in a 45°C ambient. The overload can be applied no sooner than every 10 minutes. Base Drive Panels are designed using the US rating which means that fuses, contactors, and terminal blocks are sized for the rated US (NEMA) current.

The IEC class I rating is the maximum current the power module can supply continuously with no overload. Because an overload is not possible the class I rated current is higher than the US rating. The IEC class I rating cannot be used with Base Drive Panels because the Base Drive Panel fuses, contactors, and terminal blocks will be overloaded.

The microprocessor calculates the current I2t value of the power section cyclically to ensure that the thyristors are not damaged in overload operation.

2.4Card Rack Assembly

One of the many features of the 6RA70 is its ability to expand its functionality modularly through the use of adding additional option cards inserted in the internal card rack of the power module. A complete list of the option cards can be found in 6RA70 catalog available from your local Siemens Sales office.

The card rack assembly contains the CUD1 microprocessor board and two additional slots for two full size option cards or four half-size option cards. The back plane of the card rack assembly contains an EEPROM allowing the CUD1 to be replaced without reprogramming of the parameters. Since additional information specific to the individual unit is programmed into the back plane of the card rack assembly (model #, serial #, PIN code, etc..) the card rack assembly should never be interchanged with another unit. If ordering an additional back plane (part # 6RY1703-0GA01) the model and serial number of the power module will be required.

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