Redundant 24 VDC bulk power is distributed to the CHARM I/O Carrier to power CHARM I/O Cards (CIOCs), CHARMs, and field devices.
Each CHARM I/O Card (CIOC) supplies redundant 6.3 VDC power for 96 CHARMs, the maximum number of CHARMs supported by a redundant CIOC pair. The CIOCs receive redundant 24 VDC power through connectors on the CHARM I/O Carrier. The carrier busses this 24 VDC power to the CHARM Baseplates to provide redundant 24 VDC power to the field circuits.
Some isolated CHARMs may require separate field power from 24 VDC or 120/230 VAC power sources. These CHARMs can be installed in CHARM Terminal Blocks for use as isolated connections to an externally powered field device. The CHARM Terminal Block provides four terminals: circuit power can be connected to one pair of terminals and the field device to the other pair.
For installations with a significant number of isolated CHARMs, the baseplates provide an internal power bus, called the injected power bus, that supports 24 VDC or 120/230 VAC. This bus receives power through the CHARM Address Terminal. Individual CHARMs can connect to this bus by using a CHARM Fused Injected Power Terminal Block rather than a CHARM Terminal Block. Field power is connected once at the CHARM Address Terminal and then bussed to any CHARM installed in a CHARM Fused Injected Power Terminal Block to power the CHARM's field circuits. A pair of terminals on the CHARM Fused Injected Power Terminal Block connect to the field device.
In most cases, removing a CHARM from the CHARM baseplate removes power from any connected field device. However, CHARM type, terminal block type, and external power distribution can affect whether removing the CHARM removes power from a field device.
Refer to the specification for each CHARM for its input power requirements.