Hardware Requirements

Here are the requirements listed for the hardware (electronics and power electronics) of the inverter. These are either derived from The Requirements or are dictated by hardware design decisions or software requirements like for computing power. Also features that have no link to other requirements are to be listed here for reference what should or must be implemented in the inverter software.

The schema for requirement IDs is a text tag followed by a "-" sign follow by a number. Numbers start with 4 digits with the section number at the 4th digit. Requirements in the same section all have the same first digit(s) with the last 3 digits increasing with each requirement. E.g. the first section will be "1000" with the first requirement being "1001". The second section is then "2000" with the first requirement in this section beeing "2001" and so on.)

Requirement ID	Description	Status	implements
HARD-1000	Controller requirements
HARD-1001	The controller must have at least 6 ADC inputs. (See Documentation file "block diagram OSSI system")
HARD-1002	The controller must have at least 9 digital outputs, of which 5 should be PWM capable.(See Documentation file "block diagram OSSI system")
HARD-1003	The controller must have at least one communication interface like UART or USB.		OSSI-4005
HARD-1004	There must be a means for the controller software to get information about the current board version. This may be done by setting various input pins or some external memory device.
HARD-2000	Hardware Design Requirements
HARD-2001	The hardware implementation must not use components "without" leads. This means BGA, QFN or similar devices are not allowed. The rationale behind this is that those components can not be soldered by hand for prototyping and also can not be mounted on the same board as power electronics devices because of the restrictions to PCB layout.
HARD-2002	The design should use SMT devices where possible for higher design density. However smaller devices than 0603 package size or 0.5 mm pin spacing are not allowed.
HARD-2003	For a robust design resistors must not be used with more than 50% of their rated power dissipation.
HARD-2004	For a robust design the use of tantalum capacitors is not allowed. Tantalum capacitors are very sensitive and also have poor durability.
HARD-2005	For a robust design electrolytic capacitors should be rated 200% of the necessary capacity due to aging effects (loss of capacity).
HARD-2006	To provide a variety of possible connection means the connection for AC and DC to the board should be designed to allow for terminals with screws, cage clamps or even ring cable lugs (for nut and bolt connection).
HARD-3000	Insulation Requirements
HARD-3001	The spacing between positive and negative DC input must not be less than 3.5 mm for an input voltage of up to 600 VDC.		OSSI-2003
HARD-3002	The spacing between any DC input and any AC output potential must not be less than 5.5 mm.		OSSI-2003, OSSI-3003
HARD-3003	The spacing between any AC potential on the output side must not be less than 5.5 mm.		OSSI-3003
HARD-3004	The spacing between any DC input and any internal AC potential (not directly connected to grid) must not be less than 3.9 mm.		OSSI-2003, OSSI-3003
HARD-3005	If there is a communication interface the spacing between nets of this circuit to all other potentials must not be less than 6.6 mm (safe insulation).		OSSI-2003, OSSI-3003
HARD-4000	Safety Requirements
HARD-4001	The connection to the grid must be done with two separate relays which are controlled by two separate outputs from the controller. Rationale: If the contacts of one relay are stuck the connection to the grid can still be opened. The same is true if one output of the controller may fail to "always on".