Sun Microsystems StorageTek 6540, Support Manual

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Chapter 3 Sun StorageTek 6540 Array Installation Requirements 27
* A 240VAC power source is the only recommended source for the 6540 Array.
Calculating Current
Power calculations should use the current ratings at the 240 VAC source. To calculate
for a 1x10, use the current ratings of 2.65 + (10 x 1.95), which equals 22.15 amps.
Each additional expansion tray would add another 2 amps, so a 1x12 takes the
current up to 26 amps. A 1x12 is typically the most that can fit into any one cabinet
(40U of vertical space is required). This means that a 30-amp source from the
customer could safety supply power to one side of the 6540 Array’s trays. The other
side of the trays would need another independent (redundant) 30-amp source to
supply power to the trays, so if any one power source was lost, the 6540 Array
would continue to operate.
If the customer-supplied cabinet has circuit breakers on its PDU or power strip, then
the calculations have to consider the amps drawn by each device plugged in. This
helps to ensure that actual current drawn doesn’t come close to meeting or
exceeding the trip-current. For example a power strip with a 10 amp breaker could
receive 2.65 + 1.95 + 1.95 for approximately 7.7 amps. Remember that current can
vary under certain conditions, so some margin of safety in case the VAC input
voltage drops is required.
Note –
Make sure that the whole array has power supplied to it, and that one source
is not supplying both sides of any one tray.
Single Power Cord and Multiple Cabinet Environments
Customers who are unique cabinet configurations should consult with a certified
electrician. Typically special AC power distribution systems can be provided to
supply power to a 6540 Array.
A single AC power source could be employed, however, as a minimum it may
require the use a 50-amp breaker running 240 VAC. Also internal breakers may have
to employed that don’t exceed 50% of the rating—whether supplying power to one
device or one cabinet. It is recommended that current calculations consider
everything that is plugged into that one line, and not exceed the 50% of the rating.
This is done to protect the 6540 array from losing power during low-voltage
conditions.