Table of Contents
Advertisement
O E M FUNCTIONAL SPECIFICATION ULTRASTAR XP (DFHC) SSA MODELS 1.12/2.25 GB - 1.0" H I G H
2.2.2.1 Power Calculation Examples
Note: The following formulas assume all system ops as a 1 block read or write transfer from a random
cylinder while at nominal voltage condition.
Example 1. Calculate the mean 12 volt average current.
If we assume a case of 30 operations/second then to compute the sum of the 12 volt mean currents the
following is done.
+ 1 2 V D C (idle average)
+ 1 2 V D C (seek average) 0.0031 * 30 =
TOTAL
Example 2. Calculate the mean plus 3 sigma 12 volt average current.
To compute the sum of the 12 volt mean current's 1 sigma value assume all the distributions are normal.
Therefore the square root of the sum of the squares calculation applies.
operations/second.
+ 1 2 V D C (idle average)
+ 1 2 V D C (seek average) sqrt(30*((0.0002)**2))=
TOTAL
sqrt((0.02)**2+(.001)**2))=0.02 amps
So the mean plus 3 sigma mean current is 0.50 + 3*0.02 = 0.56 amps
Example 3. Power Calculation.
Nominal idle drive power = (1.23 Amps * 5 Volts) + (0.41 Amps * 12 Volts) =
Nominal R/W drive power at 30 ops/sec = (1.25 Amps * 5 Volts) + (0.50 Amps * 12 Volts) = 12.25
Watts
Mean plus 3 sigma drive power for 30 random R/W operations/second. Assume that the 5 volt and 12 volt
distributions are independent therefore the square root of the sum of the squares applies.
+ 5 V D C (1 sigma power) 0.05 * 5
+ 1 2 V D C (1 sigma power) 0.02 * 12
Total (1 sigma power) sqrt((0.25)**2+(0.24)**2)
Total power
10.8 + 3 * 0.35
Page 22 of 87
USER RESPONSIBLE F O R VERIFYING VERSION A N D COMPLETENESS
mean
0.41 amps
0.09 amps
0.50
amps
IBM Corporation
sigma
0.02 amps
0.001 amps
= 0.25 watts
= 0.24 watts
= 0.35 watts
= 11.9 watts
Assume a case of 30
11.07 Watts
Source filename=POWER
Advertisement
Table of Contents
