U S E R RESPONSIBLE F O R V E R I F Y I N G VERSION A N D COMPLETENESS
O E M F U N C T I O N A L S P E C I F I C A T I O N U L T R A S T A R X P ( D F H C ) SSA M O D E L S 1.12/2.25 G B - 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.
| mean |
|
+ 1 2 V D C (idle average) | 0.41 | amps |
+ 1 2 V D C (seek average) 0.0031 * 30 = | 0.09 | amps |
T O T A L | 0.50 | amps |
Example 2. Calculate the mean plus 3 sigma 12 volt average current.
T o 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. Assume a case of 30 operations/second.
|
| sigma |
|
+ 1 2 V D C (idle average) | 0.02 | amps | |
+ 1 2 V D C (seek average) sqrt(30*((0.0002)**2))= | 0.001 | amps | |
T O T A L | 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) = 11.07 Watts |
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 | = | 0.25 watts | ||
+ 1 2 V D C (1 sigma power) | 0.02 * 12 | = | 0.24 | watts | |
Total (1 sigma power) sqrt((0.25)**2+(0.24)**2) | = | 0.35 watts | |||
Total power | 10.8 + | 3 * 0.35 | = | 11.9 | watts |
Page 22 of 87 | I B M Corporation |
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