IBM C2B 2.25 Brick On Sled carrier 128-pin HPC - Manual (Page 16)

USER 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 SPECIFICATION ULTRASTAR X P (DFHC) SSA M O D E L S 1.12/2.25 GB - 1.0" H I G H
2.2.1.1 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) 0.28 amps
+ 1 2 V D C (seek average) 0.027 * 30 = 0.081 amps
TOTAL 0.361 amps
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.
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
TOTAL sqrt((0.02)**2+(.001)**2))=0.02 amps
So the mean plus 3 sigma mean current is 0.361 + 3*0.02 = 0.42 amps
Example 3. Power Calculation.
Nominal idle drive power = (1.23 Amps * 5 Volts) + (0.28 Amps * 12 Volts) = 9.51 Watts
Nominal R / W drive power at 30 ops/sec = (1.25 Amps * 5 Volts) + (0.361 Amps * 12 Volts) = 10.58
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) = 0.347 watts
Total power 9.13 + 3 * 0.347 = 10.2 watts
3 The current at start is the total 12 volt current required (ie. the motor start current, module current and voice coil
retract current). See Figure 3 on page 20 for typical 12 volt current during spindle motor start.
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