Ac Power Draw And Thermal Dissipation - Crown Micro-Tech 1200 Operation Manual

Micro-Tech Series Power Amplifiers
9 AC Power Draw and
Thermal Dissipation
This section provides detailed information
about the amount of power and current drawn
from the AC mains by Micro-Tech amplifiers
and the amount of heat produced under various
conditions. The calculations presented here are
intended to provide a realistic and reliable
depiction of the amplifiers. The following
assumptions or approximations were made:
• The amplifier's available channels are loaded,
and full power is being delivered.
• Amplifier efficiency at standard 1 kHz power
is estimated to be 65%.
• Typical quiescent power draw for the Micro-
Tech 600 is 65 watts; typical quiescent power
draw for the Micro-Tech 1200 and 2400 is 80
watts.
• Quiescent thermal dissipation equals 222
btu/hr at 65 watts and 273 btu/hr at 80 watts.
• The estimated duty cycles take into account
the typical crest factor for each type of source
material.
• Duty cycle of pink noise is 50%.
• Duty cycle of highly compressed rock 'n' roll
midrange is 40%.
• Duty cycle of rock 'n' roll is 30%.
• Duty cycle of background music is 20%.
• Duty cycle of continuous speech is 10%.
• Duty cycle of infrequent paging is 1%.
Operation Manual
Here are the equations used to calculate the
data presented in Figures 9.1, 9.2 and 9.3:
Total output power with all
channels driven (watts)
AC Mains Power
=
Draw (watts)
Amplifier Efficiency (.65)
The quiescent power draw figures provided in
the opposite column are typical and include
power drawn by the fan. The following equation
converts power draw in watts to current draw in
amperes:
AC Mains Power
Draw (watts)
Current Draw
=
(amperes)
AC Mains
x
Voltage
The power factor of 0.83 is needed to compen-
sate for the difference in phase between the AC
mains voltage and current. The following equa-
tion is used to calculate thermal dissipation:
(
Total output power with all x Duty
Thermal
x
channels driven (watts) Cycle
Dissipation =
(btu/hr) Amplifier Efficiency (.65)
The constant 0.35 is inefficiency (1.00–0.65)
and the factor 3.415 converts watts to btu/hr.
Thermal dissipation in btu is divided by the
constant 3.968 to get kcal. If you plan to mea-
sure output power under real-world conditions,
the following equation may also be helpful:
(
Total measured output power
Thermal
x .35
from all channels (watts)
Dissipation =
(btu/hr) Amplifier Efficiency (.65)
x Duty
Cycle
+ Quiescent Power
Draw (watts)
Power
Factor (.83)
)
.35
Quiescent Power
x 3.415
+
Draw (watts)
)
Quiescent Power
x 3.415
+ Draw (watts)
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