Crown Macro-Tech 602, Macro-Tech 1202 Reference Manual

Macro-Tech
®
602/1202/2402 Power Amplifiers
Page 37
Reference Manual
7 AC Power Draw and
Thermal Dissipation
This section provides detailed information about the
amount of power and current drawn from the AC mains
by the Macro-Tech 602, 1202 and 2402 amplifiers and
the amount of heat produced under various conditions.
The calculations presented here are intended to pro-
vide 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.
• The amplifier efficiency at standard 1-kHz power is
estimated to be 65%.
• Quiescent power draw is 90 watts (an almost negli-
gible amount for full-power calculations).
• Quiescent thermal dissipation equals 105 btu/hr at
90 watts.
• The estimated duty cycles take into account the typi-
cal crest factor for each type of source material.
• Duty cycle of pink noise is 50%.
• Duty cycle of highly compressed rock ‘n’ roll mid-
range 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, short duration paging is 1%.
Here are the equations used to calculate the data pre-
sented in Figures 7.1 through 7.3:
AC Mains Power
Draw (watts)
=
Total output power with all
channels driven (watts)
x
Duty
Cycle
Amplifier Efficiency (.65)
+
Quiescent Power
Draw (watts)
The quiescent power draw of 90 watts is a maximum
value and includes power drawn by the fan. The follow-
ing equation converts power draw in watts to current
draw in amperes:
Current Draw
(amperes)
=
AC Mains Power
Draw (watts)
x
AC Mains
Volta
g
e
Power
Factor
(
.83
)
The power factor of 0.83 is needed to compensate for
the difference in phase between the AC mains voltage
and current. The following equation is used to calculate
thermal dissipation:
Total output power with all
channels driven (watts)
Thermal
Dissipation
(btu/hr)
=
+
Quiescent Power
Draw (watts)
x
Duty
Cycle
Amplifier Efficiency (.65)
()
x
3.415
.35
x
The constant 0.35 is inefficiency (1.00–0.65) and the
factor 3.415 converts watts to btu/hr. Thermal dissipa-
tion in btu is divided by the constant 3.968 to get kcal. If
you plan to measure output power under real-world con-
ditions, the following equation may also be helpful:
Total measured output power
from all channels (watts)
Thermal
Dissipation
(btu/hr)
=
+
Quiescent Power
Draw (watts)
.35
x
Amplifier Efficienc
y
(.65)
()
x
3.415
Fig. 7.1 Macro-Tech 602 Power Draw, Current Draw and
Thermal Dissipation at Various Duty Cycles

Crown Macro-Tech 602, Macro-Tech 1202 Specifications

General

Brand	Crown
Model	Macro-Tech 602, Macro-Tech 1202
Category	Amplifier
Language	English