Data Sheet

POWER-NIKKOHM
900W
CHASSIS MOUNTING NON-INDUCTIVE HIGH POWER RESISTORS
TCP900
Pulse Operation
DC/AC rms Operation
RoH
S
Nikkohm Co., Ltd. 3-31-2640 Minamicho, Misawa, Aomori 033-0036 Japan TEL: [phone], FAX: [phone]
© Nikkohm Co., Ltd. URL: http://www.nikkohm.co.jp
& http://www.nikkohm.com / e-mail: [e-mail]
10ns 100ns 1us 10us 100us 1ms 10ms 100ms 1s 10s 100s
Pulse width (duty 0.01)
10,000
1,000
100
10
1
0.1
0.01
Pulse peak power (kW)
Test Method
Dotted: assumption
DUT
TCP900X-50ohmJ
Resistor, resistor temperature, tr
Flange, flange temperature, tf
Heat sink, heat sink temperature, th
A
ir temperature, ta
Resistor generates Joule heat in DC or AC rms
operation at resistor material, and Joule heat shall be
cooled by thermal conduction. Finally, the heat is
transported to the internal air electronics or cooling
liquid, makes a steady state. Then, the temperature of
each portion of a resistor shows a fixed value, as shown
in a right figure.
Accumulated heat resistance between resistor material
and air temperature Rt is,
Rt = Rrf + Rfh + Rha
When applied power shows P
Rrf = (tr-tf)/P…°C/W…….0.10°C/W
Rfh = (tf-th)/P..°C/W…….about 0.01°C/W
Rha= (th-ta)/P..°C/W…depends on size of heat sink.
For example:
When Rha=6.0 ° C/W, ta=50 ° C, max resistor
temperature 155 °C and allowable power P1,
P1=(tr-ta)/Rt=(155-50)/(0.1+0.01+6.0)=17.1W
When Rha=0.1 ° C/W, ta=50 ° C, max resistor
temperature 155 °C and allowable power P2,
P2=(tr-ta)/Rt=(155-50)/(0.1+0.01+0.1)=500W
Please note, when air cool heat sink is used, actually
keeping flange at less than 25 °C is difficult. When
flange temperature is over 25 °C, rating will be
decreased as shown above derating curve.
In DC operation, allowable power depends on a cooling
performance of the heat sink.
Above drawing shows allowable pulse peak power that obtained by actual breaking test of TCP900Z-10ohm-J, and shows the result of
double safety factor. The test was performed by observation of small resistance change after application of continuous pulse, that is
rectangular waveform
and 0.01 duty.
Since the pulse durability is moved by the resistance, the pulse waveforms and type of pulse source, constant voltage source or current
source, please test carefully for long terms on actual electronics when operating the resistor by the pulse of the peak power exceeding rated
power.
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