Calculatioin of heater selection

Weekly Note 10W20: Heat Loss of Cabinet

When we use a cabinet in a low temperature environment, we may need a
heater in the cabinet.
How big the power of the heater should be?
Two factors:
1. delta temperature between inner cabinet and environment.
2. the surface area of cabinet
Use the formula bellow:

Q=k*A*dT
k: materials heat loss index, for steel and stainless steel, k=5.5
A: surface area of cabinet
dT: delta temperature between env and inner cabinet.(`C)

So for example, when we use cabinet RITTAL WM483614 with stainless steel
surface and size 1.22x0.91x0.41m, used in -40`C lowest.
Q=5.5*2*(1.22*0.91+0.91*0.41+0.41*1.22)*40=11*(1.1102+0.3731+0.5002)*40=
872.74W

Oh, so big power...note that we ignore the heat power of the electric
components in the cabinet.

Weekly blog_10W21: thermal resistance calculation

2 power module output for redundancy, the easiest way is using the diodes.
But the diodes have about 0.8V forward voltage. So for big current, use MOSFET, for example:
STV300NH02L+LTC4352IMS
This can take low to 0.8mohm resistance.

Even this, the power of the chip can rise to 1.28W under 40A current, we should use the thermal pad for heat dissipating.

How to calculate the Rth?(thermal resistant 热阻)
Rth=H/(Tc*A)
热阻(`C/W)=厚度/(导热系数*面积)
导热系数单位：W/m.k

For example:
CHIP STV300H02L, Rthj-case=0.5`C/W, Rthj-amb=50`C/W
Because we use thermal pad between chip and heat sink, so, we will use Rth-case only. And if use no thermal pad, the heat will dissipate to air directly, Rthj-amb will be used.
Rthj-case, junction到case的热阻，用于case外面有其他导热材料，需将导热材料的热阻相加。。。Rthj-amb，junction到ambient的热阻，就是指到片子周围的环境的热阻，相当于直接向空气传热，如果无其他导热材料，用此参数计算芯片温升。

We select thermal pad: T-global H48-6, Tc=3.2W/m.k, 37x27x5mm, and assume that the heat sink is ideal.
Rth-all=Rthj-case+Rth-pad=0.5+5E-3/(3.2*37E-3*27E-3)=2.64`C/W

Note that this result is very ideal because we assume that the heat to heat sink will be totally dissipated immediately.
Also, the thermal compound can be used too and the calculate method is similar.

热损耗计算_Heat Loss in Cabinet

When we use a cabinet in a low temperature environment, we may need a heater in the cabinet.
How big the power of the heater should be?
Two factors:
1. delta temperature between inner cabinet and environment.
2. the surface area of cabinet
Use the formula bellow:

Q=k*A*dT
k: materials heat loss index, for steel and stainless steel, k=5.5
A: surface area of cabinet
dT: delta temperature between env and inner cabinet.(`C)

So for example, when we use cabinet RITTAL WM483614 with stainless steel surface and size 1.22x0.91x0.41m, used in -40`C lowest.
Q=5.5*2*(1.22*0.91+0.91*0.41+0.41*1.22)*40=11*(1.1102+0.3731+0.5002)*40=872.74W

Oh, so big power…note that we ignore the heat power of the electric components in the cabinet.

Good luck.

NERC CIP

NERC Critical Infrastructure Protection(CIP)-001 is one of 14 standards
set by the North Amerian Electric Reliability Corporation(NERC) to
ensure the reliability and security of the Bulk Electric System.
NERC has regulatory authority over power utilities operating on the Bulk
Power System in the Unit States, Canada, and regions of Mexico.
The purpose of CIP-001 is to ensure all disturbances and unusual
occurrences are reported appropriately.

CIP-001 Sabotage Reporting
CIP-002 Critical Cyber Asset Identification
CIP-003 Security Management Controls
CIP-004 Personnel and Training
CIP-005 Electronic Security Perimeter
CIP-006 Physical Security
CIP-007 Systems Security Management
CIP-008 Incident Reporting & Response Planning
CIP-009 Recovery Plans for Critical Cyber Assets