LPSA800-D-R240JB datasheet(3/6 Pages) VISHAY

3 / 6 page

LPSA 800

www.vishay.com

Vishay Sfernice

Revision: 10-Nov-2021

Document Number: 50078

For technical questions, contact: sferfixedresistors@vishay.com

THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT

ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000

RECOMMENDATIONS FOR MOUNTING ONTO A HEATSINK

• Surfaces in contact must be carefully cleaned.

• The heatsink must have an acceptable flatness: from 0.05 mm to 0.1 mm/100 mm.

• Roughness of the heatsink must be around 6.3 μm. In order to improve thermal conductivity, surfaces in contact (alumina,

heatsink) should be coated with a silicone grease (type Bluesil Past 340 from BlueStar Silicones) or a thermal film (type Q

pad II) easier and faster to install than the grease.

• The fastening of the resistor to the heatsink is under pressure control of two screws tightened at 2 Nm for full power

availability.

• The following accessories are supplied with each product:

- 2 screws CHC M4 x 25 class 8.8 and 2 M4 contact lock washers for heatsink mounting

- 2 screws TH M4 x 6/6 and 2 M4 contact lock washers for connections.

CHOICE OF THE HEATSINK

The user must choose the heatsink according to the working conditions of the component (power, room temperature).

Maximum working temperature must not exceed 175 °C. The dissipated power is simply calculated by the following ratio:

expressed in W

ΔT:

difference between maximum working temperature and room temperature

RTH (j - c): thermal resistance value measured between resistive layer and outer side of the resistor.

It is the thermal resistance of the component: (see specifications environmental paragraph).

RTH (c - h): thermal resistance value measured between outer side of the resistor and upper side of the heatsink.

This is the thermal resistance of the interface (grease, thermal pad), and the quality of the fastening device.

RTH (h - a): thermal resistance of the heatsink.

Example:

RTH (c - a) for LPSA 800 power dissipation 180 W at +50 °C room temperature.

ΔT ≤ 175 °C - 50 °C = 125 °C

RTH (j - c) + RTH (c - h) + RTH (h - a) =

= 0.69 °C/W

RTH (j - c) = 0.112 °C/W

RTH (c - h) + RTH (h - a) = 0.69 °C/W - 0.112 °C/W = 0.578 °C/W

Notes

• Configuration 1: Water cooling heatsink CP15 from Lytron (304 mm x 95.3 mm x 8 mm) with water flow rate 4 LPM and thermal grease

Bluesil Past 340 from BlueStar silicones.

• Configuration 2: Air cooling heatsink P207/250 from Semikron (250 mm x 200 mm x 72 mm) and thermal grease Bluesil Past 340 from

BlueStar silicones.

• Configuration 3: Water cooling heatsink CP15 from Lytron (304 mm x 95.3 mm x 8 mm) with water flow rate 4 LPM and thermal pad

Q-Pad II from Berquist.

• Configuration 4: Air cooling heatsink P207/250 from Semikron (250 mm x 200 mm x 72 mm) and thermal pad Q-Pad II from Berquist.

OVERLOADS

In any case the applied voltage must be lower than UL = 5000 V.

Short time overload: 1.5 x Pr/10 s

Accidental overload: The values indicated on the following graph are applicable to resistors in air or mounted onto a heatsink.

Tightening Torque on Heatsink

LPSA 800

2 Nm

CONFIG. 1:

WATER COOLING

HEATSINK CP15

AND THERMAL GREASE

BLUESIL PAST 340

CONFIG. 2:

AIR COOLING

HEATSINK P207/250

AND THERMAL GREASE

BLUESIL PAST 340

CONFIG. 3:

WATER COOLING

HEATSINK CP15 AND

THERMAL

PAD Q-PAD II

CONFIG. 4:

AIR COOLING

HEATSINK P207/250

AND THERMAL

PAD Q-PAD II

Power dissipation (W)

710

282

307

180

T° resistive element (°C)

175

TH (j - c) max. (°C/W)

0.112

TH (c - h) typ. (°C/W)

0.05

0.13

0.34

0.43

TH (h - a) max. (°C/W)

0.059

0.29

0.059

0.29

Fluid T° (°C)

ΔT

TH (j - c)

TH (c - h)

TH (h - a)

-------------------------------------------------------------------------------------------

ΔT

------

125

180

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