Datasheet LPSA 800 (Vishay) - 3

LPSA 800
www.vishay.com Vishay Sfernice
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. LPSA 800
Tightening Torque on Heatsink
2 Nm • 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: T P = ---------------------------------------------- R + R + R TH (j - c) TH (c - h) TH (h - a) P: Expressed in W T: 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. T  175 °C - 50 °C = 125 °C T 125 RTH (j - c) + RTH (c - h) + RTH (h - a) = ----- = ------- = 0.69 °C/W P 180 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
CONFIG. 1: CONFIG. 2: CONFIG. 3: CONFIG. 4: WATER COOLING AIR COOLING WATER COOLING AIR COOLING HEATSINK CP15 HEATSINK P207/250 HEATSINK CP15 AND HEATSINK P207/250 AND THERMAL GREASE AND THERMAL GREASE THERMAL AND THERMAL BLUESIL PAST 340 BLUESIL PAST 340 PAD Q-PAD II PAD Q-PAD II
Power dissipation (W) 710 282 307 180 T° resistive element (°C) 175 175 175 175 RTH (j - c) max. (°C/W) 0.112 0.112 0.112 0.112 RTH (c - h) typ. (°C/W) 0.05 0.13 0.34 0.43 RTH (h - a) max. (°C/W) 0.059 0.29 0.059 0.29 Fluid T° (°C) 18 25 18 25
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. Revision: 21-Nov-2019
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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