Post on 20-Feb-2022
transcript
Thermal Design of Automatic Power Factor
Correction Panels
Mudit Bhatia
Importance
• Temperature – A deciding factor of life, especially for capacitors in APFC panels
• For every 10° C increase in temperature, life of the capacitor (any dielectric) reduces to half
• Parameters affecting the internal temperature of the panel :
Ti = Ta + PL.ZTHwhere, Ti : Internal temperature of the panel
Ta : Ambient temperature (around panel)PL : Power loss of components inside the panelZTH : Thermal impedance of the panel (°C / W)
ZTH
PL
Ta
Ti
What are the factors affecting thermal impedance?
No sufficient space provided
around the reactor
1. Panel design related – Poor thermal design
Blocking/ Not providing suitable path for heat flow
Reactor kept near capacitor in
completely enclosed compartment
Insufficient sizing of fans (lower heat flow rate) and/or louvers
Exhaust fans with less CFM
1. Panel design related – Poor thermal design
Louvers
Cooling Fans
PLINTH
Inappropriate location of panel breathers/ fans
Louversimmediately under
exhaust fan
Inappropriate fan mounting
Reduced rate of air
flow, hence,
overheating
1. Panel design related – Poor thermal design
Capacitors kept above
reactors
Reactors kept one above another
Improper positioning of major heat sources inside the panel
Capacitors kept close to
reactors
1. Panel design related – Poor thermal design
2. Site Conditions Related
Dust Choking the breathers
Air velocity measurement through louvers
Choked with dust – no air flow
Air flow after cleaning
• Cooling Fan Failures • Modifications made by the end user, inside the panel after commissioning
Thermistor not connected
2. Site Conditions Related
Leakage through gasket due to aging
Louvers
Cooling Fans
PLINTH
Insufficient space around panels
• Panels kept too close to the walls
• Some objects blocking the bottom / inlet louvers
• Panel room ventilation
2. Site Conditions Related
Recommendations
Reduced rate of air flow,
hence, overheating
Louvers
Cooling Fans
PLINTH
Louvers
Cooling Fans
PLINTH
Use of rails or
perforated plates for mounting
• Decide the cooling method based on the allowed temperature rise
• Proper selection of fan size and number of such fans by doing necessary calculations
• Isolating the heat source with the temperature sensitive components
• The above can be enforced through new standard, which shall be derived through IEC 61439 / IEC 61921
Recommendations for better thermal design
Thank youתודה
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