Tag Archives: thermal management

Case Study: PCB Cooling for Telecom Application

PCB Cooling for Telecom

ATS engineers designed a thermal solution for a telecom board, using ATS patented maxiFLOW heat sinks, which met the customer’s thermal requirements. (Advanced Thermal Solutions, Inc.)

Engineers at Advanced Thermal Solutions, Inc. (ATS) were brought into a project to assist a client with cooling a PCB that was going to be installed in telecommunications data center. The board currently had heat sinks embedded with heat pipes covering the two hottest components but the client wanted a more reliable and cost-effective solution.

ATS engineers used the company’s patented maxiFLOW™ heat sinks to replace the heat pipes and through analytical and CFD modeling determined that by switching to maxiFLOW™ the junction temperature and case temperature would be below the maximum allowed.

Challenge: The client had a new PCB over which air could flow from either direction and two of the highest power dissipating components were on opposite sides.

Chips/Components: WinPath 3 and Vector Processor

Analysis: Analytical modeling and CFD simulations determined the junction temperature with air going from left-to-right and right-to-left and ensured it would be lower than the maximum allowable (100°C for one component and 105°C for the other).

Test Data: With air flowing from left-to-right, CFD simulation determined that the junction temperatures would be 89.3°C and 101.4°C – below the maximum temperatures of 100°C and 105°C. With air flowing from right-to-left, the junction temperature of the most power-dissipating component was 100°C, which was right at the maximum, and the second was at 87°C, which was below it.

Solution: The original heat sinks embedded with heat pipes were switched for maxiFLOW™ heat sinks, with their placement offset slightly to create a linear airflow, and the same levels of thermal performance were achieved.

PCB Cooling for Telecom

ATS engineers changed the embedded heat sinks for maxiFLOW™ heat sinks and received the same thermal performance with a more reliable and cost-effective solution. (Advanced Thermal Solutions, Inc.)

Net Result: The client received the required level of cooling in the PCB, regardless of the direction of air flow, and with a more reliable and cost-effective solution than had been previously been in use.

For more information about Advanced Thermal Solutions, Inc. thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.

Case Study: LED Solution for Outdoor Canopy Array

Advanced Thermal Solutions, Inc. (ATS) was approached by a company interested in a new design for an outdoor LED unit that would be installed in gas station canopies. The original unit was bolted together and contained a molded plastic shroud that held the LED array, the PCB, and an extruded aluminum heat sink.

ATS engineers designed an aesthetically pleasing alternative that utilized natural convection cooling, while increasing the number of the LEDs in the array and its power. The engineers met the customer’s budget and thermal performance requirements.

Challenge: Create an outdoor canopy device that would increase the number of LED in the array, increase power to maximum of 120 watts, and increase lumens, while cooling the device through natural convection.

Chip/Component: The device had to hold an LED array and the PCB that powered it.

Analysis: Analytical modeling and CFD simulations determined the optimal fin efficiency to allow air through the device and across the heat sink, the spreading resistance. The weight of the device was also considered, as it would be outside above customers.

Solution: An aesthetically-pleasing, one-piece, casted unit with built-in electronics box for LED array and PCB was created. There was one inch of headroom between the heat sink and the canopy to allow for heat dissipation and the casting would allow heat transfer as well as allow air to flow through the system.

Net Result: The customer was able to add LEDs to the array and increase power. The new unit also simplified the manufacturing process and cut manufacturing costs.

For more information about Advanced Thermal Solutions, Inc. thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.

Industry Developments: Cooling Solar Power Inverters

By Norman Quesnel, Senior Member of Marketing Staff
Advanced Thermal Solutions, Inc.

(This article will be featured in an upcoming issue of Qpedia Thermal e-Magazine, an online publication dedicated to the thermal management of electronics. To get the current issue or to look through the archives, visit http://www.qats.com/Qpedia-Thermal-eMagazine.)

Traveling across the U.S. one will find the widening use of renewable energy systems, including large scale solar and wind farms. The power from these installations is clean, emission-free and relatively low cost. Their own energy sources are free and endless: the wind and the sun.

Wind energy has become a cost-effective power source, competing with installations of coal, gas and nuclear power. So too has solar power, which is the focus of this article.

Solar power is doing more than ever to help meet energy demands for local power and for feeding power back to the electric grid. Today’s U.S. solar installations exceed 3,100 megawatts, enough to power more than 630,000 homes. The price of solar panels has dropped by nearly a third since 2010 and costs continue to fall. Manufacturers in the U.S. are also exporting billions of dollars worth of solar products. [1]

Solar Power Inverters

Figure 1. Wind and Solar Power Installations Share Some Thermal Management Issues with Other Electronics Systems. [2]

Most thermal management issues in solar power systems occur with their inverter systems. Here, the solar-generated DC power is converted to AC for power grids or local use. While these inverter systems can be very efficient, some excess heat must be managed so it doesn’t affect the inverter’s life or performance.

Cooling Solar Energy Inverters

Some solar power systems produce steam to spin turbines and generate electricity. But the more common solar systems are photovoltaic (PV) solar power facilities. In these, solar panels absorb and convert sunlight into electricity with the use of inverters. One or more solar inverters, or PV inverters, converts the sun-sourced, variable DC output of the PV panels into alternating current, AC. This is then fed into a commercial electrical grid or used by a local, off-grid electrical network. AC is the standard used by all commercial appliances, which is why many view inverters as the gateway between the photovoltaic (PV) system and the energy off-taker. [3]

Inverters are standard in PV solar systems whether they’re kW range residential systems to MW sized power plants. Larger installations may use a central inverter or a series of string inverters.

In a central inverter set up, the DC power from multiple solar panel arrays runs to combiner boxes and then to the inverter which converts it to AC. In a string inverter scheme, there are smaller, individual inverters for several panel arrays. The DC power runs directly into a string inverter rather than a combiner box and is converted to AC. While string inverters are used in residential to medium-sized commercial PV systems, central inverters are common to large commercial and utility-scale sites. [4]

Solar Power Inverters

Figure 2. Photovoltaic Solar Panel Installations Can Feature a Central Inverter or a Series of String Inverters. [4]

There are also solar microinverters that convert the DC generated by a single solar module to AC. The output from several microinverters is combined and often fed to the electrical grid. Microinverters are an alternative to conventional string and central solar inverters, which are connected to multiple solar modules or panels of the PV system. The main advantage of microinverters is that small amounts of shading, debris or snow on any one solar module, or even a complete module failure, do not disproportionately reduce the output of the entire array. [5]

Whatever its configuration, the PV inverter determines the amount of AC watts that can be distributed for use, e.g. to a power grid. For example, a PV system comprising 11 kilowatts DC (kWDC) worth of PV modules, connected to a 10-kilowatt AC (kWAC) inverter, will be limited to the inverter’s maximum output of 10 kW. [6]

There is also some power loss in the DC-AC conversion process. At the MW scale this could significantly impact a plant’s capacity (and revenue). But fortunately, inverter technologies have been advancing and expanding. The efficiency of state-of-the-art converters is more than 98 percent.

In addition to converting DC to AC, today’s inverters provide other services to help ensure their systems operate at optimal performance level. These include data monitoring, advanced utility controls, applications and system design engineering. Some inverters provide maximum power point tracking (to maximize power extraction), and anti-islanding protection (automatic shutdown). [7]

Cooling PV Solar Inverters

All inverters generate excess heat, especially utility-scale central inverters. Solar inverters used in the kW range are typically contained in finned metal housings that provide cooling via natural convection. Large-scale PV inverters are typically between 1 and 2 MW and the heat they generate directly correlates with their conversion efficiency. For an example, a 1 MW inverter with 98 percent conversion efficiency is generating about 20 kW of thermal energy. This is enough heat to comfortably warm 10 homes. [8]

Cooling solutions are typically needed inside inverters to protect their IGBT (insulated-gate bipolar transistors) modules. These solid state power semiconductor devices are electronic switches and consist of many devices in parallel. The design of the IGBTs and their cooling systems are among the most important aspects in protecting inverters and improving their conversion efficiency.

Improper IGBT design results in lower efficiency with higher heat exhaust. Cooling this heat requires a more complex and powerful cooling system. Better thermal management for the switching devices is essential to entering the next era of PV inverter efficiency, beyond 99 percent.

The recently-introduced PVS980 1500 VDC outdoor central inverter by ABB is optimized for large multi-megawatt solar power plants. The PVS980 features a self-contained cooling system to ensure outstanding endurance in tough environments with minimal maintenance. The cooling system uses phase transition and thermosiphon technology to prevent external air from entering the critical compartments of the inverter. This reduces the risk of corrosive gases or sand entering the inverter and causing damage. [9]

Solar Power Inverters

Figure 3. The Cooling System in ABB’s PVS980 Outdoor Central Inverter Uses Phase Transition and Thermosiphon Technology. [9]

The PVS980 inverter can operate from below freezing to extreme heat in 100 percent humidity without jeopardizing functionality. With the simplicity of air cooling and with the power density of a liquid cooled inverter, ABB’s inverter has very high total efficiency and low maintenance. There are no fillable liquids, pumps, valves, inhibitors and thus no leaks. All this makes the PVS980 suitable for any outdoor utility-scale PV plant.

Solar Power Inverters

Figure 4. The LV 5 Series Solar Inverter from GE Power Conversion Features a Liquid Cooling System. [10]

Some of the recent advancement in the inverter cooling system, such as an advanced hybrid cooling solution, requires significantly less air-flow in the system without an auxiliary fan power load. This lower load condition allows the inverter to further increase conversion efficiency. [11]

Solar Power Inverters

Figure 5. Outdoor Central Solar Inverter Whose Power Semiconductors, Inductor and Internal Ambient Air are Cooled by a Two-Phase System. [10]

Parker provides utility scale inverters with two-phase refrigerant cooling systems. The have a high efficiency design that integrates proven insulated gate bipolar transistor power conversion and magnetics with Parker cooling technology. No air conditioner is required. Power semiconductors, inductor, and internal ambient are all cooled by the integral two-phase system. Multiple access panels simplify installation and scheduled maintenance. [11]

The small footprint and high reliability of Parker’s outdoor central solar inverter is made possible by an advanced cooling system that uses a non-conductive, non-corrosive liquid to cool critical components. The refrigerant requires only 13 percent of the flow rate of an equivalent water/glycol based system. The cooling system runs efficiently by capitalizing on the tremendous amount of heat that is transferred as the refrigerant vaporizes, then releasing the heat through a condenser. No compressor is needed. Redundant system components allow inverter operation even after loss of a pump or a fan

Solar Power Inverters

Figure 6. IGBTs Mounted on a Cold Plate Inside a Central Solar Inverter. [11]

Compared to air cooling, with Parker’s solar inverter design IGBT temperatures are kept more constant over time. Advanced cooling is used on both the IGBT devices and the high efficiency inductors, as well as with a unique cool door feature that circulates temperature controlled air inside the sealed enclosure. Heat from the coolant loop is removed by an isolated heat exchanger, with no air exchange from the enclosure interior to the outside environment. Heat exchanger fans are variable speed for maximum efficiency. They are designed for redundancy and are monitored for rotation. In the event of a fan or coolant pump malfunction, the inverter will continue to operate, folding back power if necessary. The cooling system is designed for a minimum of maintenance, and there are no air filters to change.

Solar Power Inverters

Figure 7. Fan-less Heat Pipe Cooling is Used Up to 50% Load in This Toshiba 1500VDC PV Inverter. [12]

Another producer of large scale PV inverters is TMEIC (Toshiba Mitsubishi-Electric Industrial Systems Corporation). Their Samurai inverter series has power ratings up to 2700 kW. Each model has an advanced hybrid cooling system that uses heat pipe technology. The heat pipes allow the system to operate up to 50 percent load without turning on fans. The heat pipe cooling uses fewer parts and a slow speed fan. The fan-less mode runs when the inverter is below 50 percent load at 50°C. Natural convection provides the necessary cooling. Cool air enters from the bottom, flows through the heat pip, and hot air is exhausted from the top. [12]


A PV solar power system’s current inverter determines the amount of AC watts that can be distributed for use, e.g. to a power grid. For systems operating in the megawatt output range, the inverters will require some level of thermal management to cool their IGBT systems. Many of these large inverter systems have custom cooling solutions that can differ from each other (e.g. air cooling vs. liquid cooling) but all methods have their origins in cooling electronics other than those found in the solar power industry.

[1] http://www.cleanlineenergy.com/technology/wind-and-solar
[2] http://www.ucsusa.org/our-work/energy/our-energy-choices/our-energy-choices-renewable-energy#.V_bXoeUrJpg
[3] http://www.solarpowerworldonline.com/2013/04/how-do-solar-inverters-work/
[4] http://cenergypower.com/blog/string-vs-central-inverters-choosing-right-inverter/
[5] https://en.wikipedia.org/wiki/Solar_micro-inverter
[6] http://www.solarmango.com/scp/solar-inverter-the-brain-of-a-solar-power-plant/
[7] https://en.wikipedia.org/wiki/Photovoltaic_system
[8] http://www.solarpowerworldonline.com/2015/02/new-age-solar-inverter-conversion-efficiency-99/
[9] http://www.abb.com/cawp/seitp202/db94b0aa1e8655a9c1257fdb0043680e.aspx
[10] http://www.gepowerconversion.com/sites/gepc/files/downloads/Solar_Single_Pages.pdf
[11] http://www.parker.com/literature/Renewable%20Energy/Parker_RenewablesBrochure__NA_7-2_spreads_lr.pdf
[12] https://www.tmeic.com/Repository/Others/Solar_Ware_Samurai_brochure_Rev-T-July2016.pdf

ATS holding webinar on Thermal Management of Medical Electronics

Medical Webinar

DR. Kaveh Azar, founder, CEO and President of Advanced Thermal Solutions, Inc. (ATS), will present a free webinar on “Thermal Management in Medical Electronics” on Dec. 15, 2016.

On Thursday, Jan. 26, Advanced Thermal Solutions, Inc. (ATS) will host a free, online webinar on “Thermal Management of Medical Electronics”. The hour-long webinar will begin at 2:00 p.m. and there will be 30 minutes of question and answer time after its completion.

The webinar will be presented by thermal management expert Dr. Kaveh Azar, the CEO, President and founder of ATS. Dr. Azar will speak about the unique challenges that are present in finding a thermal solution for medical electronics and the importance of including thermal management in the design process.

The object of all thermal management is to ensure that the device junction temperature, the hottest point on a semiconductor, stays below a set limit. While this is true for all electronic systems, medical electronics pose unique thermal challenges that have to be overcome to meet the junction temperature requirements.

Medical electronics could have stringent material selection. For example, copper is a common metal chosen in thermal management, but can cause irritation or a neurodegenerative condition for patients and has to be used carefully. In addition, medical electronics may have spatial constraints, such as forceps that have only 2-4 millimeters of width, which is a constrained space with very little airflow.

Other challenges presented by medical electronics include the need for constant, reliable repeatability; temperature reliability within a range; and in some cases specific FDA requirements.

Dr. Azar will address each of these issues and more. To register for the free webinar on Thursday, Jan. 26, visit http://www.qats.com/Training/Webinars.

Discussion of Thermal Solution for Stratix 10 FPGA

An Advanced Thermal Solutions, Inc. (ATS) client was planning on upgrading an existing board by adding Altera’s high-powered Stratix 10 FPGAs, with estimates of as many as 90 watts of power being dissipated by two of the components and 40 watts from a third. The client was using ATS heat sinks on the original iteration of the board and wanted ATS to test whether or not the same heat sinks would work with higher power demands.

In the end, the original heat sinks proved to be effective and lowered the case temperature below the required maximum. Through a combination of analytical modeling and CFD simulations, ATS was able to demonstrate that the heat sinks would be able to cool the new, more powerful components.

ATS Field Application Engineer Vineet Barot recently spoke with Marketing Director John O’Day and Marketing Communications Specialist Josh Perry about the process he undertook to meet the requirements of the client and to test the heat sinks under these new conditions.

JP: Thanks again for sitting down with us to talk about the project Vineet. What was the challenge that this client presented to us?
VB: They had a previous-generation PCB on which they were using ATS heat sinks, ATS 1634-C2-R1, and they wanted to know if they switched to the next-gen design with three Altera Stratix 10 FPGAs, two of them being relatively high-powered, could they still use the same heat sinks?

Stratix 10 FPGA

The board that was given to ATS engineers to determine whether the original ATS heat sinks would be effective with new, high-powered Stratix 10 FPGA from Altera. (Advanced Thermal Solutions, Inc.)

They don’t even know what the power of the FPGAs is exactly, but they gave us these parameters: 40°C ambient with the junction temperatures to be no more than 100°C. Even though the initial package is capable of going higher, they wanted this limit. That translates to a 90°C case temperature. You have the silicon chip, the actual component with the gates and everything, and you have a package that puts all that together and there’s typically a thermal path that it follows to the lid that has either metal or plastic. So, there’s some amount of temperature lost from the junction to the case.

The resistance is constant so you know for any given power what the max will be. The power that they wanted for FPGAs 1 and 2, which are down at the bottom, was 90 watts, again this is an estimate, and the third one was 40 watts.

JP: How did you get started working towards a solution?
VB: Immediately we tried to identify the worst-case scenario. Overall the board lay-out is pretty well done because you have nice, linear flow. The fans are relatively powerful, lots of good flow going through there. It’s a well-designed board and they wanted to know what we could do with it.

I said, let’s start with the heat sinks that you’re already using, which are the 1634s, and then go from there. Here are the fan specs. They wanted to use the most powerful fan here in this top curve here. This is flow rate versus pressure. The more pressure you have in front of a fan, the slower it can pump out the air and this is the curve that determines that.

Stratix 10 FPGA

Fan operating points on the board, determined by CFD simulations. (Advanced Thermal Solutions, Inc.)

This little area here is sometime called the knee of the fan curve. Let’s say we’re in this area, the flow rate and pressure is relatively linear, so if I increase my pressure, if I put my hand in front of the fan, the flow rate goes down. If I have no pressure, I have my maximum flow rate. If I increase my pressure then the flow rate goes down. What happens in this part, the same thing. In the knee, a slight increase in pressure, so from .59 to .63, reduces the flow rate quite a bit.

Stratix 10 FPGA

CFD simulations showed that the fans were operating in the “knee” where it is hard to judge the impact of pressure changes on flow rate and vice versa. (Advanced Thermal Solutions, Inc.)

So, for a 0.1 difference in flow rate (in cubic meters per second) it took 0.4 inches of water pressure difference, whereas here for a 0.1 difference in flow rate it only took a .04 increase in pressure. That’s why there’s a circle there. It’s a danger area because if you’re in that range it gets harder to predict what the flow will be because any pressure-change, any dust build-up, any change in estimated open area might change your flow rate.

The 1634 is what they were using previously. It’s a copper heat pipe, straight-fin, mounted with a hardware kit and a backing plate that they have. It’s a custom heat sink that we made for them and actually the next –gen, C2-R1, we also made for them for the previous-gen of their board, they originally wanted us to add heat pipes to this copper heat sink, but I took the latest version and said, let’s see what this one will do. For the third heat sink, I went and did some analytical modeling to see what kind of requirement would be needed and I chose one of our off-the-shelf pushPIN™ heat sinks to work because it was 40 watts.

JO: Is the push pin heat sink down flow from the 1634, so it’s getting preheated air?
VB: Yes. This is a pull system, so the air is going out towards the fans.

Stratix 10 FPGA

CFD simulations done with FloTherm, which uses a recto-linear grid. (Advanced Thermal Solutions, Inc.)

This is the CFD modeling that ATS thermal engineer Sridevi Iyengar did in FloTherm. This is a big board. There are a lot of different nodes, a lot of different cells and FloTherm uses recto-linear grids to avoid waviness. You can change the shape of the lines depending on where you need to be. Sri’s also really good at modeling. She was able to turn it around in a day.

Stratix 10 FPGA

Flow vectors at the cut plane, as determined by CFD simulations. (Advanced Thermal Solutions, Inc.)

These are the different fans and she pointed out what the different fan operating curves. Within this curve, she’s able to point out where the different fans are and she’s pointing out that fan 5 is operating around the knee. If you look at all the different fans they all operate around this are, which is not the best area to operate around. You want to operate down here so that you have a lot of flow. If you look at the case temperatures, remember the max was 90°C, we’re at 75°C. We’re 15°C below, 15° margin of error. This was a push pin heat sink on this one up here and 1634s on the high-powered FPGAs down here.

Stratix 10 FPGA

JP: Was there more analysis that you did before deciding the original heat sinks were the solution?
VB: I calculated analytical models using the flow and the fan operating curves from CFD because it’s relatively hard to predict what the flow is going to be. Using that flow and doing a thermal analysis using HSM (heat sink modeling tool), we were within five percent. What Sri simulated with FloTherm was if a copper heat sink with the heat pipe was working super well, let’s try copper without the heat pipe and you can see the temperature increased from 74° to 76°C here, still way under the case temperature. Aluminum with the heat pipe was 77°; aluminum without the heat pipe was 81°, so you’re still under.

Basically there were enough margins for error, so you could go to smaller fans because there’s some concern about operating in the knee region, or you can downgrade the heat sink if the customer wanted. We presented this and they were very happy with the results. They weren’t super worried about operating in the knee region because there’s going to be some other things that might shift the curve a little bit and they didn’t want to downgrade the heat sink because of the power being dissipated.

Stratix 10 FPGA

Final case temperatures determined by CFD simulations and backed up by analytical modeling. (Advanced Thermal Solutions, Inc.)

JO: What were some of the challenges in this design work that surprised you?
VB: The biggest challenges were translating their board into a board that’s workable for CFD. It’s tricky to simplify it without really removing all of the details. We had to decide what are the details that are important that we need to simulate. The single board computer and power supply, this relatively complex looking piece here with the heat sink, and we simplified that into one dummy heat sink to sort of see if it’s going to get too hot. It all comes with it, so we didn’t have to work on it.

The power supply is even harder, so I didn’t put it in there because I didn’t know what power it would be, didn’t know how hot it would be. I put a dummy component in there to make sure it doesn’t affect the air flow too much but that it does have some effect so you can see the pressure drop from it but thermally it’s not going to affect anything.

JO: It really shows that we know how to cool Stratix FPGAs from Altera, we have clear solutions for that both custom and off-the-shelf and that we understand how to model them in two different ways. We can model them with CFD and analytical modeling. We have pretty much a full complement of capabilities when dealing with this technology.

JP: Are there times when we want to create a TLB (thermal load board) or prototype and test this in a wind tunnel or in our lab?
VB: For the most part, customers will do that part themselves. They have the capability, they have the rack and if it’s a thing where they have the fans built into the rack then they can just test it. On a single individual heat sink basis, it’s not necessary because CFD and analytical modeling are so established. You want two independent solutions to make sure you’re in the right ballpark but it’s not something you’re too concerned that the result will be too far off of the theoretical. For another client, for example, we had to make load boards, but even then they did all the testing.

To learn more about Advanced Thermal Solutions, Inc. consulting services, visit https://www.qats.com/consulting or contact ATS at 781.769.2800 or ats-hq@qats.com.