Osborne Transformer Blog

Craft Production is a Good Trick

2009-07-15T21:08:27Z

Image of Harvey Littleton's glass work: Flickr user vigilant20

Some tricks require dedicated practice, persistence, and flexibility. We practice plenty of tricks at Osborne and we're happy to share them. Practicing flexibility is one of the tricks that helps us develop new electromagnetic products.

Often a design will pass through many iterations in the course of becoming a single physical prototype. And complex circuits may require more than one major revision to the first prototype. Insightful changes save a lot of time and expense in the development cycle. It's essential that these ideas come from all members of the production team, because the sooner the good ideas surface, the faster a team can identify and implement opportunities for innovation, the shorter time frame required to reach a stable release. In this way, flexible teamwork during all stages of early development will get your concept to market faster.

]]> While automated production systems have led to efficiencies for many commodity transformer types, the Osborne application specific design approach emphasizes a team oriented "craft manufacturing" process. The creativity and flexibility of the process enables superior quality results and shorter lead times. Financial and quality considerations demand that electromagnetic product designs be developed in a flexible and creative environment.

Please note that different operations analysts use different terms to refer to the same thing. I'm using the term "craft manufacturing" as defined by Wikipedia:

"Craft production (or One-off Production) is the process of manufacturing by hand with or without the aid of tools."

Stevenson's "Operations Management" would classify this process as a "job shop" type:

"A job shop usually operates on a relatively small scale. It is used when a low volume of high-variety goods or services will be needed. [...] High flexibility using general-purpose equipment and skilled workers are important characteristics of a job shop."

The craft manufacturing label is more appropriate than Stevensone's job shop label; our practices at Osborne have developed partially in unison with the "studio glass movement", and artists such as Harvey Littleton, Dominick Labino, and Dale Chihuly.

Craft manufacturing teams tend to be more creative and flexible than teams working with automated production systems. Of course there are exceptions, and at Osborne we favor the advantages of the craft approach. It's the type of work we like to do and it supports close collaboration between engineering and production disciplines. Our craftspeople are not machines! They are skilled technicians and they bring an artisan's attention to detail to every unit. They are also experienced in working with a broad range of electromagnetic products, and this design familiarity helps us identify innovative product opportunities.

Osborne's technicians have a unique combination of skills in the areas of production, engineering, and quality control. The team is alert to the needs of each product as a whole; not just the steps required to move the product through their workstation. Unlike automated production systems, Osborne's technicians are involved in every step of the production process and their skills are not compartmentalized.

The craft manufacturing process allows the production team to contribute to all aspects of design engineering. Creative ideas can occur at every workstation, sometimes very spontaneously. These artisans employ the type of industrial craftsmanship that once characterized the Detroit area. And while many manufacturers have spent decades in pursuit of increasingly automated assembly systems, Osborne's team has focused on handcrafted quality and flexibility. You can be sure those are the types of tricks we'll continue practicing.

Homemade Transformer in California

2009-06-19T23:38:14Z

Image: Flickr user Vintage Roadside

The Wings Lost? Oh.

2009-06-16T22:08:01Z

Image: Flickr user LarsenPhotography

Sure it would have been fun if they won.

The Wings have won a number of titles in recent history. They're very good. It's nice when they win and it's not what you'd call a novel experience for the people of Detroit. The Wings win a lot. They won just last year.

Maybe at times it's more important to look at the economic impact that the games have on the city. Much of that benefit is rightfully retained by the Wings organization, the players, and the owners of Joe Louis Arena. Even so, these grand spectator events help bring a lot of money into town, and some of that money supports local businesses. Spectator sports are a major element in Detroit's economic plan. We can assume that the downtown area's investment in sporting pays off best during events like the Stanley Cup playoffs. An extra home show in a championship final is nothing to sniff at.

It's unpopular to suggest, but didn't the Team have good reason to lose the game six? It would have been a perfectly rational economic decision for professionals in their position.

A lot of fans are emotionally attached to the outcome of the final game. Let's keep the event in perspective. Spectator sports are elaborate and expensive theater productions. It's naive to deny the occasional tension between financial interests and the ideal of pure sport. Detroit has plenty of idealism, the Team plays with integrity and their championship victories are exciting! Yet they shouldn't be seen as a win at all costs endeavor. In this sense, perhaps we can view their loss as a testament to the professional maturity of the team.

Visualizing the US Electric Grid

2009-06-14T21:06:39Z

Image: NPR

Did you catch the recent NPR story about the US electric grid? NPR created some interesting online content to accompany the story - check it out:

NPR's Visualizing the US Grid.

Some details caught my attention:

Less coal. Large sections of the US are powered by less than 30% coal. In other words, many populous and energy hungry states have proven that coal is not as essential for economic growth as coal politics might lead you to think.

Nuclear states. Vermont (71%) and South Carolina (52%) are the only two states with over 50% nuclear.

Gas states. Top 5 Gas states: Alaska (57%), Texas (49%), California (47%), Louisiana (47%), Nevada (47%).

Hydro states. Hydro is dominant in the Pacific Northwest; second only to coal in Montana.

Oil states. 79% of Hawaii's electricity is generated with oil. Florida (17%) and New York (16%) also use oil. Otherwise the national average is 1% or less of each state's grid portfolio.

Solar states. Advances in solar technology are making PV a more viable option across the country, even in states with relatively low average irradiance. Impressive the degree to which high insolation states (Arizona, Nevada, New Mexico) dominate the solar map (compare: 2004 solar radiation map).

Wind technology. Wind speed capacity map suggests that we should look forward to a hugely disruptive design breakthrough in wind generating technology. Perhaps it'll be a variation on the high altitude approach?

Distributed generation. Are the states without any massive scale generation facilities better prepared to transition their grid in the direction of more distributed generation? Do they have a technological advantage in terms of managing a major increase in productive nodes?

Five Life Cycle Stages of Transformers and Inductors

2009-06-14T20:55:42Z

Image: Flickr user Graffiti Land

The US EPA http://www.epa.gov/dfe/pubs/wire-cable/wirecable-factsheet.pdf life cycle factsheet for wire and cable outlines the four following stages for Life Cycle Assessment (LCA):

* Raw material extraction or acquisition and material processing;
* Product manufacture;
* Product use/maintenance; and
* End-of-life disposition.

When dealing with transformers and inductors, we find it helpful to call attention to an additional stage:

* Re-manufacturing/downcycling

The re-manufacturing/downcycling stage fits into the chronology after Product use/maintenance and before End-of-life disposition. It's important for designers to be aware of the re-manufacturing/downcycling stage early in the product development process.

Copper Winding or Aluminum?

2009-05-20T00:43:28Z

Image: Flickr user Athena's Armoury

What factors do engineers consider when they specify aluminum or copper windings?

A high percentage of low voltage transformers rated 15 KVA or larger use aluminum windings. Osborne's utility industry clients report that nearly all new service entrance connections at commercial industrial facilities use aluminum conductors. The technology has become commonplace over the past 30 years. Price is an important factor in the rise in popularity of aluminum.

Aluminum commodity prices have been lower than copper in recent years. The result is that aluminum windings have an economic advantage for many applications.

Engineers should not allow raw material costs to overshadow other important points of comparison such as circuit performance and energy efficiency.

More points to consider:

Characteristic:	Aluminum	Copper
Thermal Conductivity:	0.57 (Cal/s-cm-K)	0.94 (Cal/s-cm-K)
Electrical Resistivity:	2.69 (X 10^8, Ohm-m)	1.673 (X 10^8, Ohm-m)
Coefficient of Expansion:	23.5 (X 10^6, 1/Deg.C)	17.0 (X 10^6, 1/Deg.C)
Tensile Strength	12,000 (lb/in)^2	32,000 (lb/in)^2

Source: "Electronic Engineers Handbook", Donald G. Fink, McGraw-Hill, 1997.

]]> One additional and important characteristic to consider is size. Aluminum is less conductive than copper, and as a result, aluminum wound transformers need to be designed using larger wire sizes. Larger wire translates to larger diameter coils and greater volume cores. This means an aluminum wound transformer will be bigger than a comparably performing copper wound transformer.

The size advantage of copper wound transformers tends to be immaterial for units rated greater than 15 KVA. This is due to the performance sensitivity that size plays in smaller scale equipment. Machines that require higher power transformers generally have ample space to accommodate the relatively larger size of aluminum wound transformers.

Copper wound coils can deliver similar electromagnetic performance in a smaller physical footprint. This size advantage is beneficial when designing transformers rated below 15KVA.

Michigan Green Jobs Report 2009

2009-05-12T22:42:21Z

Van Jones image from Flickr user andrea.kerbuski.

This week the State of Michigan released a 2009 Green Jobs Report.

Click here to download the report (link at bottom).

The report offers a number of recommendations. Please add remote collaboration to the top of that list. Technology transfers, both into and out of the State, will be essential to a vibrant green economy in Michigan.

There are viable and green economic models emerging in all corners of the US. Additionally, some of the most sophisticated sustainable business practices and experimentation are happening outside the US; most notably in the European Union, Japan, and Australia.

Michigan's green economy will grow along with the global green economy. With investment in remote collaboration technologies, Michigan can become a vital source and destination for the best green innovations.

Mission Motors Electric Performance

2009-05-07T19:06:35Z

The thrill of rapid acceleration is an experience that gets in your blood; and once it's there, it's tough to shake. I'm talking about a neurological sequence, changes in your biochemical system, changes that trigger an unmatched rush of excitement, adrenaline, joy.

If you have a taste for this particular self-indulgence, this need for speed, then you need to know about Mission Motors:

An electric motor offers something no gasoline engine can match: over 100 ft-lbs of gut-wrenching torque wherever and whenever you want.

Congratulations to Edward and the rest of the team at Mission Motors! Click on the link and check out their awesome new bike.

Osborne in IndustryWeek's "Energy Issue"

2008-06-17T00:06:28Z

One of Osborne's areas of research and development in the past few years has been in the use of remote collaboration tools. We work with Socialtext hosted workspaces for internal and external project management. Recently Jeff Osborne gave a brief tour of Osborne's workspaces to Jeff Brainard (then of Socialtext) and Brad Kenney (IndustryWeek). Brad produced two interesting articles on the topic. One article is an overview of performance metrics related to wiki use The next article is a more in depth story about Osborne's history of working with Socialtext. In Brad's words:

"The result has been the gradual creation of a culture of empowerment and accountability, wherein Osborne's workforce adapts this cutting-edge tool to fit needs both old and new."

Thanks Brad!

Alpha Version of Spec Tool

2007-01-05T12:57:07Z

Have you tried the spec tool yet? It´s pretty fun. Check it out.

Our programmers are calling this the alpha version of the spec tool. We think it´s good enough to share and we know there are some bugs. You´re invited to help direct the process of improving the tool. Please share any fixes or features that you´d like to see. We´ll continue to rely on your opinions to guide future tool upgrades. Thanks for sharing your thoughts.

Reduced Duty Cycle Transformer Designs

2007-01-05T05:08:02Z

Image: Flickr user Toni F.

Designing transformers to take advantage of low duty cycle applications can save on physical size and potentially reduce the initial hardware investment. But this approach can quickly lead to component failures and loss of investment, particularly in cases when the specifying engineer miscalculates duty cycle.

1.) On-Off cycle must be considerably shorter than the thermal time constant of the transformer.

Thermal time constants for transformers are usually expressed in hours.
A 50 KVA, 100% duty cycle transformer has a thermal time constant of approximately 6-8 hours.
If the On-Off cycle is less than 60 seconds, you can consider taking advantage of the reduced duty cycle approach in such a case.

2.) How to calculate Duty Cycle:

Duty Cycle (As a Percent) = [Cycle On Time / (Cycle On Time + Cycle Off Time)] x 100

Example: On-Time = 6 seconds, Off-Time = 14 seconds, Duty Cycle = [6 / (6 + 14)] x 100 = 30 Percent

3.) How to Calculate Relative KVA size:

Relative KVA size is calculated by multiplying the 100% Duty Cycle KVA size by the square root of the duty cycle.

Example (Single Phase Application):

Duty Cycle = 30.0 Percent
Load during the On-Time = 50 KVA
Therefore, Design KVA = 50 KVA x SQRT(0.300) = 50 x 0.548 = 27.4 KVA Design.

For easy calculation, assume the On-Time load is 100 Volts and 500 Amps (50 KVA).

"Continuous" (100% DC) Design Current is 27.4 KVA / 100 Volts = 274.0 Amps.

A transformer designed to deliver a continuous current of 274.0 will perform well in an application designed to provide 500 Amps, operating at a 30.0 percent duty cycle.

]]> Additional Issues to Consider

If a user is not aware of using a reduced duty cycle transformer, they may inadvertently increase the duty cycle beyond the capability of the transformer. We recently worked on a project involving an induction heating application that had been successfully running a 30 percent duty cycle transformer for many years. Unfortunately the project managers used this prior line as a model when designing a new production line with different specs. The machine user sought to increase productivity by reducing the duty cycle-times and thereby increasing the effective duty cycle. They increased the duty cycle 50 percent, and accidentally destroyed two power supply transformers before eventually identifying the root cause for the failure (duty cycle miscalculation).

Calculations illustrating the impact of the application are:

Duty Cycle: 30 percent, On-time = 6 seconds, Off-time = 14 seconds
"Actual" Duty Cycle: 50 percent, On-time = 6 seconds, Off-time = 6 seconds
Design Equivalent Continuous Current (30% Duty) = 500 x SQRT(0.30) = 274.0 Amps
Actual Equivalent Continuous Current (50% Duty) = 500 x SQRT(0.50) = 353.5 Amps

Since copper losses vary with the square of the current, running a transformer at 353.5 amps rather than 288.5 amps results in increased copper losses by (353.5 / 274.0)^2 = 1.66 times.

By increasing the power dissipated in the transformer windings by 1.66 times (66% increase), the result is typically an significantly overheated transformer. If the design temperature rise is 115 degrees Celsius, and the actual rise is 1.66 x 115 = 191 degrees Celsius, the life of the insulation system is seriously compromised.

A properly designed reduced duty cycle transformer can save size and money. Unfortunately we've seen a number of cases when specifying engineers make costly errors in calculating duty cycle. The results of a miscalculated duty cycle can lead to damaged equipment - effectively wasting more time and money than the engineers had hoped to save in the first place.

New And Improved Website

2006-12-30T20:42:21Z

Welcome to the new and improved Osborne Transformer website. We're very excited about the new look and feel, and in particular we'd like you to check out our new spec tool, which offers you the ability to define characteristics that you're looking for in 17 types of custom transformers and inductors.

Using a Transformer as a Switch

2006-12-30T17:59:17Z

An electrical transformer is an impedance matching device. This is a well-known fact. Here is an interesting application taking advantage of that fact. If you load the secondary of a transformer with zero (0) ohms (short circuit), the impedance looking into the primary is also zero (0) ohms. Conversely, if the load on the secondary of the transformer is infinite ohms (open circuit), the impedance looking into the primary is also infinite ohms.
Now, if you insert the transformer primary in series with any load across a voltage source, you can switch the voltage to the load on and off. If you short the secondary, the voltage source is applied directly to the load since the transformer primary impedance is zero (0) ohms and all the voltage is fully dropped across the load. And, if you open-circuit the secondary, the source voltage is now fully dropped across the infinite primary impedance and zero (0) volts reaches the load.

Unfortunately electrical transformers are not perfect switches because of inefficiencies. The primary and secondary windings have some impedance which is present even when the secondary is short-circuited. Further, for a transformer to function, there is an excitation impedance present which prevents the primary impedance from reaching infinity, even when the secondary is open-circuited.

But, when a designer knows the load impedance, and the actual open-circuit and short-circuit impedance's of the transformer, they can very often use this application to perform as effective switch. A good application for such a switch would be where the actual switching is done in a high-voltage circuit but the recognition of the switching action is required in a low-voltage control circuit. The transformer insulation system will isolate the high-voltage switch from the low-voltage control.

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Interesting Research at MIT

2006-12-29T07:55:55Z

This from a press release type post at Renewableenergyaccess.com:

"Work at MIT's Laboratory for Electromagnetic and Electronic Systems (LEES) holds out the promise of the first technologically significant and economically viable alternative to conventional batteries in more than 200 years."

Saturable Reactors are Magnetic Amplifiers

2006-12-29T05:56:35Z

Saturable reactors are not common electromagnetic components. Here is a brief overview of why saturable reactors are occasionally referred to as magnetic amplifiers.

Saturable reactors are considered magnetic amplifiers because they can use a relatively small amount of DC volt-amps to control the transfer of a significant amount of AC volt-amps. The DC input is referred to as the control.

The relationship between the DC control volt-amps and AC volt-amps is called the amplification factor. The amplification ratio is often expressed as a ratio: output volt-amps divided by the control volt-amps.

]]> Saturable reactors are commonly used to transfer a system voltage to a load through a series impedance division circuit. The saturable reactor is wired in series with the load impedance and the combination is connected across the system voltage. The magnitude of the voltage reaching the load is determined by the ratio of the load impedance to the total series impedance (load + reactor).

By reducing the impedance of the saturable reactor, the load impedance becomes a higher percentage of the total impedance and thus more of the input voltage is dropped (transferred) across the load. Since both the saturable reactor and the load may consist of resistive and reactive components, each device has an impedance that is the vector sum of its resistance and reactance.

The method used to change the impedance of the saturable reactor is to change its inductance, thus its inductive reactance and therefore its impedance. One technique designers can use to produce the appropriate level of inductance is to optimize the permeability of the magnetic core.

With no DC control current present, the permeability of the core is at its highest value and the inductance is therefore at its highest value. An series analysis will reveal the quantity how much of the system voltage reaches the load under this condition. With the application of a DC control current significant enough to saturate the inductance, the impedance of the reactor is reduced to nearly the value of only its resistance. Under this excitation, the greatest value of the system voltage is dropped (transferred) to the load. For the full system voltage to reach the load, the load impedance must be significantly higher than the resistive component of the reactor.

A typical amplification factor for a 10 KVA saturable reactor, requiring 150 Watts of DC control for full output, is 10,000 / 150 = 67.