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Electric Cars are here, but what about charging them?

18/4/2011

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As electrically powered cars are made available and we read reports about many more being close to production, debates are still raging about a common standard for the plugs they use for charging.

Isn't there already a standard?

Back in 2001, SAE International proposed a standard for a conductive coupler which was approved by the California Air Resources Board for electric vehicle charging stations. The connector has five pins for the two AC wires, with ground and signal pins that are compatible with IEC 61851-2001/SAE J1772-2001 for proximity detection and control pilot function.

The SAE J1772, known as Type 1, is now considered the North American standard for electrical connectors for electric vehicles; and is compatible with numerous vehicles already on the market such as the Nissan LEAF, Chevrolet Volt, Toyota Prius Plug-in Hybrid, Honda Fit EV and the Ford Focus EV.

However, the plug standardization in Europe is part of a process that also includes smart grid elements and battery recharge electronics for cars. In this area there are two broad competing standards.

International competition

German connector manufacturer Mennekes has developed a series of 60309-based connectors enhanced with additional signal pins known as CEEplus connectors, which have been used to charge electric cars since the 1990s. When Volkswagen promoted its plans for electric mobility, Mennekes contacted the company about its requirements for connectors.

In 2008, it derived a new connector, known as Type 2, with utility RWE and car maker Daimler, and this was accepted as the standard connector by other car makers and utilities for field tests in Europe.

The connector has received criticism however, with car manufacturer Peugeot comparing it to the IEC 60309 plugs that are readily available. As such, a number of field tests in France and the UK have adopted the campground sockets that are already installed in many outdoor locations.
 
In 2010, the EV Plug Alliance was formed between electrical companies in France and Italy. Together they created a new connector, known as Type 3, which provides three-phase charging up to 32 Ampere and uses shutters over the socket side pins which is required in 12 European countries but is not included in any other electric vehicle charger plug. Limiting the plugs to 32 Ampere also allows for cheaper plugs and installation costs.

According to the EV Plug Alliance, instead of having a single plug type at both ends of the charger cable, it would be better to choose the best type for each side - its plug is considered the best option for the charger side/wall box leaving the choice for the car side open.

So which option is best?

An ACEA position paper published in June 2010 ruled out a Type 1 connector because of the three-phase charging which is so popular in Europe and China - however, debates remain about whether Type 2 or Type 3 should get the nod as the new industry standard across the continent.

Much of the debate revolves around the shutters used in Type 3 that are absent from Type 2. One argument is that mode three requires the socket to be dead when there is no vehicle attached so there is no hazard that the shutter needs to provide protection from and so the shutters only have advantages in mode two (when the electric car is connected to the supply network not exceeding 32A), allowing for a simpler charging station.

However, a public charging station would expose the charging socket and plugs to a harsher environment and so it is argued that the shutter could easily have a malfunction that is not noticed by the driver.

As such it is expected that the ACEA will adopt Type 2 mode three chargers, which means the charging socket is dead if no vehicle is present. Analysts expect them to be used in home chargers after 2017 while still allowing mode two charging with established plug types that are already available.

Whatever the decision on standardization is, it needs to happen fast. Otherwise the car will be available but with nowhere to charge them except at home.

This all reminds me of just how long it took Cat 6 to get ratified, which was just far too long. The only good thing then was that we had Cat 5e to fall back on. Unfortunately for the environment regarding electric vehicles we have carbon monoxide producing engines to fall back on.
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Ten things to consider when choosing a coax connector

11/4/2011

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In my previous Blog "Coaxial Connector Guide" I gave you a comprehensive guide to common connector types.  I have been asked since to give a bit more information about the type of information you need to help choose the connector that is right for your application.

Here is my top 10 things to consider when choosing the coax connector.

1. Frequency of Operation
Frequency refers to the number of times a periodic action occurs in one second. The SI unit for measuring frequency is hertz. RF connectors are grouped into families, or series. Each series is designed to operate in a frequency range. SMA connectors are an ideal connector for many applications due to its wide frequency range of 0-18 GHz.

2. Characteristic Impedance
Impedance matching is a crucial consideration in the designing process. The SI unit for measuring impedance is Ohms. Most connectors operate between 50-95 ohms. RF connectors used in audio and video applications, such as BNC and F connectors usually operate at 75 ohms. Most 2400 MHz applications operate at 50 ohms.

3. Insertion Loss
Insertion loss, expressed as a ratio in dB relative to the transmitted signal power, refers to the amount of signal power lost in transmission due to device interference. Insertion loss is commonly referred to as attenuation. The farther the signal must travel, the higher the attenuation. Many factors affect insertion loss including coax cable type and length. The ultimate goal of any RF connector is to minimize attenuation.

If the power transmitted by the source is PT and the power received by the load is PR, then the insertion loss in dB is given by:

4. Power Handling
Most RF connectors used in the telecommunications industry safely operate up to 500 volts. Usually the larger the connector, the higher the power handling. For instance, N Type connectors can handle up to 2,700 volts.

5. Gender
In the world of RF connectors, plugs are typically referred to as "male" and are threaded on the inside. Jacks are usually "female" and contain threads on the outside. Not all RF connectors are threaded. MCX connectors utilize a snap on mating mechanism. A good rule of thumb is that plugs house the contact pin.   Except for Reverse Polarity Connectors that have a Mae body and female centre contact, most commonly used in wireless network systems.

6. Form Factor
Since the development of the first UHF connector in the 1930's, Coax connectors have been getting smaller. The micro-miniature IPX connector boasts a profile of only 2.5mm! Keep in mind however; there is a trade-off between size and power handling.

7. Durability
Many factors influence the ruggedness of an RF connector. How often will the connector be connected and disconnected? Most RF connectors are rated up to 500 mating cycles. Is the connector for outdoor or indoor use? At what temperatures will the connector be subjected to?

8. Environmental Considerations
The main factors to keep in mind concerning durability involve environmental considerations. Mil-Spec RF connectors undergo testing standards which simulate environmental conditions such as vibration and corrosion. These standards are usually expressed in MIL-STD-XXX format.

9. Coupling Style
The mating mechanism associated with an RF Connector is another one of the factors concerning durability. The common threaded interface provides a secure connection for SMA connectors, but is not convenient for frequent disconnects as the bayonet locking feature of the BNC connector. Snap on mating is becoming more common in more space critical applications.  

10. Cost
Most often, despite finding the perfect Coax connector for your RF application, the final decision comes down to budget. SMC and SMB connectors are on the higher end of the price spectrum , while F and BNC connectors remain on the lower end.

These considerations serve as a reference summary of top considerations when choosing a coax connector for your application. Trade off's often occur between these factors. However, each project demands its own set of requirements. Decide what works best for YOUR project.

Or talk to your friendly cable assembler who will be happy to help!
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    Hi Nick here! I have been working in Cable Assembly & Manufacturing for a number of years (too many to mention).  You’ll discover I've got a lot to say!   I hope to make your day better and will give some useful info along the way.

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