Current sense transformers are used to detect and measure current. There are two basic types of products: switch-mode transformers for power conversion applications, and precision-measurement transformers for instrumentation applications. Current sense transformers for power conversion applications are used to measure trends, peak values and average values rather than absolute values. These devices are efficient and dense, but do not offer a great amount of accuracy. They are available in a...
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Q & A on Current Sense Transformers

We asked our users for their input on Current Sense Transformers. Here are the results of 128 users familiar with Current Sense Transformers.

Who Took Our Poll? | Design Trends | Applications and Use | Features | Buying Advice

Who Took Our Poll?Top

Design TrendsTop

Q:
What new technologies are influencing current sense transformer design?
19 answers
Answers:
Use of active amplifiers and Rogowski coils. Smart Grid applications. Changes in Power distribution.
~Jim H, Design Engineer, Castlewood, SD

Well, the built-in rectification in recent models results in AC to DC conversion eliminates profound amounts of labor during installation. This hammers the bottom line down quite a bit and this is great.

~John H, Engineer, Warrenton, VA

Optical current transformer technology is most influencing current transformer design. Due to the almost same accuracy over the entire range of measurement from mA to kA range.

~M.Z.A. S, O&M Personal, Lucknow, India
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Q:
From your perspective, which companies are creating the most innovative current sense transformers?
16 answers
Answers:
Next phase & ABB are involved in most innovative current transformer design.
~M.Z.A. S, O&M Personal, Lucknow, India
Minntronix Inc., Cramer Coil, Coilcraft
~Jim H, Design Engineer, Castlewood, SD

Since current sensing is a proven technology, we can not specify any particular company. There are many players in the market. When package units are considered, you can trust companies like Siemens.

~Ponnuchamy A, Research & Development, Mumbai, India
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Applications and UseTop

Q:
What are some of the applications you have used a current sense transformer for?
34 answers
Answers:

Wide bandwidth true floating voltage measurements. Elimination of ground problems, nearly optimal device. Easier to construct compared to voltage probes. I love them. Not many understand these. Good for hunting noise currents. Limitless uses.

~Max R, Engineering Consultant, Cupertino, CA

AC current measurements in AC induction motors, Auto transformers ,Heaters and rectifier transformers etc. ACCT. DC current measurements in the Silicon controlled rectifiers with DCCT and Shunt etc.

~Ponnuchamy A, Research & Development, Mumbai, India
Qualifying solar thermal hot water heating systems against the real costs of operating grid electric.
~John H, Engineer, Warrenton, VA
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Q:
Please share with us any “non-standard” applications that a current sense transformer has been used for.
10 answers
Answers:

We have developed and are using DCCT to measure DC currents from 0 to 6000 Amps. Development work is in progress to measure 30000 Amps DC. We are also using 8000 Amps ACCT.

~Ponnuchamy A, Research & Development, Mumbai, India
I have used current sensors in motor control feedback loops, but mostly just to monitor energy usage of home and businesses at the breaker panel.
~John H, Engineer, Warrenton, VA

For recording the generator voltage build up characteristics & sudden load throw off characteristics.

~M.Z.A. S, O&M Personal, Lucknow, India
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Q:
Do you know of any disastrous mistakes that occurred due to the incorrect usage of a current sense transformer?
8 answers
Answers:
Forgetting the load resistor is the only issue I know of. Fortunately, many current sense units have this built in or go the next step and rectify.
~John H, Engineer, Warrenton, VA
Leaving CT's connected with no load on the output leads.....very large voltages can develop and cause potential injury.
~Jim H, Design Engineer, Castlewood, SD
Too small gauge wire, high DCR and high temp created.
~Arthur B, Engineering Consultant, Ramona, CA
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FeaturesTop

Q:
What would your design or feature "wish list" be for this product?
23 answers
Answers:

Accuracy over a wide range of DC components. For automotive power seats lumbar motors draw from 0.3 amps nominal, stall at 3.5 amps. The same power wires are monitored for some heater and larger motors where it may go over 20 amps.

~Mark L, Engineer, Hamburg, MI
To end up with a reliable power monitor station for 240 vac power drop from a power line transformer. It must supply a forward/reverse analog signal for power flow direction and amplitude indication. It could be + - 12 v dc.
~Engineer

Plain and simple DC output reflecting the RMS value of the AC Current. Real RMS would be very helpful. Superb galvanic isolation is a must.

~John H, Engineer, Warrenton, VA
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Q:
Is there any advice you want to share with users to help them avoid common errors in selection or usage of a current sense transformer?
10 answers
Answers:

-Always spec your desired end result, such as % accuracy at a rated load across a given temperature and frequency range. -Give the supplier breathing room at both ends of the current range if higher accuracy isn't needed to prevent overly expensive cores. -Ensure you know if there is a linearity requirement along with the accuracy.

~Jim H, Design Engineer, Castlewood, SD
Just pay attention to the max values. Know that surge currents are often greater than the circuit rating. If you need to include surge in your integration, use a sensor that won't cap at the surge rating. Also, keep in mind how your data aq. is loading the sensors output. The measured voltage may be less than you think.
~John H, Engineer, Warrenton, VA

Always specify your application and environment to manufacturer; they can guide you in a better way. Openly discuss with them your problems.

~Ponnuchamy A, Research & Development, Mumbai, India
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Buying AdviceTop

Q:
Do you have any advice for people relative to buying or using current sense transformers?
8 answers
Answers:
At least one set of high accuracy current sensing transformers should be to judge the losses taking place due to non measurable magnetizing current in lower range.
~M.Z.A. S, O&M Personal, Lucknow, India
The design of the interface between the application electronics and the current sense transformers is critical to overall performance.
~Tim C, General Management, Tacoma, WA

If you need a quick response, choose carefully - some of these are designed to monitor loads over a longer time and do not react quickly.

~Mark L, Engineer, Hamburg, MI
Sure, if you have a current transformer without the required load resistor, be prepared to pop one before you know what you are doing.
~John H, Engineer, Warrenton, VA
Make sure your supplier can truly test them across their range and does so in production.
~Jim H, Design Engineer, Castlewood, SD

Always buy from Standard companies as they are with up to date technology.

~Ponnuchamy A, Research & Development, Mumbai, India
Use Rogowski Coils when possible.
~Rodger B, Engineering Consultant, Chesapeake, VA
Safety and accuracy is the key.
~G M, Engineer, Columbia, MD


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