Inductor Question

[n1mr0d]

Hi, i have a question about a transformer/inductor i am curious about, pictured below. It seems to have 2 coils on a laminated closed U core. The nameplate says 'transformer', but is used as a inductor/reactor. The two coils seem to be connected in series. Does these setup have 'special' characteristics with saturation etc?.

 

[Skogsgurra]

It would help a lot if you showed us the nameplate.

Gunnar Englund

http://www.gke.org

 

[ScottyUK]

Common mode choke?


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Sometimes I only open my mouth to swap feet...

 

[mc5w]

It could be an autotransformer that steps down from 220 or 340 volts end grounded ( such as from a 220Y380 system ) to 110 or 120 volts to power certain kinds of toys in European houses.

For some reason, most areas in Europe use 220Y380 to 240Y416 from the utility to customers and if a customer needs 110 or 120 volts to run bathroom lighting, shavers, hair dryers, and so forth they have to buy a transformer.

Here is the U.S. we stuck with 240 volts center tapped to ground for the utility company transformer secondaries. There are very few houses here is the U.S. that have 3-phase power to run air conditioning. Some of these were built back when household central air had to be 3-phase. Some are million dollar plus houses that use at least $1,000 per month of electricity. The way that noise abatement was done along Interstate 71 in Columbus, Ohio was to run 120/240 4-wire delta 3-phase into all of the houses and stick in 3-phase air conditioners but then in Columbus' armpit climate household central needs to be on 3-phase power.

If you look in the back pages of the GE Blue Book there are some diagrams for using a single form 9A or 16A meter to meter a single phase lighting service and a 240 volt 3-phase power service. One of the early concepts for 240 volt power in houses was to supplement the 120 volt 2-wire service with a 240 volt corner grounded 3-phase service and then use a form 16A or 16S meter to meter both services. The 2 three phase concepts that won out for small commercial or large residential were a single service either 120Y208 volts or 120/240 4-wire delta.

Oh yea, West Penn Power in Pennsylvania will put 3-phase power into a house that has a geothermal heat pump for heating. Different utilities, different policies.

 

[ScottyUK]

For some reason, most areas in Europe use 220Y380 to 240Y416 from the utility to customers and if a customer needs 110 or 120 volts to run bathroom lighting, shavers, hair dryers, and so forth they have to buy a transformer.

No, we just buy 230V lighting, 230V hairdryers, 230V shavers, etc. Amazingly these things are available from European manufacturers and we aren't tied to US imports! Shavers is an interesting one in the UK: in a bathroom location, an isolation transformer is required for a shaver outlet. The secondary of the transformer is usually tapped for 120V and 240V. These are the only socket outlets allowed in a bathroom. The application where 110V is common in the UK is for portable power tools for the industrial environment, where a 55-0-55V centre tap earthed arrangement is used to reduce the risk to the user.

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Sometimes I only open my mouth to swap feet...

 

[n1mr0d]

Guys, like I said it is used as a inductor. I measured the inductance of the device with a Variac and a LCR meter, and it's inductance is ~40mH. Is there any reason it behaves signifcally different from a ideal inductor?

 

[ScottyUK]

Saturation properties are probably the major difference from an ideal inductor. The split winding compared with a single winding shouldn't make too much difference at low frequency, but the high frequency behaviour will be different because of the different interwinding capacitance. It is probably irrelevant because iron-cored inductors aren't typically used at HF. Low frequency inductance should be fairly predictable if the number of turns and the core material properties are known. Check to see if the core has an airgap. This will be hugely significant if the inductor current has a DC bias because it will reduce the probability of saturation.

Can you provide any more information about what function this inductor has in the circuit?


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Sometimes I only open my mouth to swap feet...

 

[edison123]

This is probably used in parallel with capacitive test circuits (like AC HV test kit for generator/motor windings) to reduce the input current.

* How do centenarians handle peer pressure ? *

 

[waross]

It may be a 1:1 isolation transformer, if you seperate the windings, or it may be used as a 2:1 auto transformer to generate an artificial neutral, generate 200% of the supply voltage or generate 50% of the supply voltage.
Another connection which appears to be a series connection when tested with a multi-meter would be a parallel connection with one of the paralleling jumpers removed. This would be similar to an isolation connection with one common line. (Possibly for a common ground.) This would limit the available current to the circuit or equipment that was connected to it.
As skogs pointed out, give us a legible picture of the nameplate and we can probably stop guessing and give you a definite answer.
respectfully