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195.228.240.74
In Reply to: RE: Chokes store energy in their magnetic field. posted by Al Sekela on December 13, 2007 at 14:10:19
Are these Hammonds also safe in a 230V network ?
Same inductance (the 193L) suggested for 230V ?
Beside the 5 Henry 193L there are 10 Henry types from Hammond (193M, 193Q).
Which one is the best of above three types ?
Thanks: Ferenc Kolbay
Follow Ups:
I prefer the 193M on the 230v lines. I use a pair of M's on the 230v audio circuit with superb results. I'm not sure what Al is really talking about, I have never experienced any stored energy issues using the chokes on 230v or 120v circuits. The chokes do not react the same way compared to a large a/c transformer, the choke stores almost nothing (64mA for a 120v circuit) when used in parallel to cause any type of problem.
Alan Maher
Not much, but some might see a spark when pulling the plug if they do it often enough and are lucky to hit the peak of the current waveform. Remember the choke is rated for its inductance at a specified DC current. The inductance and stored energy from the AC will be different when the DC current is zero.
Alan, welcome and thanks for the info: Ferenc
It's great to see you back!!
My best wishes to Your and Your's this holiday season and a happy and healthy New Year
Warm Regards
Julien
"There's someone in my head, but it's not me"
where L is inductance and I is the current flowing through the inductor.
Inductance (measured in henries, H) is an effect which results from the magnetic field that forms around a current-carrying conductor. Electrical current through the conductor creates a magnetic flux proportional to the current. A change in this current creates a change in magnetic flux that, in turn, generates an electromotive force (emf) that acts to oppose this change in current. Inductance is a measure of the generated emf for a unit change in current. For example, an inductor with an inductance of 1 henry produces an emf of 1 V when the current through the inductor changes at the rate of 1 ampere per second. The number of turns, the area of each loop/turn, and what it is wrapped around all affect the inductance. For example, the magnetic flux linking these turns can be increased by coiling the conductor around a material with a high permeability.
Stored energy
The energy (measured in joules, in SI) stored by an inductor is equal to the amount of work required to establish the current through the inductor, and therefore the magnetic field.
Inductive Kick
Inductive kick is the unintentional injection of energy into a circuit from the collapsing of the magnetic field in an inductor when its source of power is disconnected.
When a switch opens, the air gap between the two contacts acts like a resistor and tries to prevent current from flowing across the gap. Initially, the air gap is very small and the resistance value is very low. In a very short time, the air gap gets larger and the resistance value increases from 0 to ¥ (infinity). Using Ohm's law across the gap, E = I x R, we get E = I x ¥ = ¥ . This very large voltage value will cause a huge arc across the contacts of the switch and cause the contacts to weld shut or cause electrical fires. This large voltage spike when current is interrupted through a coil is called "inductive kick." Inductive kick is the major contributor to the erosion of the contacts in our switches and circuit breakers. If we consider an opening switch passing through the 100,000 W point, with 10 amps through it we get P = I x R = 10,000,000 watts being dissipated in a very small area. The damage is usually referred to as pitting. In our circuit breakers we use arc chute assemblies to dissipate the arc produced when the breaker opens. Without arc chutes, the arc would be an uncontrolled fire ball.
Inductive kick is precisely how an automobile's ignition system works! The points interrupt the current to the ignition coil, which responds by producing a very large voltage spike that causes an arc across the gap of the spark plug.
Inductive kick may also be the destructive force in many electronics failures that we traditionally have attributed to "unplanned restoration" of power after an electrical casualty. A strong case can be made that the electronic equipment is damaged when circuit breakers trip open while carrying very high currents serving inductive loads. These conditions are often encountered while conducting engineering drills. All electronic equipment bought to MILSPECS is designed with spike suppression circuitry in the power supply to avoid damage from inductive kick. If you suffer an electronics casualty while having circuit breakers tripped under load, do not assume the equipment was damaged due to improper restoration of power, but assume the damage was done on the way down and you should have the designed protective circuitry tested and repaired before further operation.
I remember richard grey used to demo his product by lighting (just a flash) up a 120V bulb from the stored energy in his choke in the parallel product using 1.5V battery as a source. If you look at the spec it said 6000w stored power but it draws less than 5watt of power.
http://www.richardgrayspowercompany.com/specs/600_specs.pdf
That's true, but Dick's choke is designed for a/c and not d/c....the Hammond doesn't come even close to the RGPC specs in that regard.
Alan
Thank you...I already understand all of that...what does that have to do with what I said? It's only 64mA across the load, I give up, what do you think an "inductive kick" off a 64mA choke is really going to do? You don't honestly believe you are going to trip a breaker or blow a component with that small of a value across the load, not to mention we are talking about parallel and not series. Is this a joke?Alan
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