Arc suppressing circuit employing a triggerable electronic...

Details Arc suppressing circuit employing a triggerable electronic... Arc suppressing circuit employing a triggerable electronic...

2001-05-18

2003-09-23

Nguyen, Matthew V. (Department: 2836)

Electricity: electrical systems and devices

Safety and protection of systems and devices

Arc suppression at switching point

C361S003000

Reexamination Certificate

active

06624989

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to electronic switches and, more particularly, to an arc suppressing circuit employing a triggerable electronic switch to protect switch contacts.
BACKGROUND OF THE INVENTION
In systems where power to a load is switched using an electro-mechanical switch, wear of the contacts of the switch often occurs due to sparking or arcing between the contacts of the switch primarily during times of opening and closing of the switch and, more particularly, when the switch contacts “bounce” during closing of the switch. Arcing across the contacts arises due to a voltage difference across the contacts of the electrical switch that is caused by the bouncing of the switch contacts. To illustrate an example of circuit conditions occurring during bouncing of an electro-mechanical switch, FIGS.
4
and
5
A-
5
C show a conventional relay switching circuit and the voltage and current conditions occurring in the circuit. The circuit
400
shown in
FIG. 4
illustrates a relay switching circuit including a voltage source
402
supplying voltage through a relay switch
404
to a load
406
(e.g., a motor). The relay switch
404
has two contacts
408
and
410
, which are electrically connected together when a voltage from source V
2
is applied to relay coil
412
.
As illustrated in
FIG. 5A
, a voltage is present across contacts
408
and
410
when the switch
404
is open. At a time t
1
, the relay coil
412
is energized thereby creating a magnetic field that presents a force to close switch
404
. After a time delay from time t
1
to time t
2
, the contacts
408
and
410
of switch
404
are electrically connected together and the voltage across the contacts drops to zero volts as shown in FIG.
5
A. Also at time t
2
the voltage is delivered to the load
406
and current begins to flow through the load
406
as shown in FIG.
5
B. The switch
404
, however, tends to bounce, which creates arcing across the contacts of the switch
404
due to a voltage arising due the break of electrical contact. This voltage rise due to bouncing of the switch
404
is illustrated in
FIG. 5A
between time t
2
and time t
3
. It is this voltage rise and associated arcing that causes wear to the contacts of the electrical switch.
One approach to mitigate the effects of arcing in power control circuits that have need for relay switching (e.g., motor controllers) is to use solid state relays since their life exceeds that of conventional electro-mechanical relays. Electro-mechanical relays are shorter lived due to the arcing explained above. Solid state relays, however, are much more costly than conventional electro-mechanical relays and require heat sinking, which increases the space required for the solid state relay. In cases where the cost or size of solid state relays is prohibitive, substitution is usually made by providing a larger and higher rated electro-mechanical relay so as to increase the life of the relay contacts in a particular circuit. This, however, also increases the cost and size requirements for the electro-mechanical relay switching.
Another approach to mitigating contact wear, is to employ arc suppression circuits that prevent or extinguish arcing by shorting in parallel with a switch during periods of arcing, thereby increasing the switch life. Some known arc suppressing circuits include a triggerable electronic switch, such as a triac, in parallel with a switch. In such circuits, the triac is typically triggered by a triggering circuit that senses when voltage is present across the contacts or triggers during known periods of contact opening, closing or bouncing. Such triggering circuits can be complex and add components to the switching circuitry, which increases cost and complexity of the circuit. Additionally, the circuits typically require heat sinking of the triac semiconductor due to the triac conducting for a number of AC cycles, which increases the space needed for the arc suppression circuitry.


REFERENCES:
patent: 3558910 (1971-01-01), Dale
patent: 4025820 (1977-05-01), Penrod
patent: 4531172 (1985-07-01), Mertz
patent: 4709294 (1987-11-01), Kim
patent: 5283706 (1994-02-01), Lillemo et al.
patent: 5633540 (1997-05-01), Moan

Affiliated with

Also associated with

Rating

Arc suppressing circuit employing a triggerable electronic... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Arc suppressing circuit employing a triggerable electronic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Arc suppressing circuit employing a triggerable electronic... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3052373