Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Patent
1997-05-07
1999-09-14
Reichard, Dean A.
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
174 84R, 174 89, 174113C, 439 98, 439610, H02G 1502
Patent
active
059526130
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a connector according to the preamble of claim 1 for connecting a three-phase cable.
The invention also concerns a manufacturing method for the connector.
Connection of a three-phase squirrel-cage or synchronous motor in inverter-driven systems is most frequently performed by means of a copper or aluminium cable having three symmetrically placed phase conductors surrounded by a common concentric earth conductor. Connection to the drive acting as the load is conventionally performed using a terminal block at low current levels and cable lugs at higher current levels. The concentric earth conductor is bundled into a "tail" diverted from the side of the cable and then connected using either of the above-mentioned termination methods.
Such a termination method has several shortcomings. Firstly, the joint unavoidably becomes long end bulky, because the phase conductors must be diverted apart from each other prior to the jointing. Secondly, at least four separate jointing steps must be carried out, three for the phase conductors and one for the earth conductor. In the case of segmental phase conductors, they must be dressed into a round shape before jointing. Besides the connections, the cable must be secured by means of a separate strain relief.
The phase and earth conductors, which are diverted apart from each other for the connection, form loops and radiating dipoles for the currents passing through them thus giving rise to stray inductances and emission of electromagnetic fields to their surroundings. To avoid such interference, the phase conductors should be arranged to run as symmetrically and as close to each other as possible. Furthermore, the length of the phase conductors exposed from under the concentric earth conductor should be minimized.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome the drawbacks of the above-described technology and to provide an entirely novel connector for connecting a three-phase cable and a method for manufacturing such a connector.
The goal of the invention is achieved by means of providing a purpose-designed symmetrical connector for connecting a cable in inverter-driven systems, in which connector the insertion of all three phase conductors into the connector occurs in a single jointing step and the earth connector is continued in its concentric form into the interior of the connector housing. Simultaneously, the concentric jointing of the earth conductor acts as the strain relief for the cable.
More specifically, the connector according to the invention is principally characterized by what is stated in the characterizing part of claim 1.
Furthermore, the method according to the invention is principally characterized by what is stated in the characterizing part of claim 3.
The invention offers significant benefits.
Jointing can be made in a single step. At the same time the jointing step provides an effective strain relief. Moreover, the embodiment according to the invention provides an electrical interference level much lower than that of conventional constructions. Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention will be examined in greater detail with reference to exemplifying embodiments illustrated in the appended drawings in which:
FIG. 1 is a side view of a connector according to the invention;
FIG. 2 is a cross-sectional view along the plane 2--2 of the connector shown in FIG. 1;
FIG. 3 is a cross-sectional view along the plane 3--3 of the connector shown in FIG. 1;
FIG. 4 is a cross-sec
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patent: 4243290 (1981-01-01), Williams
patent: 4420202 (1983-12-01), Atakkam
ABB Industry OY
Mayo III William H.
Reichard Dean A.
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