JP5592181B2 - Low power cable - Google Patents

Description

  The present invention relates to a power control device using a continuous pulse typified by an inverter and a power cable for reducing a charging current generated with a switching operation of a drive device.

  As energy saving measures, for example, driving of lighting fixtures such as motors, fluorescent lamps, and high-pressure lamps, driving by continuous pulses typified by inverters, and the use of power control devices are increasing. The power cable is charged and discharged along with the continuous pulse switching. In particular, in an inverter that operates at a high repetition frequency, charging and discharging are performed frequently, increasing the charging current and increasing the power consumption. The charging current accompanying discharge is a problem. In conventional power cables, it is generally known how to increase the conductor size and reduce the electrical resistance in order to reduce the power consumption generated by the conductor when the current in the low frequency band required by the load is applied. It has been. However, it is not considered to reduce the power consumption generated by the charging current in the high frequency band accompanying charging / discharging of the power cable.

International Publication No. 2008-041708

As shown in FIG. 2, the power cable used in a system that controls electric power by continuous pulses, such as the motor drive by the inverter of FIG. 1, is repeatedly charged and discharged as the pulses are switched. Charging occurs when the pulse switches from off to on, and discharge occurs when switching from on to off. During this charging, a charging current corresponding to the type and length of the power cable flows into the power cable. For example, a cabtyre cable, which is a conventional power cable, generates the power consumption shown in Table 3 regardless of the current in the low frequency band required for the original load. Furthermore, this charging current flows as a leakage current between phases and between grounds, and contributes to conduction noise and radiation noise. Here, the power consumption associated with charging / discharging of the power cable is the power consumption when a power meter is installed on the inverter input side as shown in Fig. 3 and when the power cable is connected to the inverter. Measure and take the difference. The non-inverter connection end of the power cable is open.

For example, in a motor drive system using an inverter, a pulse input to a power cable by the inverter propagates to the motor end while charging between the phases and the ground of the power cable and is reflected at the motor end. The charging current flows into the power cable until the pulse reflected at the motor end reaches the inverter end. The power consumption P generated by this charging current is given by Equation 1 by the pulse voltage Ec, the charging current i flowing into the power cable, and the pulse repetition frequency f.


P = ∫Ec ・ i
dt x f (Formula 1)

Thereby, in order to suppress power consumption P, it turns out that power consumption can be reduced by reducing charging current. The charging amount Ic of the charging current flowing into the power cable can be approximated by the product of the charging current value Im and the charging time tc as shown in FIG. The charging current value is determined by the characteristic impedance between the pulse voltage and the phase of the power cable and between the ground, and the charging time is reflected at the motor end after propagating through the power cable after the charging current is input to the power cable. This is the time it takes for the reflected charging current to reach the inverter end, and is proportional to the power cable length. Based on this knowledge, the present invention provides a power cable having a lower charge amount than that of a conventional power cable as a reduction in power consumption and noise countermeasures associated with charging / discharging of the power cable. The purpose is to provide.

In order to solve the above problems, the power cable of the present invention reduces the amount of charge as the product of the charging current value and the charging time and further reduces the leakage current as compared with the conventional power cable. It is necessary to provide an insulation structure with a low effective dielectric constant between the phase and the ground so that the characteristic impedance is 10Ω or more higher than that of the conventional power cable, and further the charging time per unit length is 10 ns or less. Features. Here, in the present invention, the low effective dielectric constant means an effective dielectric constant of 2 or less. In addition, when measured, the insulation core wire and the sheath of the cabtyre cable, which is a conventional power cable, have an effective dielectric constant in the range of about 2.3 to 3.4.

Further, the power cable of the present invention reduces the charging current value and further reduces the leakage current as compared with the conventional power cable, and has a characteristic impedance higher than that of the conventional power cable by 10Ω or more. In addition, the magnetic material is arranged on the insulating coating or sheath of each insulating core wire, or arranged so that the outer periphery or insulating core wire of each insulating core wire is bundled. An example of characteristic impedance of a typical conventional power cable is shown in Table 4, and the measurement method is shown in FIG.

Charge amount and power consumption of a power cable 50 m of 4 cores and a conventional power cable VCT4-2 mm2 50 m using a foamed polyethylene of insulation polyethylene of the present invention shown in the first embodiment of FIG. The comparison results are shown in Table 6, and the charging current waveform is shown in FIG.
According to the present invention, by reducing the charging amount of the power cable, an effect of suppressing power consumption generated in the power cable to be used can be obtained regardless of the power required for the original load, and energy saving can be realized. Further, in the present invention, it is possible to provide a power cable having a large industrial value that can save energy at low cost without changing a control device such as an inverter.

Inverter motor drive system example Pulse voltage and current flow into the power cable Measurement of power consumption associated with power cable charging / discharging Enlarge current waveform when charging power cable 4-core cabtyre cable characteristic impedance measurement Charging current waveform First embodiment Second embodiment Third Embodiment (a) Cable structure (b) Cordel insulator structure Fourth embodiment Fifth embodiment

A first embodiment is shown in FIG. This is an embodiment corresponding to the invention according to claim 1 or claim 3, and foamed polyethylene having a foaming degree of 30% is used for the insulation coating and sheath of each insulation core wire.
A power cable in which a plurality of insulation core wires 1 each having a low effective dielectric constant insulation coating 1b made of a highly foamed insulator are twisted around the conductor 1a and a sheath 9 having a low effective dielectric constant is provided thereon. A low effective dielectric constant of 1.95 is achieved between conductors 1a, 2a, 3a, and 4a by applying a low effective dielectric insulating coating such as high foam insulation on the outer periphery of the conductor, realizing a reduction in charge.

A second embodiment is shown in FIG. This is an embodiment corresponding to the invention as set forth in claim 4, wherein a hollow structure is provided as a gap between each insulated core wire and between each insulated core wire and the ground.
A power cable in which a plurality of insulating cores 1 each having an insulation coating on the outer periphery of a conductor 1a are twisted together with an insulator 5 such as a hollow structure and a sheath 9 is provided thereon. A low effective dielectric constant of 1.85 is provided between conductors 1a, 2a, 3a and 4a by providing a low effective dielectric insulator between each core wire and further ensuring a separation distance between the conductors by a hollow insulator. Achieves a reduction in charge.

A third embodiment is shown in FIG. This is an embodiment corresponding to the second aspect of the invention, and an insulator having a low effective dielectric constant of 2 or less is used for each insulating core wire.
A power cable in which a plurality of core wires 1 each having a cordel 1c wound around an insulating core wire having an insulating coating 1b on the outer periphery of the conductor 1a are twisted and a sheath 9 having a low effective dielectric constant is provided thereon. By using a Cordel-type insulator, a low effective dielectric constant is provided between the cores, and by securing a separation distance between the conductors, a low effective dielectric constant of 1.24 is provided between the conductors 1a, 2a, 3a, and 4a. Realize a reduction in quantity.

A fourth embodiment is shown in FIG. This is an embodiment corresponding to the invention described in claim 6 or claim 7, and a symmetrical structure is used in which an insulating material is applied to the insulating core wires and the return line has a low inductance.
Three insulation cores 1 with an insulation coating 1b on the outer circumference of the conductor 1a, as viewed from the cable cross-sectional direction, each insulation core is arranged independently on three vertices of an equilateral triangle, Each of the three return lines 6 is arranged independently at three vertices of an equilateral triangle, and is twisted so that the vertex of the insulation core and the vertex of the return line have a misalignment angle of about 45 degrees. A power cable having a ferrite tape 8 on its outer periphery and a sheath 9 thereon. Conductive noise is reduced by using a symmetric structure, and radiation noise is reduced by the outer peripheral ferrite tape. Further, by separating the return line and the insulation core line by the interposition 7, the conductors 1a, 2a, 3a and the return line 6 are made to have a low effective dielectric constant of 1.94, and the amount of charge is reduced.

A fifth embodiment is shown in FIG. This is an embodiment corresponding to the invention described in claim 1 or claim 4, in which a hollow structure is provided as a gap between each insulated core wire and between each insulated core wire and ground.
Insulating coating 10 is applied to conductors 1a, 2a, 3a, and 4a, and when viewed from the cross-sectional direction of the cable, each conductor is arranged on approximately four vertices of a square, and a sheath 9 having a low effective dielectric constant is applied thereon. Power cable. Adjacent conductors are arranged on the same circumference at positions rotated by approximately 90 degrees to ensure a separation distance, and further, strength is ensured by the hollow insulator 5 and 1. 1 between the conductors 1a, 2a, 3a and 4a. A low effective dielectric constant of 74 is realized to reduce the amount of charge.

1a conductor 1b insulator 1c
Cordel 2a Conductor 3a Conductor 4a Conductor 1 Insulating core wire 5 Insulator 6 Return wire 7 Interposition 8 Ferrite tape 9 Sheath 10 Insulator

Claims (4)

It is a power cable that suppresses the charge / discharge current that occurs with continuous pulses, so as to increase the characteristic impedance between phases and ground so as to reduce the amount of charge as the product of the charge current value and the charge time, Further, an insulator made of foamed polyethylene having a low effective dielectric constant of 2 or less on the insulation coating and sheath of each insulating core wire so that the effective dielectric constant of the insulator between the conductors becomes a low effective dielectric constant of 2 or lower. A power cable characterized by having a configuration using a cable. The insulation core wire is obtained by twisting a plurality of insulation core wires having a low effective dielectric constant insulation coating made of the foamed insulator on the outer periphery of a conductor, and a sheath having a low effective dielectric constant is provided thereon. The power cable according to claim 1. The power cable according to claim 2, wherein foamed polyethylene having a foaming degree of 30% is used as an insulator for the insulation coating and the sheath of each of the insulation core wires. A power cable that suppresses the charging / discharging current generated by continuous pulses, and is characterized by a symmetrical structure so that the return line has a low inductance so as to reduce radiation noise or conduction noise caused by the charging current. claim 1 Symbol placement power cable of the.