JPS6338503Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a neutral electrode energizer and disconnector used to prevent damage to fluorescent lamps with electronic ballasts.

A fluorescent lamp with an electronic ballast rectifies alternating current, supplies this rectified voltage to a semiconductor circuit, and generates a high frequency and high voltage of 30 to 40 KHz using an oscillation circuit formed by the semiconductor circuit. It is designed to turn on a light. In recent years, this type of fluorescent lamp has come to be used in three-phase, four-wire systems, which are used as low-voltage power distribution systems in buildings, station electrical rooms, and the like.
The fluorescent lamps used in this three-phase, four-wire system are for 240V, but since these lamps generally do not have enough voltage withstand capacity, they are prone to the following problems. That is, a three-phase, four-wire electric circuit has a neutral pole and a disconnector inserted therein. The neutral pole of this loop breaker is usually closed at the same time or earlier than the voltage pole, and when opened, it is opened later than the voltage pole. However, since there is a difference between the current flowing through the voltage pole and the current flowing through the neutral pole, when the arc time is taken into account, the neutral pole may open before the voltage pole. If the neutral pole is opened before the voltage pole as described above, the fluorescent lamp may be damaged in the following cases. Figure 1 shows an example of a 3-phase 4-wire system. In the figure, 1 is the power supply side, 2 is the load side, and there are two fluorescent lights on the A phase 2a of the load side 2, and two fluorescent lights on the C phase 2c. If 10 of them are connected, b
It is assumed that phase 2b is unloaded. Reference numeral 3 is an air switch or disconnector, 3a to 3b are voltage poles, and 3d is a neutral pole.
A phase 2a and c on the load side 2 in such a state
The impedance ratio with phase 2c is 10:2, and a
The applied voltage Ea of phase 2a is expressed by the following equation.

Ea = 420 _(V) × 10/10 + 2 = 350 _(V) That is, as mentioned above, when the neutral pole is opened before the voltage pole, the series circuit of the loads of phase A 2a and phase C 2c is instantaneously connected. A voltage close to √3 times the rated voltage (phase voltage) is applied to the lamp, causing damage to the fluorescent lamp. For this reason, the neutral pole switch or disconnector may not be used, and the three pole switch or disconnector and the neutral pole switch may be configured separately. However, since the neutral pole switch may be opened inadvertently or forgotten to be turned on, it is not preferable to separate the three pole air disconnector and the neutral pole switch as described above. Therefore, in recent years, a loop breaker has been developed in which an interlock is provided between the neutral pole and the switching mechanism of the other three voltage phase poles. This loop breaker allows the neutral pole to be opened only when the voltage pole is opened by pressing a button. In this way, the neutral pole is normally in the closed state, so if this breaker is applied, for example, to the main breaker of the secondary transformer, the neutral pole current when one bank is stopped is There is a risk of deterioration in the sensitivity of the ground fault relay due to wraparound. In addition, if a branch circuit is installed on the load side and a ground fault occurs in that branch circuit, the structure is such that the neutral pole cannot be opened automatically, so the neutral pole must be opened manually. There is a risk that the neutral line potential of the system may remain connected. Furthermore, since a large current flows through the neutral electrode, there is a risk that its contacts may become welded together, and to avoid this, means are used to detect the current in the neutral electrode and quickly break the neutral electrode. This has the disadvantage that the structure is complicated.

The object of this invention is to eliminate the above-mentioned drawbacks, simplify the structure, and provide a neutral electrode energizer or disconnector that is free from the risk of reducing the sensitivity of the relay.

An embodiment of this invention will be described below with reference to the drawings. In FIG. 2, 11a, 11b, 11c
is the voltage pole of the aerial disconnector 11, and 11d is the neutral pole. A resistor 12 serving as an impedance element is connected in parallel to the neutral pole 11d. When the resistor 12 is connected to the neutral electrode 11d in this way, even if the neutral electrode 11d is opened or when it is cut off, the neutral electrode will be cut off before the electrode due to the difference in arc time. Even in this case, since the neutral pole 11d is not opened, the neutral point of the load does not move extremely. Without the resistor 12, the neutral point of the load would shift in accordance with the unbalanced load, and an overvoltage would be applied to the lightly loaded phase, causing the above-mentioned problems.

Note that the resistance value of the resistor 12 needs to be greater than a predetermined value in order to prevent the neutral pole current from sneaking around when the bank is inactive.

3 and 4 show other embodiments of this invention, in which the diode 13 connected in antiparallel is connected between the neutral pole 11d;
The figure shows a resistor 12 or a diode 13 and a contact 14 provided in series with a link of a disconnector (not shown).

In addition, in FIGS. 2 to 4 above, the resistor 1
Current flows through the resistor 12 or the diode 13 only when the circuit breaker 11 is opened, but the current is suppressed by the resistor 12 or the diode 13 itself, so the current capacity of the resistor 12 or the diode 13 is Since it can be made extremely small, it is small and inexpensive. Furthermore, in the case of FIG. 4, maintenance and inspection can be facilitated by opening the point 14.

As mentioned above, according to this invention, since an impedance element is provided between the neutral poles, it has the advantages of a normal 4-pole and disconnector, has a simple structure, and has a neutral load This has the effect that the point does not move excessively and that the sensitivity of the relay does not decrease.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a neutral-pole air breaker used in a 3-phase 4-wire system, Figure 2 is a configuration diagram showing one embodiment of this invention, and Figures 3 and 4 are It is a block diagram which shows another Example of an invention. 11...Air disconnector, 11a, 11b, 11
c...voltage pole, 11d...neutral pole, 12...resistance, 13...antiparallel connected diode, 14...contact.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A neutral pole disconnector made by connecting an impedance element between the neutral poles. (2) The neutral polarity interrupter as set forth in Claim 1 of the Utility Model Registration Claim, in which the impedance element is of low resistance. (3) The neutral polarizer or disconnector according to claim 1 of the utility model registration, wherein the impedance element is composed of diodes connected in antiparallel. (4) Utility model registration claim 1 consisting of an impedance element connected in series with a link contact for a disconnector
2. The neutral polarized air breaker and disconnector according to item 2, item 2, or item 3.