JPS6011714Y2 - Forced air cooling device for current conductors - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a forced air cooling device for a current conductor that generates heat due to the passage of current, such as a phase-separated busbar in a power plant.

Since large currents flow in the main circuit between the generator and the main transformer of a power plant, for safety reasons, the conductors of each phase should be covered with a grounded metal busbar. There are many.

In this case, the current flowing in the main circuit will raise the temperature of the conductor and cover of the phase separation bus, so in order to maintain the permissible temperature of the material, it is necessary to keep the current below a certain level. Capacity will decrease.

Therefore, in order to allow more current to flow through a bus bar of a certain size, forced cooling is generally performed using a fan driven by an electric motor.

However, conventional cooling fan drive motors use squirrel cage induction motors with a constant rotation speed that are directly turned on and started by the on-site power supply, and multiple such motors are installed to operate them. Control the number of machines or
It was under N-OFF control.

As a result, even during light loads with low bus current, an air volume close to that at full load is supplied to the bus, and cooling control that is optimal for the load condition cannot be performed, resulting in more cooling than necessary, resulting in unnecessary power consumption. has been done.

The present invention was developed in view of this point, and provides a forced air cooling device for current conductors that can supply a necessary and sufficient amount of air as the current increases, thereby preventing unnecessary power consumption. The purpose is to provide

Hereinafter, an embodiment of the present invention will be described in the case of a phase-separated bus bar with reference to the drawings.

In FIG. 1, the main circuit connecting the engine 1, main transformer 2, station transformer 3, and PT 4 in the power plant is formed by a phase-separated bus 5, and this phase-separated bus 5 is cooled with forced air by a fan 6. This fan 6 is equipped with an electric motor 7 whose number of poles can be changed.
The number of poles of the motor 7 is switched by detecting the current in the main circuit by the CT 8 and depending on the current value.

That is, the heat generated by the phase separation bus 5 is generated by the current flowing through it, and although there is a slight time delay, the heat generation roughly matches the current value, and therefore, as described above, the current is Optimum cooling can be achieved by detecting this and controlling the amount of air supplied to the phase separation bus 5.

Note that 9i is an ammeter that displays the current of the main circuit, and 10 is an in-house power supply system.

Fig. 2 shows a relay circuit that detects the current of CT3, that is, the current value of phase separation bus 5. Reference numeral 11 indicates a relay circuit that detects the current of CT3, that is, the current value of phase separation bus 5; Current relay operating at 12 is the same <60
% or more Current relays 13 are the same current relays that operate at <50% or more, and are connected in series to CTg.

Figure 3 shows a control circuit for switching the number of poles of the motor 7, where 14 is an auxiliary relay that switches the number of poles of the motor 6 and makes its rotation speed 100% of the rated speed, 15 is an auxiliary relay that sets the rotation speed to 75%, and 16 is 50%. An auxiliary relay 17 is an auxiliary relay that stops the electric motor 7.

In addition, 11A is the normally open contact 1 of the current relay 11, IIB is the normally closed contact, 12A is the normally open contact of the current relay 12, and 12B
is a normally closed contact, 13A is a normally open contact of current relay 13, 13
B is a normally closed contact.

Further, 18 is a control power source.

In the above, the current of the phase separation bus 5 is 75% of the full load current.
% or more, all current relays 11 to 13 are activated 1, closing contact 11A and opening contact 11B.

Therefore, the auxiliary relay 14 is activated to rotate the electric motor 7 at 100% of the rated speed, thereby maximizing the air volume supplied by the fan 6.

At this time, contact 11B is open and auxiliary relay 15 does not operate, contact 12B is open and auxiliary relay 16 is not operated, and contact 13B is open and auxiliary relay 17 is not operated.

Next, when the current of the phase separation bus 5 becomes 60% of the full load current, the current relays 12 and 13 operate, and the contacts 11B,
12A is closed, the auxiliary relay 15 operates, and the motor 7
Rotate at 75% of rated speed to reduce air flow supply.

When the current reaches 75% of the full load current, contact 11B is opened, auxiliary relay 15 is demagnetized, and contact 11A is closed, activating auxiliary relay 14 as described above.

In this way, only the auxiliary relay 15 operates when the current is between 60% and less than 75% of the full load current.

Similarly, when the current is less than 50% to 60% of the full load current, only the auxiliary relay 16 operates to further reduce the supply air volume, and when the current becomes less than 50% of the full load current, the contact 13B remains closed. The auxiliary relay 17 is activated to stop the rotation of the electric motor 7.

As explained above, according to the present invention, in a forced air cooling device for a current conductor that generates heat due to the passage of current, a cooling fan driven by a variable speed motor and a current detector that detects the load current of the current conductor are provided. and a plurality of current relays that are connected to this current detector and operate when the value of the load current reaches a predetermined value that is different from the total load current, and through the auxiliary contacts of these current relays. a plurality of auxiliary relays connected between the control power sources, operated by the operation of the current relay according to changes in the load current, and rotating the variable speed motor for the cooling fan at different predetermined rates relative to the rated speed; This configuration prevents unnecessary power consumption and contributes to energy conservation.

Furthermore, a sufficient amount of air can be supplied depending on the state of the load current of the current conductor, and a sufficient cooling effect can be obtained.

Furthermore, since the current relay and auxiliary relay are operated according to the magnitude of the load current to control the rotational speed of the variable speed motor, the circuit configuration is simple and the number of relays can be further increased. It is possible to perform more fine-grained control that further suppresses unnecessary power consumption.

Although the above is about a pole change motor, it goes without saying that variable speed motors based on other principles such as those using thyristors can also be used, and the objects to be cooled are limited to phase-separated buses. It can also be applied to other current conductors that generate heat when current passes through them.

[Brief explanation of drawings]

Figure 1 is a main circuit diagram of the power plant, Figure 2 is a relay circuit diagram, and Figure 3 is a motor pole number conversion circuit diagram. 1... Generator, 2... Main transformer, 3.
...In-house transformer, 4...PT, 5...
... Phase separation bus bar, 6 ... Fan, 7 ...
...Electric motor, 8...CT, 9...
Ammeter, 10... In-house power supply system, 11-13.
...Current relay, 14-17...Auxiliary relay 18...Control power supply.

Claims (1)

[Scope of utility model registration request] In a forced air cooling device for a current conductor that generates heat due to the passage of current, a cooling fan driven by a variable speed electric motor;
a current detector that detects the load current of the current conductor; and a plurality of current relays that are connected to the current detector and operate when the value of the load current reaches a predetermined value that is different from the total load current. and the control power supply through the auxiliary contacts of these current relays, and are operated by the operation of the current relays in response to changes in the load current, and the variable speed motors for the cooling fans are operated at different speeds relative to the rated speed. A forced air cooling device for a current conductor comprising a plurality of auxiliary relays that rotate at a predetermined rate.