JPH04217795A - Starting protection device for fan motor in cross flow type cooling tower - Google Patents

Abstract

PURPOSE:To make it possible to start properly a fan motor without tripping when starting a first fan which carries out additional operation in simple structure and protect said motor from excess load definitely and hence maintain safety. CONSTITUTION:A portioning wall 30 which cuts off the suction side of a second fan 8 which caries out additional operation against the suction side of a first fan 7 during operation, is installed to a chamber 20 on a filler secondary side so that reverse load may not be imposed when the second fan 8 starts. The preset value of an over current relay 22 to be connected with a fan motor 17 for the second fan 7 is rated identical to that of an over current relay 21 connected with a motor 16 of the first fan 7 which starts in a rated manner.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a fan motor activation protection mechanism in a cross-flow type cooling tower, and more particularly, to a cross-flow type cooling tower equipped with a plurality of fans, in which the fans are sequentially activated in a timed manner,
The present invention relates to a start-up protection mechanism for protecting the start-up of a fan to be additionally operated with respect to the currently operating fan when the number of units is controlled according to the load.

0002

BACKGROUND OF THE INVENTION Conventionally, a cross-flow type cooling tower is disclosed in, for example, Japanese Utility Model Application Publication No. 1-101096, and as shown in FIG. An upper hot water tank C is provided above the filler B, and a lower cold water tank D is provided below the filler B, and a fan E is provided within the spacing between the fillers B so as to prevent the hot water from flowing down the filler B in the direction of flow. Air is circulated in orthogonal directions, and a large-sized cooling tower is known in which a plurality of the fans E are provided in the direction in which the filler B is arranged, as shown in FIG. .

[0003] In the case where a plurality of the fans E are provided, each of the fans E is sequentially activated for a limited time, or the number of operating fans is controlled according to the load to control the capacity. In FIG. 5, OC is a thermal overcurrent relay connected to the power supply circuit of the fan motors M1 and M2 of each fan E.

0004

[Problem to be Solved by the Invention] However, in the case where a plurality of fans E are used as described above, and the capacity is controlled by sequentially starting these fans E in a timed manner or by controlling the number of operating fans according to the load, for example, as shown in FIG. While one fan motor M1 is operating in the conventional example shown in FIG.
When the fan E is stopped, the fan E driven by the fan motor M2 is induced by the suction flow of the operating fan E and rotates in the opposite direction, as shown by the arrow in FIG.

[0005] When the fan motor M2 is started for a limited time from the reverse rotation state or is additionally started due to an increase in load, the reverse load acts on the fan motor M2 and the overcurrent relay OC is activated. There was a problem in that the motor M2 was activated and the motor M2 tripped.

By the way, the fan E used in the cooling tower is normally a propeller fan, but this fan has a large moment of inertia and takes a long time to complete starting, for example, in the case of a 4 to 6 pole motor, it takes about 5 seconds. It has a certain length.

[0007] When a propeller fan with such a large moment of inertia is started while rotating in reverse, the reverse load is large and therefore the time required to complete the start is longer.

For example, as shown in FIG. 6, when using a 6-pole motor at the rated rotation speed of 1200 rpm,
Assuming a 30% reverse load, approximately 360 rpm
The start-up completion time is 6.5 seconds, which is a 30% increase compared to the rated start-up time of 5 seconds.

Therefore, if the set value of the overcurrent relay OC of the fan motor M2 to be additionally started is set in accordance with the rated start, the set value will be exceeded when the fan motor M2 is started, and the overcurrent relay will be activated. The OC activates and the car becomes inoperable.

[0010]In order to avoid this problem, the setting value of the overcurrent relay OC in the fan motor M2 to be additionally started is normally made larger than the setting value for rated starting, assuming an overload. However, this set value must be selected as a function of the starting current (settling current) and the operating time, and the above-mentioned reverse load also depends on the installation location of the cooling tower and the outside air conditions during operation, e.g. Since it fluctuates due to changes in conditions such as strong winds, incorrect selection of the setting value may cause a trip.Also, even if the selection is correct, the setting value may not be set with safety in mind. Therefore, there is a lack of safety against overload protection during steady operation.

[0011] An object of the present invention is to use a simple configuration in a cross-flow type cooling tower having a plurality of fans, and to correctly start up an additional fan without causing the fan motor to trip when starting up an additional fan. An object of the present invention is to provide a start-up protection mechanism for a fan motor that can provide reliable overload protection during steady operation and ensure safety.

0012

[Means for Solving the Problems] The present invention provides fillers 2 and 3 on at least one side of a rectangular tower body 1, upper hot water tanks 4 and 5 above the fillers 2 and 3, and upper hot water tanks 4 and 5 below. A lower cold water tank 6 is provided, and a plurality of fans 7 and 8 are provided along the direction in which the fillers 2 and 3 are disposed to blow air in a direction perpendicular to the direction of hot water flowing down the fillers 2 and 3. While circulating, the plurality of fans 7 and 8 are sequentially activated in a timed manner, or
A fan motor in a rectangular cooling tower that enables capacity control according to the load by controlling the number of operating units, and in which overcurrent relays 21 and 22 are connected to each fan motor 16 and 17 corresponding to each of the fans 7 and 8, respectively. This startup protection mechanism protects the suction side of the first fan 7 in the filling material secondary side chamber 20 when the plurality of fans 7 and 8 are timed activated or when the capacity is controlled according to the load. Partition wall 3 that blocks the suction side of the second fan 8 that is additionally operated
0, and the setting value of the overcurrent relay 22 in the fan motor 17 of the second fan 8 to be additionally operated is set to the same rating as the overcurrent relay 21 in the fan motor 16 of the first fan 7. It is characterized by:

In the present invention, the fans 7 and 8 have two
Of course, it can be applied in the same way even when three or more units are provided.Also, in the case of sequential time-limited activation, the activation order may be fixed, but may be changed.

Further, when controlling the number of fans for capacity control, the fans to be turned on and off may be fixed, but they may also be changed arbitrarily.

[0015] Therefore, each fan 7 used when changing the starting order or changing the fan to be controlled to start/stop.
The setting values of the overcurrent relays 21 and 22 in No. 8 are made to have the same rating.

The present invention can be applied not only to the case where the sequential timed activation of the fans 7 and 8 and the capacity control by controlling the number of fans in operation are used together, but also to the case where only the sequential timed activation or only the capacity control is used.

[0017]

[Operation] When starting a plurality of fans 7 and 8 in sequence for a limited time, or when controlling the capacity by controlling the number of fans in operation according to the load, additional operation is required on the suction side of the first fan 7 that is in operation. Since the suction side of the second fan 8 is blocked by the partition wall 30, the second fan 8 will not rotate in the opposite direction due to the suction flow of the first fan 7 being operated. When the second fan 8 is activated for a limited time or additionally activated due to an increase in load, a reverse load due to reverse rotation does not act on the activation of the second fan 8.

As a result, it is no longer necessary to select the setting value of the overcurrent relay 22 connected to the fan motor 17 of the second fan 8 assuming a reverse load at the time of startup. This makes it possible to eliminate tripping of the second fan 8 due to inappropriate selection of set values.

Moreover, the set value of the overcurrent relay 22 connected to the fan motor 17 of the second fan 8 which is additionally operated is the same as the overcurrent relay 21 connected to the fan motor 16 of the first fan 7 which is started at the rated value. Since they have the same rating, overload protection during steady operation can be ensured and safety can be improved.Moreover, when the second fan 8 is additionally started, the overcurrent relay 22 is activated and the second fan 8 is activated. The fan motor 17 of the fan 8 will not trip.

Therefore, with a simple configuration, it is possible to protect the fan motor 17 of the second fan 8 from starting while ensuring safety during steady operation.

[0021]

[Example] The cooling tower of the example shown in the drawings is
Fillers 2 and 3 are disposed facing each other on both sides of the square tower body 1, and above each of these fillers 2 and 3, a hot water pipe extending from the outlet side of the heat source side heat exchanger in the refrigerator is connected. The upper hot water tanks 4 and 5 are provided below, and a common lower cold water tank 6 is provided below to connect the cold water pipe extending from the inlet side of the heat source side heat exchanger, and the arrangement direction of the fillers 2 and 3 is Two fans 7, 8 are provided along the filling material 2, 3.
The air is made to flow in a direction perpendicular to the direction of hot water flowing down.

The tower body 1 has rigid louvers 23 and 24 erected on both sides of the rectangular housing forming the lower cold water tank 6 in the width direction to form a side frame. a holding frame 9 that holds the materials 2 and 3;
10 is disposed and supported by the louvers 23, 24, and outer plates 11, 12 are provided on both sides in the longitudinal direction to form a side frame together with the louvers 23, 24. fixed, and the holding frames 9, 10
The upper hot water tanks 4 and 5 are disposed on the upper part of the louver and fixed to the louvers 23 and 24, and the top plate 13 is further fixed to the upper part of the upper hot water tanks 4 and 5 and the outer panels 11 and 12. are doing.

Further, fan housings 14 and 15 are provided on the top plate 13, and the fan casings 14 and 15
supports the fans 7 and 8, and also supports the fan motor 1.
6 and 17 are provided, and are interlocked with the fans 7 and 8 for deceleration via power transmission bands 18 and 19 such as belts.

Further, in the tower body 1, a filler secondary side chamber 20 is formed by the fillers 2, 3, the outer panels 11, 12, the top plate 13, and the housing forming the lower cold water tank 6. be.

Further, the fans 7 and 8 can be activated in sequence for a limited time, and the number of fans can be controlled in accordance with the load required on the heat source side heat exchanger, so that capacity can be controlled.

That is, although not shown in the figure, a controller for controlling the operation of the fan motors 16 and 17 is used to sequentially control the timed activation, and a water temperature thermostat is used to control the operation of the fan motors 16 and 17.
The number of operating fan motors 16 and 17 is controlled by the controller via a cooling water temperature regulator.

Further, thermal overcurrent relays 21 and 22 are connected to the power supply circuits of each of the fan motors 16 and 17, respectively, to protect each of the fan motors 16 and 17 from overload. There is.

[0028] In the cooling tower constructed as described above, the filling materials 2 and 3 are driven by the fans 7 and 8.
Air is circulated as shown by the arrow in Figure 3, and the upper hot water tank 4
. After a certain period of time when the first fan 7 finishes starting, the second fan 8 is started. Also, when the operating load of each of the fans 7 and 8 decreases, the second fan 8 is started. The capacity is controlled by stopping the fan 7 and operating only the first fan 7.

In the cooling tower constructed as described above, the present invention prevents a reverse load from acting on the second fan 8, which is additionally operated with respect to the first fan 7, when it is started, unlike in the conventional example. The setting value of the overcurrent relay 22 connected to the fan motor 17 of the second fan 8 is set to the same rating as the setting value of the overcurrent relay 21 of the fan motor 16 of the first fan 7, which is set corresponding to the rated startup. That's what I did.

That is, the suction side of the first fan 7 to be operated is placed in the filler secondary side chamber 20 in the cooling tower when the fans 7 and 8 are started in sequence for a timed period and when the capacity is controlled according to the load. , a partition wall 30 is provided to block the suction side of the second fan 8 which is additionally operated, and
The setting value of the overcurrent relay 22 in the fan motor 7 of the second fan 8 which is additionally operated is made to have the same rating as the overcurrent relay 21 in the fan motor 16 of the first fan 7.

As shown in FIG. 3, the partition wall 30 has its upper edge in contact with the top plate 13 and its lower edge reaches the water surface of the lower cold water tank 6, and is divided by the partition wall 30. The hot water flowing down to the fillers 2 and 3 facing the filler secondary side chamber 20 is received by one of the lower cold water tanks 6, and is discharged from an outlet pipe (6a) provided at the drop-in part of the lower cold water tank 6. However, the suction side of the second fan 8 is blocked from the suction side of the first fan 7.

[0032] The partition wall 30 also includes the filler 2,
3 may be divided in the length direction and fixed to the louvers 23 and 24 by intervening in this divided portion, but by interposing them between the holding frames 9 and 10 of the filling materials 2 and 3, these holding frames Frame 9
, 10. In the above configuration, when the second fan 8 is activated in a timed manner, the first fan 7
The second fan 8 is stopped until the startup is completed, and is also stopped when the capacity is controlled in response to a partial load. During this stop, the suction side of the second fan 8 is not operated by the partition wall 30. Since it is cut off from the suction side of the first fan 7, which is connected to the suction side of the first fan 7, it will not be attracted to the suction side of the first fan 7 and rotate in the opposite direction.

Therefore, when the second fan 8 is additionally started from a stopped state, no reverse load is applied, and therefore, when the first fan 8 is started while both the fans 7 and 8 are stopped. The start-up is completed within the rated start-up time for starting up the second fan 7, and the overcurrent relay 22 is not activated and the fan motor 17 of the second fan 8 is not tripped during this start-up.

As a result, it is not necessary to select the setting values of the overcurrent relays 21 and 22 connected to the fan motors 16 and 17 of each of the fans 7 and 8 assuming a reverse load, so that trips due to selection errors are avoided. Since the set value can be changed to the set value corresponding to the rated start-up, standard overcurrent relays can be used in both cases, ensuring protection against overload during steady operation, and improving safety. can also be improved.

Although the embodiment described above uses two fans 7 and 8, it can be similarly applied to a case where three or more fans are used.

[0036] Furthermore, while the cooling tower in which the fans 7 and 8 are activated sequentially in a timed manner and the capacity is controlled by controlling the number of fans, the cooling tower in which the fans 7 and 8 are activated sequentially in a timed manner without capacity control or in which only capacity control is performed is also applicable. The same applies.

[0037]

Effects of the Invention The present invention is constructed as described above, and when the fans 7 and 8 are sequentially activated for a limited time, or when the capacity is controlled by controlling the number of fans in operation according to the load, additional operation is not required. Since the suction side of the second fan 8 that is stopped is blocked from the suction side of the first fan 7 that is in operation, the second fan 8 is not connected to the suction flow of the first fan 7 that is in operation. It is not induced to rotate backwards.

Therefore, when starting the second fan 8 for a limited time or additionally starting it due to an increase in load, the second fan 8
There is no reverse load due to reverse rotation acting on the start of the motor. As a result, the fan motor 17 of the second fan 8
It is no longer necessary to select the setting value of the overcurrent relay 22 connected to the overcurrent relay 22 assuming a reverse load at startup, and it is possible to prevent the second fan 8 from tripping due to a selection error.

Furthermore, since the setting value of the overcurrent relay 22 connected to the fan motor 17 of the second fan 8 is the same as the overcurrent relay 21 of the first fan 7 that starts at the rated value, Overload protection can be ensured and safety can be improved, and at the same time,
When additionally starting the second fan 8, the overload relay 22
It is also possible to prevent the second fan 8 from tripping due to the operation of the second fan 8.

[Brief explanation of the drawing]

[Fig. 1] A schematic sectional view showing an example of a cooling tower to which the mechanism of the present invention is applied.

[Figure 2] Plan view of the cooling tower shown in Figure 1

[Figure 3
] Cross-sectional view taken along line X-X in Figure 2

[Fig. 4] A sectional view corresponding to Fig. 2 showing a conventional example

[Fig. 5] A sectional view corresponding to Fig. 1 showing a conventional example

[Figure 6] Graph showing the startup characteristics when starting the fan motor

[Explanation of symbols]

1 Tower body 2,3 Filling material 4, 5 Upper hot water tank 6 Lower cold water tank 7 1st fan 8 Second fan 16, 17 Fan motor 20 Filler secondary side chamber 21, 22 Overcurrent relay 30 Partition wall

Claims (1)

[Claims] Claim 1: Fillers 2 and 3 are provided on at least one side of a square tower body 1, upper hot water tanks 4 and 5 are provided above the fillers 2 and 3, and a lower cold water tank 6 is provided below. , a plurality of fans 7 and 8 are provided along the arrangement direction of the fillers 2 and 3, and air is circulated in a direction perpendicular to the direction of hot water flowing down the fillers 2 and 3, while It is possible to control the capacity according to the load by sequentially starting the fans 7 and 8 in a timed manner or by controlling the number of units in operation, and each of the fans 7,
This is a starting protection mechanism for fan motors in a square cooling tower in which overcurrent relays 21 and 22 are connected to fan motors 16 and 17 corresponding to fan motors 8 and 8, respectively. 8 or when controlling the capacity according to the load, a partition wall 30 is provided to block the suction side of the first fan 7 to be operated from the suction side of the second fan 8 to be additionally operated. A cross flow characterized in that the set value of the overcurrent relay 22 in the fan motor 17 of the second fan 8 being operated is set to the same rating as the overcurrent relay 21 in the fan motor 16 of the first fan 7. Start-up protection mechanism for fan motor in type cooling tower.