JPH02188143A - Internal cooler for enclosed outer fan type motor - Google Patents

Abstract

PURPOSE:To prevent overheat in a motor after stoppage of motor by cooling the frame through a fan arranged at the outside of the frame of an enclosed motor while simultaneously driving an internal fan through a motor arranged in the frame. CONSTITUTION:An external fan 5 is driven through a motor 4 arranged at the inside of a fan cover 3 fixed to the frame 2 constituting the shell of a motor body 1 to feed the air as shown by arrows 13 so as to cool the fins 6 of the frame 2. An internal fan 20 born rotatably by a rotary shaft 7 is also arranged at the inside of the frame 2. A rotor 21 comprising a permanent magnet is fixed to the frame 2 side of the fan 20 while a stator 22 facing the rotor 21 is fixed to the inside of the frame 2 thus constituting an internal fan motor 23. The stator 22 is executed, immediately after stoppage or during low speed rotation of the motor 1, to drive the internal fan 20 so as to circulate the air as shown by arrows 14. By such arrangement, the motor is protected from overheat immediately after stoppage of motor or during low speed rotation of motor.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention mainly relates to an internal cooling device for a large-capacity totally enclosed external fan type electric motor. [Prior art] JISC4004 (198G) for cooling electric motors
General rules for rotating electric machines, forming ponds for refrigerant feeding (Tables 7 to 10)
), and an example of a conventional cooling device for a completely enclosed external fan type motor will be described with reference to FIG. An external fan 5 is installed inside and driven by the electric motor 4, and the fan 5 blows air to the outer surface of the frame 2 to cool the frame 2 and its heat dissipation fins 6.
An internal fan 8 is fixed concentrically to the inner cylinder, and as the rotating shaft 7 rotates, air is blown from the internal fan 8 between the frame 2 and the stator 9, and from between the rotor lO and the rotating shaft 7. The air is sucked in and contacts the inner wall of the frame 2 during circulation to cool the internal air, thereby cooling the stator winding 11. rotor conductor 12,
The entire core is cooled and kept below the allowable temperature. In addition, in the figure, 13 indicates the air flow by the external fan 5, and 14
is the air flow caused by the internal fan 8, and ■5゜16 is a wedge placed on the outer periphery of the stator 9 and the inner periphery of the rotor 10 to ensure a ventilation path. 7 is a bearing, and 18 is a bolt hole for fixing the frame 2.

[Problems to be Solved by the Invention] When the main body electric motor 1 temporarily stops, the operation of the electric motor 4 for the external fan 5 is continued, and the external fan 5 blows air to the surfaces of the frame 2 and fins 6 to clean the outer surface of the main body electric motor 1. Although it is cooling, the rotating shaft 7 is stopped, so the internal fan 8
The air flow 14 due to the stator 9 and the rotor 1 is stopped.
Therefore, the cooling efficiency of the stator winding 11 and the rotor conductor 12 also decreases. Figures 10 (a) and (b) are graphical representations of typical temperature patterns when power loss occurs inside the motor due to the starting current and is affected by temperature rise. is the starting period, N is the period of operation at constant load,
R represents the period during which the motor is stopped and no voltage is applied, and θ-aX represents the maximum temperature during operation. In the case of a relatively small-capacity electric motor with a capacity of less than a few kilometres, the frame 2, stator 9 and rotor l
Since the amount of air intervening between O and O is small, the inside is also cooled by the heat exchange action on the surface of frame 2, and as shown in Fig. 1 O (
As shown in b), the internal temperature drops from the moment the motor stops, but medium-sized and large-sized motors of several tens of kilowatts or more have a large amount of air inside, so heat conduction causes the stator windings 11 and The rotor conductor 12 enters a heat-retaining state, and as shown in Figure 1O (0), the internal temperature hardly decreases and may exceed the maximum temperature (θ-aX) at the next start, and as this process is repeated, the rotation This results in melting loss of the child conductor 12. In recent years, the stator winding 11 has become able to withstand high temperatures due to improvements in insulating materials. However, the rotor conductor 12 generally has an aluminum die-cast or copper alloy brazed structure, so mechanical In order to maintain strength, the maximum allowable temperature is 220°C to 240°C. In addition, electric motors that carry a large inertial load, high torque, and high slip electric motors are severely restricted in their starting opening, so it is currently necessary to wait several hours before the next start. In addition, variable frequency motors, which are becoming increasingly popular these days, operate at variable speeds from 10:1 to 200:1, but when the speed drops below the rated speed of 174, the effectiveness of the internal fan decreases, so countermeasures have been taken. The rated output is set to 1 to 2 frames (1,
A motor that is about 4 to 2 times thicker is selected. Therefore, as a means to maintain internal cooling even when the internal fan 8 stops or rotates at low speed, the motor body l is equipped with a heat exchanger to ensure sufficient cooling during operation so that there is no problem even if the internal fan 8 stops. A method in which the device is kept in place is also currently used, but it has the disadvantage that the entire device is expensive. In view of the above-mentioned circumstances, the present invention allows the external fan and internal fan to continue operating even when the main motor stops, thereby cooling the stator and rotor, as well as the stator windings and rotor conductors. An object of the present invention is to provide an internal cooling device for a full-gate external fan-shaped electric motor. In the all-gate external fan type electric motor provided with an external fan for blowing air, an electric motor for the internal fan is provided inside the frame, and an internal fan is provided for blowing air inside the main body motor using the electric motor for the internal fan as a power source. The fully open external fan type motor is characterized in that an external fan for blowing air to the external surface of the frame is provided on the outside of a frame forming the outer shell of the main motor, and a power transmission device connected to the motor shaft of the external fan to the frame. The device is characterized in that an internal fan is provided which is disposed through the device and blows air into the main body motor using the external fan motor as a power source via the power transmission device. [Function] Even if the main motor stops temporarily or continues to operate at low speed, the internal fan continues to operate together with the external fan, so the inside of the main motor can be air-cooled. [Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings 1 to 8. In addition, Fig. 1, Fig. 4, Fig. 5, Fig. 6,
In FIGS. 7 and 8, the same components as those shown in FIG. 9 are given the same reference numerals. FIG. 1 shows an embodiment of the present invention, in which an internal fan 20 is rotatably attached to a cylindrical portion of a frame 2 of a rotating shaft 7 concentrically with the rotating shaft 7 via a bearing 19.
On the back side, the surface opposite to the internal fan 20 side is the rotating shaft 7.
A donut-shaped flat rotor 2I that is flat perpendicular to the direction and concentric with the rotating shaft 7 is fixed, and a flat rotor 2I that faces the rotor 21 concentrically and whose surface is flat is fixed inside the frame 2. An internal fan 20Jlf1m that can rotate a flat rotor 21 and an internal fan 20 by fixing a flat stator 22 and passing an alternating current through the windings of the hand-shaped stator 22.
Form motive 23. The flat rotor 21 has a structure in which conductors are embedded radially near the surface of a donut-shaped core and these conductors are connected to short-circuit rings arranged on the outer and inner peripheries, but the structure is not limited to this type. An aluminum disk may be attached to the surface of the iron core, or only an aluminum disk may be used. Figures 2 and 3 are diagrams showing the principle of generating a rotating magnetic field in the two-pole, three-phase flat stator 22. When the instantaneous maximum current flows through a phase, a magnetic field is generated in the direction of the arrow in Figure 2 (a). As shown in Figure 3 (b), after 30° has elapsed in phase, when the currents in the R and S phases become 87% in instantaneous value and the current in the T phase becomes zero, the magnetic field changes to the third phase.
As shown in the figure, the rotating magnetic field is also obtained in the flat stator 22, so the flat rotor 21 is placed so as to face it.
can generate rotational torque. Note that it is also possible to adopt a grooved stator winding structure such as full-pitch overlapping winding as in a general-purpose motor. Therefore, when the main motor l stops, the flat stator 2
By passing current through the second winding, the internal fan 20 rotates, causing both the external fan 5 and the internal fan 20 to rotate, and the internal wall of the frame 2 and internal air exchange heat, resulting in ), the internal temperature decreases before the next start, so the rotor conductor 12 does not need to be equipped with an expensive heat exchanger.
It is possible to prevent melting loss. FIG. 4 shows another embodiment of the present invention, in which an internal fan 20 is rotatably mounted concentrically with the rotary shaft 7 via a bearing 19 as in FIG. 1, and rotates on the back side of the internal fan 20. axis 7
A donut-shaped cylindrical rotor 21a concentric with is fixed,
Further, a cylindrical stator 22a having a cylindrical shape is fixed inside the frame 2 so as to face the surface of the rotor 21a concentrically, and by passing an alternating current through the cylindrical stator winding, the cylindrical stator 22a is fixed. An electric motor 23 for the internal fan 20 that can rotate the rotor 21a and the internal fan 20 is formed. The cylindrical rotor 21a has a structure in which conductors are embedded near the surface on the side facing the cylindrical stator 22a, and these conductors are connected to short-circuit rings arranged at both ends, but the shape is not necessarily limited to this. Alternatively, an aluminum cylinder may be attached to the surface of the iron core, or only an aluminum cylinder may be used. Although not shown in the drawings, the cylindrical stator 22a and the cylindrical rotor 21a can also form the electric motor 23 in the relationship of an inner cylinder and an outer cylinder, respectively. That is, the stator winding of the cylindrical stator 22a is arranged on the inner surface of the stator,
Moreover, the conductor of the cylindrical rotor 21a is embedded in the outer surface side of the rotor, and the inner surface of the cylindrical stator 22a and the cylindrical rotor 21a are embedded.
The electric motor 23 for the internal fan 20 can be formed so as to face the outer surface of the internal fan 20. FIG. 5 shows another embodiment of the present invention, in which a pulley 24 is fixed to the back of the internal fan 20, an internal fan electric motor 23 is attached to the inside of the frame 2, and a shaft that can rotate together with the rotor in the electric motor 23 is shown. A pulley 26 is fixed to the internal fan 20 together with the pulley 24 via a toothed belt 27.
It is designed to rotate. FIG. 6 shows yet another embodiment of the invention, in which the internal air 14
One or more electric fans (two in the figure) are installed inside the frame 2 as means for circulating the internal fan.An internal fan electric motor 23 is installed inside the frame 2, and a In order to fix the internal fan 28 and to separate and rectify the air being blown and sucked, a cylindrical body 30 having a guide plate 29 inclined along the air flow 14 is installed concentrically with the motor rotating shaft 7. It is fixed to the fan electric motor 23. In the embodiments shown in FIGS. 5 and 6, similarly to the embodiment shown in FIG. 1, when the motor main body l stops, the internal fan motor 2
3 causes the internal fan 20.28 to rotate, and therefore both the external fan 5 and the internal fan 20.28 rotate, so
The stator 9 and the rotor IO1, as well as the stator winding 11 and the rotor conductor 12, are air-cooled to prevent melting and damage of the conductor 12. Further, in the embodiments shown in FIGS. 5 and 6, the internal fan electric motor 23 is attached to the outside of the frame 2, and only the shaft 25 is extended inside the frame 2, and the pulley 26 or the internal fan 28 is fixed to the tip thereof. You can do it like this. 7 and 8, a power transmission device 43 is disposed through the frame 2 of the main body electric motor 1, and the power transmission device 43 operates the internal fan 20 using the power of the external fan electric motor 4. This is an embodiment in which the internal fan can be rotated regardless of whether the electric motor 1 is stopped or operated at low speed. FIG. 7 shows a cup between the shaft 37 of the electric motor 4 of the external fan 5 and the intermediate ring 33 of a double bearing 31 consisting of an outer ring 32, an intermediate ring 33, and an inner ring 34 provided on the opposite load side of the frame 2 of the main motor l. By connecting the ring 36 and further connecting the other end of the intermediate wheel 33 facing the inside of the main body electric motor l and the back surface of the internal fan 20 with the coupling 35, the internal fan 20 is driven by the driving force of the electric motor 4 of the external fan 5. can be rotated. Since the outer ring 32 of the double bearing 31 is fixed to the frame 2 and the inner ring 34 is fixed to the rotating shaft 7, the internal fan 20
The rotation of the motor does not disturb the normal rotation of the rotor lO of the main motor 1. FIG. 8 shows an intermediate shaft 38 supported by a bearing 39 provided on the opposite load side of the frame 2 of the main motor 1, and a motor shaft 37 of the motor 4 of the external fan 5, connected to a pulley 40, 41 and a toothed belt 42. Connect via Furthermore, the intermediate shaft 38 and the internal fan 20 are connected via a pulley 24, 26 and a toothed belt 27. Since the internal fan 2G is rotatably mounted on the rotating shaft 7, it can be rotated arbitrarily by the driving force of the electric motor 4 of the external fan 5, regardless of whether the rotating shaft 7 is stopped or operating at low speed. It goes without saying that the present invention is not limited to the above-described embodiments, and that various changes can be made without departing from the gist of the present invention. [Effects of the Invention] According to the present invention, internal cooling is always ensured even when the all-gate fan type motor is stopped or operating at low speed, so rotor conductors are prevented from being melted and the next startup can be started in a short time. As a result, operating efficiency can be improved, and in the case of variable speed motors, it is not necessary to select a motor with a large output, and other excellent effects are exhibited.

[Brief explanation of the drawing]

Figure 1 is a sectional view of one embodiment of the present invention, Figure 2 0) (b)
and Fig. 3 ■ Baro) is a principle diagram of the generation of a rotating magnetic field in a two-pole three-phase flat stator, and Figs. FIG. 9 is a sectional view of the embodiment, FIG. 9 is a sectional view of a conventional device, and FIGS. In the figure, 1 is the main motor, 2 is the frame, 4 is the motor, 5 is the external fan, 20.28 is the internal fan, 21.21a is the rotor, 22.22a is the stator, 23 is the internal fan motor, and 31 is the internal fan. 37 is a motor shaft, 38 is an intermediate shaft, and 43 is a power transmission device.

Claims (1)

[Scope of Claims] 1) In a fully enclosed external fan-type motor in which an external fan for blowing air to the outer surface of the frame is provided on the outside of a frame forming the outer shell of the main motor, an electric motor for the internal fan is provided inside the frame. What is claimed is: 1. An internal cooling device for a totally enclosed external fan type motor, characterized in that an internal fan is provided for blowing air into the main body motor using the internal fan motor as a power source. 2) A motor for the internal fan is formed by fixing a rotor concentric with the fan to the back surface of the internal fan, and fixing a stator concentric with the rotor to the inside of the frame. An internal cooling device for a totally enclosed external sector electric motor according to claim 1. 3) In a fully enclosed external fan type electric motor in which an external fan for blowing air to the outer surface of the frame is provided on the outside of a frame forming the outer shell of the main motor, a power transmission device connected to the motor shaft of the external fan passes through the frame. 1. An internal cooling device for a completely enclosed external fan type motor, characterized in that an internal fan is provided which blows air into the main body motor using the external fan motor as a power source via the power transmission device.