JPH03173314A - Overheat preventing device for dynamo-electric machine - Google Patents

Abstract

PURPOSE:To protect winding and the like against overheat or burning due to overcurrent by short-circuiting the winding through a switch at the time of overload and operating a switch with the short circuit current thereby interrupting a power supply circuit. CONSTITUTION:When overcurrent flows due to overload and a winding 2 is heated over a predetermined temperature, a switch 11 closes to short-circuit a part of the winding 2. Such a switch 11 is disposed closely to the end of the winding where heat can be absorbed easily. The winding 2 is short-circuited through the switch 11 at the time of overload, and a switch 12 is operated with the short circuit current thus interrupting a power supply circuit. At this time, operating temperature and short circuit current of the switch 11 are set properly. By such arrangement, the power switch 12 is operated instantaneously and the winding 2 is protected reliably against overheat or burning due to overcurrent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an overheat prevention device that can reliably prevent overheating of a stator winding of a rotating electric machine.

[Conventional technology]

A conventional example of an overheating prevention device for a rotating electric machine will be explained based on FIG. 7. This figure shows the electrical circuit of a three-phase rotating electric machine, and U
A normally closed switch 1 is connected in series with the stator winding 2 in the phase and
When A2 reaches a high temperature above a certain value, the switch 1 opens to prevent the winding 2 from overheating.

[Problem to be solved by the invention]

In the above structure, the two switches 1 are not opened exactly at the same time during overload, so the rotating electric machine is operated in a momentary open-phase state, and in this state, a large open-phase current flows through the stator winding 2. If the open phase operation is repeated, the winding 2 may be overheated or burnt out. Also, the switch l cuts off a large current when overloaded, so repeating this will cause the contacts to fuse together.
The drawback is that it can cause damage.

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned drawbacks, it is an object of the present invention to provide an overheat prevention device for a rotating electric machine that can reliably prevent stator windings from overheating or burning out.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a stator winding 2
．． 21, 22, and 32 closes when the temperature reaches a certain level or higher due to excessive current, and in a three-phase rotating electrical machine, part or all of the winding 2 is closed, and in a single-phase rotating electrical machine, the starting switch 34 is closed.
Alternatively, it is provided with a bimetallic switch 11 that short-circuits the capacitors 23 and 33, and a manual return switch 12 that opens the circuit with the short-circuit current and interrupts the power supply circuit.

[Effect]

In the event of an overload, the switch 11 short-circuits the winding 2, etc., and the short-circuit current operates the switch 12 to cut off the power supply circuit, so the operating temperature of the switch 11 and the short-circuit current can be set appropriately. By doing so, the power switch 1 is instantly turned off.
2, it is possible to reliably prevent overheating or burnout of the winding 2 etc. due to excessive current. The switch 11 is a bimetallic type and automatically returns to the original open state when the temperature of the winding 2, etc. drops below a certain value, but at this time there is no voltage, so there is no damage to the contacts. Even if the switch 11 is automatically reset, the power switch 12 is of a manual reset type, so unless it is turned on again, the rotating electric machine will not suddenly restart after being stopped due to overload or the like.

〔Example〕

1 to 3 show embodiments of this invention,
Components indicated by the same reference numerals as in FIG. 7 are the same parts. These figures show a three-phase rotating electric machine and its electric circuit, in which a stator core 14 is fitted into the inner periphery of an axially long cylindrical frame 13, and a box-shaped handle 15 is connected to one end of the frame 13. It is set up. The iron core 14 has three-phase stator windings 2.
In the case shown in FIG. 2, a bimetal type automatic return type switch 11 is connected in parallel with a part of the U-phase winding 2. This switch 11 is used to close a circuit and short-circuit a part of the winding 2 when the winding 2 reaches a high temperature above a certain value due to excessive current flowing due to an overload, etc., and absorbs the heat generated by the winding 20. It can be easily installed near the end of the winding. The lead wires of the windings 2 of each phase are connected to the power supply via cables 16, and the power supply circuits of the U and V phases are manually reset by opening the circuit with the short-circuit current caused by the operation of the switch 11 and cutting off the power supply circuit. A type switch 12 is installed within the handle 15 and connected thereto. In the switch shown in FIG. 3, a switch 11 having a built-in heater 17 is connected in parallel with the entire U-phase winding 2, and in this case, the position of the switch notch 11 is not restricted by the action of the heater 17.

Figures 4 to 6 showing other different embodiments are electrical circuit diagrams of a single-phase rotating electric machine, and in Figure 4 showing a capacitor-operated rotating electric machine, an auxiliary winding 21 and a capacitor 2 are connected in series.
3 is connected in parallel with the main winding 22, and the short-circuit switch 11
is connected in parallel with the capacitor 23. 5 and 6 show a capacitor-start type rotating electric machine, in which an auxiliary winding 31 connected in series, a starting switch 34 that is opened during operation, and a capacitor 33 are connected in parallel with the main winding 32, and the starting switch 34 and capacitor 33
A short-circuit switch 11 is connected in parallel with the short-circuit switch 11 in FIG. 5, and a switch 11 with a current-limiting reactor 35 is connected in FIG. In a split-phase rotating electric machine (not shown), a short-circuit switch 11 is connected in parallel to the starting switch connected in series with the auxiliary winding.
is connected.

According to the embodiment, the switch 11 is turned on when the load is overloaded.
Since the iA2 etc. are short-circuited and the short-circuit current operates the switch 12 to cut off the power supply circuit, the power supply switch 12 can be instantaneously operated by appropriately setting the operating temperature of the switch 11 and the short-circuit current. This makes it possible to reliably prevent overheating or burnout of the winding 2 and the like due to excessive current. The switch 11 is a bimetallic type and automatically returns to the original open state when the temperature of the winding 2, etc. drops below a certain value, but at this time there is no voltage, so there is no damage to the contacts. Even if the switch 11 is automatically reset, the power switch 12 is of a manual reset type, so unless it is turned on again, the rotating electric machine will not suddenly restart after being stopped due to overload or the like.

In the embodiment described above, a case has been described in which an axially long frame 13 and a box-shaped handle 15 are used, but the present invention is not limited thereto.

〔Effect of the invention〕

According to this invention, in an overheat prevention device for a rotating electric machine, when an overload occurs, a bimetal type automatic reset type switch short-circuits the stator windings, etc., and the short-circuit current is used to operate a manual reset type switch to power the power supply. Since the circuit is cut off, by appropriately setting the operating temperature and short-circuit current of the short-circuit switch, the power switch can be activated instantly to reliably prevent windings from overheating or burning out due to excessive current. Furthermore, it is possible to prevent damage to the contact portion of the short-circuit switch.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of an embodiment of the invention, FIG. 2 is an electric circuit diagram of FIG. 1, FIGS. 3 to 6 are electrical circuit diagrams of other embodiments of the invention, and FIG. is an electrical circuit diagram of a conventional example. 2.21, 22.32... Winding, 11... Switch, 12... Switch, 23.33... Capacitor, 3
4...Chan drawing diagram item ■

Claims (1)

[Claims] 1) When the stator winding reaches a high temperature above a certain value due to excessive current, it closes and closes part or all of the winding in a three-phase rotating electrical machine, and the starting switch or (and) capacitor in a single-phase rotating electrical machine. A short-circuiting bimetallic switch,
An overheat prevention device for a rotating electric machine characterized by comprising a manual reset type switch that opens the circuit with this short-circuit current and interrupts the power supply circuit.