JPH09308090A - Motor restraint protection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge whether an AC motor is under starting acceleration or restraint for restraint protection of the motor by detecting the restraint condition of the motor by the operation of a wind pressure relay which is fitted inside an external fan cover and detects wind pressure generated by an external fan. SOLUTION: If an AC motor 30 is in a restraint condition with a breaker 21 closed and the AC motor 30 turned on, the contact 18b of a wind pressure relay is kept closed, and voltage is applied to a timer 24 through an auxiliary contact 21a. When setting time which is previously-set shorter than the allowable restraint time of the AC motor passes, the timer 24 comes into action, and a time contact 24a closes (ON), a trip coil 21T is energized so as to come into action, thus tripping the breaker 21. When the AC motor 30 is in a restraint condition, the breaker 21 closes in operating time shorter than the allowable restraint time by the contact 18b and the timer 24, and the AC motor 30 is stopped, thus providing restraint protection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor restraint protection device.

[0002]

2. Description of the Related Art Conventionally, in order to detect a restrained state of a rotating electric machine such as an AC electric motor, an overcurrent relay (relay) is connected to an AC circuit as a power source, and the current value increases in the restrained state. Had detected that.

Therefore, when the load of the AC motor is large, it is difficult to distinguish whether the increase in the current value is due to the restrained state or whether the load is simply large. That is, when using the AC motor having the temperature curve (temperature characteristic curve) C of the AC motor, the load GD ² (moment of inertia) is the allowable GD of the AC motor.
When it is larger than ² , as shown in FIG. 3, the AC motor starting current curve A becomes larger (takes time) than the allowable constraint time B, and therefore has an overcurrent relay operation characteristic curve D for protecting the AC motor. The overcurrent relay had a problem that it was not possible to perform restraint protection.

[0004]

SUMMARY OF THE INVENTION The present invention provides an electric motor restraint protection device which can reliably determine the restrained state of an electric motor by providing a wind pressure relay for detecting a change in wind pressure caused by the electric motor rotor. Is intended.

[0005]

SUMMARY OF THE INVENTION An electric motor restraint protection device of the present invention includes an air passage installed around a stator of an electric motor for passing cooling air, and an electric motor installed by rotating a rotating shaft of the electric motor to rotate the electric motor. An external fan that cools from the outside, an external fan cover that houses the external fan and is connected to the air passage, a wind pressure relay that is installed inside the external fan cover and that detects the wind pressure generated by the external fan, and an electric motor that operates by the wind pressure relay. And a motor restraint protection circuit for detecting the restrained state of and protecting the motor.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of a motor restraint protection device of the present invention will be described. In FIG. 1, a motor has a shaft 9 rotatably attached to a stator frame 1 via a bearing bracket 6 and a bearing metal 7, and an oil ring 8 is provided on the bearing metal 7 and is sent from an oil supply pipe 16 for use. The lubricated oil thus removed is discharged through the oil drain pipe 17.

Further, the rotor core 10 has a rotor bar 1
2 and a short circuit ring 13 are attached. It is cooled by the inner fan 5 attached to the shaft 9. The windbreak plate 4 is for controlling the ventilation direction of the cooling air.

The stator winding 3 is provided so as to face the rotor core 10, and is cooled by a cooling air flow 20 passing through an air passage 11 attached to the periphery of the stator. Outside fan 1
4 is attached to a shaft (rotary shaft) 9 of the electric motor, and cools the electric motor from the outside by a wind flow 20 generated by the rotation of the shaft 9. The outer fan cover 15 accommodates the outer fan 14 and is connected to the air passage 11 to guide a wind flow 20.
The wind pressure relay 18 is a device that is installed inside the outer fan cover 15 and detects the wind pressure generated by the outer fan 14.
Shows an example of an electric motor restraint protection circuit that detects the restrained state of the electric motor by the operation of the wind pressure relay 18 and protects the electric motor.

That is, the electric motor restraint protection circuit shown in the figure comprises an AC electric motor 30 and an electric motor board 20A.
0 is provided with a contact point 18b of a wind pressure relay 18 which opens a circuit by the wind pressure generated when the AC electric motor 30 is started and rotated.

The motor board 20A has a circuit breaker 21 for opening and closing the main circuit of the AC motor 30, and a circuit breaker 21.
The current transformer 22 is connected in series with the current transformer 22, and an overcurrent relay 23 is connected to the secondary side of the current transformer 22.

The auxiliary contact 21a is a contact that is closed when the circuit breaker 21 is turned on. When the circuit breaker 21 is turned on, the overcurrent relay 23 operates to contact the contact 23a.
Is closed, the auxiliary relay 25 connected between the positive bus P and the negative bus N is excited to operate, and the contact 25a is closed. Then, the trip coil 21T which trips the breaker 21 to open the circuit. Is excited and operates, and the circuit breaker 21 is tripped.

Next, the operation of the wind pressure relay 18 will be described. When the breaker 21 is closed and the AC motor 30 is powered on, if the AC motor 30 is in the restrained state, the contact 18b of the wind pressure relay 18 remains closed, and the auxiliary contact 21a is used. Voltage is applied to the timer 24. Then, when a preset time shorter than the allowable constraint time of the AC motor 30 has elapsed, the timer 2
4 operates, the time contact 24a is closed (ON), the trip coil 21T is excited, and the breaker 21 trips.

FIG. 3 is a diagram showing the allowable restraint protection of the AC motor 30. The overcurrent relay operating characteristic curve D for protecting the AC motor is set to be smaller than the thermal curve (temperature characteristic curve) C of the AC motor 30. The operating time E by the timer 24 is set to be shorter than the allowable constraint time B.

That is, when the AC electric motor 30 is in the restrained state, the breaker 21 is opened by the contact 18b of the wind pressure relay 18 and the timer 24 in the operation time E shorter than the allowable restraint time B of the AC electric motor 30 to open the AC electric motor 30. Restraint protection can be provided by stopping.

As described above, according to this embodiment, the wind pressure relay provided in the AC motor can determine whether the AC motor is in starting acceleration or in restraint, so that the restraint protection of the AC motor is performed. be able to.

[0016]

According to the present invention, the operational safety of the motor restraint protection device can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electric motor restraint protection device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an embodiment of a motor constraint protection circuit.

FIG. 3 is an explanatory view showing the operation of FIG.

[Explanation of symbols]

 1 Stator Frame 2 Stator Iron Core 3 Stator Winding 4 Windbreak Plate 5 Inner Fan 6 Bearing Bracket 7 Bearing Metal 8 Oil Ring 9 Shaft 10 Rotor Iron Core 11 Airway 12 Rotor Bar 13 Short Circuit Ring 14 Outer Fan 15 Outer Fan Cover 16 Oil supply pipe 17 Oil discharge pipe 18 Wind pressure relay 20 Wind flow

Claims (1)

[Claims] 1. An air passage installed around a stator of an electric motor for passing cooling air; an external fan attached to a rotating shaft of the electric motor to cool the electric motor from the outside by rotation of the rotating shaft; and an external fan. An external fan cover that accommodates the air passage and is connected to the wind passage, a wind pressure relay that is installed inside the external fan cover and that detects the wind pressure generated by the external fan, and the operation of the wind pressure relay detects the restrained state of the electric motor. And a motor restraint protection circuit that protects the motor.