JPH07119595A - Controller for start of motor - Google Patents

Abstract

PURPOSE:To accurately and surely control the start of motor without restriction from the temperature increase allowable value of the motor by computing the present temp. of motor and predictingly computing whether the temp. exceeds the allowable temp. at the time of next start or not. CONSTITUTION:The current of motor detected by a current transformer 15 for a mesuring device is input to a start current/start time detector 3 and a temp. increase computing device 4. Outputs of the opening contact of a start switch 14 and constant settor 5 are input to a temp. decrease computing device 6. Namely, the temp. of motor is computed through the time of operation and the time of stop and the current of the motor. The allowable temp. specified for every kind of motors and the temp. rise when start is made again are compared with the results of prediction cumputation. Judgement is made whether the temperature of motor is lower than the level to enable the start-up to carry out the start control of the motor. It is thus possible to prevent operation error which leads to temp. increase over the allowable level by repetition of the start/stop and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suitable starting control device for an electric motor in an electric equipment composed of the electric motor and its starter.

[0002]

2. Description of the Related Art Except for special motors such as inching operation specifications, most general electric motors are designed to be able to start twice in a cold state and once in a hot state. ， Operating control is performed by accurately grasping the temperature according to the operating state of the motor, because the operator judges whether it is in the hot state based on the standard of the required cooling time (stop time) presented by the manufacturer. However, there is a problem that the cooling time is unnecessarily lengthened, and conversely, the cooling time is short and the electric motor is burnt out.

[0003]

Although it is possible to measure the temperature of an electric motor by using a resistance temperature detector or the like, these measurements cannot be immediately measured due to the time constant, so that the conditions for starting control cannot be met. It cannot be used. In addition, there is a drawback that the electric motor has a special design because it needs to be embedded in the electric motor itself.

[0004]

[Means for Solving the Problems] Results of predictive calculation of an electric motor temperature from operating and stopping times and an electric motor current, and an allowable temperature determined for each type of electric motor and a temperature rise when starting again. Are compared to determine whether or not the temperature is equal to or lower than the temperature at which the electric motor can be started, and start control of the electric motor is performed.

[0005]

According to the present invention, the electric motor starting control which is restricted by the allowable temperature rise value of the electric motor can be accurately and surely performed.

[0006]

Embodiments of the present invention are shown in FIGS. 1 and 2.

FIG. 1 is a block diagram of a power supply facility and a start control device.

The motor current detected by the instrument current transformer 15 is connected to the analog / digital converter 2, and its output is input to the starting current / starting time detector 3 and the temperature rise calculator 4. The output of the constant setter 5 for setting a constant that differs depending on the closed contact of the start switch 14 and the type of the electric motor is also input to the temperature rise calculator 4.

The open contact of the starting switch and the output of the constant setting device 5 are input to the temperature decrease calculator 6. With respect to the temperatures calculated by the temperature increase calculator 4 and the temperature decrease calculator 6, an adder 7 calculates the motor temperature.

The output of the predictive calculator 8 for calculating the temperature rise at the time of start by the output of the adder 7 and the output of the starting current / starting time detector 3 is added by the adder 9 and input to the temperature setter 10 to be added. Compare the value with the allowable temperature setting. When the value is less than or equal to the set value, the start permission command is output, and when the value is greater than or equal to the set value, the start non-permission command is output to control the start of the motor 16.

FIG. 2 shows an interlock diagram.

When the start permission command output 11 from the start control device is transmitted when the operation switch 17 is turned on, when the switch 14 is closed and the motor can be started and the start non-permission output 12 is transmitted. Warns the operator by giving an alarm.

FIG. 3 shows an example of the relationship between temperature rise and time when the electric motor is started.

When the electric motor in the cold state is started, the temperature rapidly rises due to the heat generated by the starting current, but by continuing the normal operation after the completion of the start, the temperature gradually decreases and becomes a stable temperature. Further, when restarted in the hot machine state, the temperature becomes higher than that in the cold state and the time required to reach the stable temperature becomes longer.

The magnitude of the temperature rise and fall depends on the current and run /
It can be calculated based on the product of stop times.

[0016]

As described above, according to the present invention, it is possible to prevent an inadvertent operation that causes a temperature rise that exceeds the allowable temperature of the electric motor due to repeated start / stop of the electric motor.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a power supply facility and a start control device.

FIG. 2 is an operation interlock diagram of the electric motor.

FIG. 3 is a diagram showing a relationship between temperature rise and time when the electric motor is started.

[Explanation of symbols]

1 ... Starting control device, 2 ... Analog / digital converter, 3
… Starting current / starting time detector, 4… Temperature rise calculator, 5
... Constant setter, 6 ... Temperature decrease calculator, 7,9 ... Adder,
8 ... Prediction calculator, 10 ... Temperature setter, 11 ... Start permission command output, 12 ... Start non-permission output, 13 ... Power bus, 14
... Switch, 15 ... Current transformer for instrument, 16 ... Electric motor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideyoshi Kitami 3-2-1, Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Engineering Co., Ltd.

Claims (1)

[Claims] 1. In an electric facility comprising an electric motor and a starter for starting the electric motor, the electric motor temperature calculated based on the electric motor operation and stop time, electric motor current, etc.,
An electric motor start control device, which performs a comparison calculation with an allowable temperature setter of an electric motor to determine whether the electric motor can be started and issues a start permission command for the electric motor.