JPH0614583A - Protective method for commutatorless motor - Google Patents

Abstract

PURPOSE:To provide a protective method for commutatorless motor in which current flowing into the commutatorless motor is limited without requiring any current detector including a CT while simplifying the circuitry of protector. CONSTITUTION:When a predetermined voltage is fed to a predetermined stator winding of a commutatorless motor and the rotational frequency thereof is controlled to a target value, current I flowing into the commutatorless motor is estimated (Step ST1) based on a relationship between a voltage(V) to be fed to the stator winding and a current rotational frequency(f) obtained from positional information fed from a rotor position detecting means, the current I thus estimated is compared with a limit current value and a release current value(Step ST2, ST4), and a supply voltage to the stator winding is controlled at a predetermined level based on the comparison result. If the current I exceeds the limit current value, supply voltage to the stator winding of commutatorless motor is lowered by a predetermined value (Step ST3) thus suppressing current flowing into the commutatorless motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for protecting a commutatorless motor (brushless motor) used in various devices.

[0002]

2. Description of the Related Art Conventionally, a commutatorless motor of this type supplies a predetermined voltage to a predetermined stator winding based on the position of a rotor (rotor) and also supplies a predetermined voltage to the predetermined stator winding. It is driven at an arbitrary rotation frequency by changing it.

When the non-commutator motor is used as a motor for a compressor of an air conditioner, for example, when the air conditioner is overloaded, the rotational frequency of the commutator motor is set to a target value. Since the voltage supplied to the predetermined stator winding of the same commutator motor increases, the current flowing into the same commutator motor increases, and more current than necessary may flow into the same commutator motor.

Therefore, there are restrictions on the flaker and the power cable, and in order to protect the non-rectifier motor, a current detecting means (including CT) is provided at a predetermined position of the air conditioner,
The voltage supplied to the predetermined stator winding of the same commutator motor is varied based on the value detected by the current detection means to limit the current flowing into the same commutator motor.

[0005]

By the way, the above method of protecting a commutatorless motor requires current detecting means including the CT, that is, a large number of parts and circuits, which is an air conditioner. (System) cost is high.

The present invention has been made in view of the above problems, and an object thereof is to estimate a current of a non-rectifier motor without using a current detecting means including a CT or the like and to flow a current into the non-rectifier motor. It is therefore an object of the present invention to provide a method for protecting a non-commutator electric motor, which can reduce the cost of the protection device (system (air conditioner or the like)) for the non-commutator electric motor.

[0007]

In order to achieve the above object, a method for protecting a non-commutator motor according to the present invention detects a position of a rotor of a non-commutator motor and based on the detected position. When supplying a predetermined voltage to a predetermined stator winding of the same non-commutator motor and varying the predetermined voltage to control the rotor of the non-commutator motor to a target rotation speed,
The current flowing into the non-commutator motor is calculated from the relationship between the voltage supplied to the stator winding of the non-commutator motor and the rotation frequency of the rotor obtained from the position information of the rotor position detection means. The gist is that the voltage supplied to the predetermined stator winding can be varied according to the calculated current value to limit the current of the non-commutator motor.

[0008]

With the above method, the current flowing into the non-rectifier motor is estimated by the voltage supplied to the predetermined stator winding of the non-rectifier motor and the rotation frequency based on the rotor position information. That is, the rotation frequency of the non-commutator motor is determined by the voltage supplied to the stator.

The estimated current, that is, the estimated current is compared with the limiting current value and the release current value (preset value) of the non-rectifier motor, and the comparison result shows the non-rectifier motor. The voltage supplied to the predetermined stator is varied, and, for example, when the current flowing into the non-rectifier motor exceeds the limit current value, the voltage supplied to the stator is reduced by a predetermined value.

As described above, the current flowing into the non-rectifier motor can be estimated and the protection control of the non-rectifier motor can be performed without using a current detection device including CT or the like. It is possible to simplify the circuit for reducing the cost.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for protecting a commutatorless motor according to the present invention is a method for supplying a current value flowing into the commutatorless motor to a predetermined stator winding of the commutatorless motor and a rotational frequency of the commutatorless motor. It is presumed from the above that the current of the same commutator motor is limited, and the circuit of the current detecting means including CT and the like is not required.

Therefore, for example, the case of application to the air conditioner shown in FIG. 2 will be described. In this air conditioner, the AC voltage of the commercial power source 1 is converted into a DC voltage by the AC / DC voltage converter 2. , This DC voltage is converted into AC / DC converter 3
Is converted into an alternating current (predetermined frequency) and supplied to a predetermined stator winding of the commutatorless motor (motor) 4 of the compressor.

The position of the rotor of the non-commutator motor 4 is determined by a rotor position detecting circuit (position detecting means) 5
The position detection signal of the rotor is input to the control device (microcomputer) 6 of the air conditioner, and the microcomputer 6 controls the DC / AC converter 3.

In this case, for example, the input DC voltage level of the DC / AC converter 3 is variably controlled so that the rotation frequency of the non-commutator motor 4 becomes a target value, and the varied DC voltage is changed. Based on the position detection signal from the rotor position detection circuit 5, it is supplied to a predetermined stator winding of the non-commutator motor 4. As a result, the rotation of the commutatorless motor 4 is controlled to the target value.

Next, the method of protecting the commutatorless motor of the present invention will be described in detail with reference to the flow chart of FIG. 1. First, the microcomputer 6 controls the commutatorless motor 4 of the compressor. The rotation frequency of the commutator motor 4 is set to a target value.

At this time, in the microcomputer 6, the DC / AC converter 3 is controlled according to the operating frequency of the compressor, and the output voltage level of the DC / AC converter 3 is changed. The output voltage level (V) is already known, and the current operation frequency (rotor rotation frequency; f) of the compressor is known from the position detection signal from the rotor position detection circuit 5.

Here, the current I flowing into the commutatorless motor 4 is calculated by I = k (V / f) (step ST1). Since k in the above equation is used for conversion when calculating the current from the voltage V and the rotation frequency f,
It is a constant preset according to the characteristics of the non-commutator motor. The formula for calculating the current will be described. Since the rotation frequency of the non-rectifier motor is determined by the voltage supplied to the stator, the voltage (V) supplied to the stator and the rotation frequency (f The current flowing into the commutatorless motor can be estimated by the ratio of

Subsequently, it is judged whether or not the calculated current I by the above I = k (V / f) equation exceeds a predetermined limit current value (step ST2), and the calculated value I is calculated.
Exceeds the limit current value, that is, when the load of the air conditioner increases due to some reason and the current flowing into the non-rectifier motor 4 is larger than usual, the output voltage of the DC / AC converter 3 is increased. Control is performed to reduce the level by a predetermined value. As a result, the operating frequency of the compressor is reduced by a predetermined value, so that the current flowing through the commutatorless motor 4 is suppressed.

On the other hand, when the calculated current I does not exceed the limit current value, the process proceeds from step ST2 to ST4, and the calculated current 1 has a preset release current value (value lower than the limit current value by a predetermined value). It is determined whether or not the following. When the calculated current I is not equal to or less than the release current value, that is, the current of the commutatorless motor 4 reduced by the process of step ST3 is checked, and, for example, the current flowing into the commutatorless motor 4 is limited to the limit. When the current value is less than or equal to the current value but greater than the release current value, control for maintaining the output voltage level of the DC / AC conversion unit 3 is executed (step ST5).

Subsequently, when the calculated current I is equal to or less than the release current value, the process proceeds from step ST4 to ST6, and the compressor is operated normally. That is, the output voltage level of the DC / AC converter 3 is controlled so that the operating frequency of the compressor (rotating frequency of the rotor) becomes the target value in the air conditioner.

In this way, the voltage (V) for supplying the current flowing into the commutatorless motor 4 of the compressor to the stator winding of the commutatorless motor 4 and the position information of the rotor of the commutatorless motor 4 are obtained. Since it is obtained by the rotation frequency (f) of the stator, a current detection device including CT is not required, and the stator is obtained by the comparison result of the obtained calculated current value I and the limiting current value or the release current value. Since the voltage supplied to the windings is controlled, the current flowing into the non-rectifier motor can be suppressed, the circuit of the protection device for the non-rectifier motor can be simplified, and eventually the air conditioner. It is possible to reduce the cost.

[0022]

As described above, according to the method for protecting a commutatorless motor of the present invention, the position of the rotor of the commutatorless motor is detected and the commutatorless motor is detected based on the detected position. When a specified voltage is supplied to the specified stator winding of the slave motor and the specified voltage is varied to drive the rotor of the same commutator motor at the target rotation speed, the current flowing into the same commutator motor is adjusted. Calculated by the voltage supplied to the stator winding and the rotation frequency obtained from the position information of the rotor position detecting means, and the calculated current value is compared with the limiting current value and the release current value, and based on this comparison result. Since the voltage supplied to the predetermined stator winding is varied to limit the current of the non-commutator motor, a current detection device including CT for obtaining the current flowing into the non-rectifier motor is Without The current that flows into the non-rectifier motor can be suppressed, that is, it can be kept within the constraints of the breaker and power cable to protect the non-rectifier motor, and the circuit configuration of the protection device can be simplified to reduce costs. There is a useful effect that can be.

[Brief description of drawings]

FIG. 1 is a schematic flow chart diagram explaining an operation of a method for protecting a commutatorless motor according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram of an air conditioner to which an embodiment of the present invention is applied and to which a method for protecting a commutatorless motor is applied.

[Explanation of symbols]

 1 Commercial power supply 2 AC / DC voltage conversion unit 3 DC / AC conversion unit 4 Non-commutator motor (compressor motor) 5 Rotor position detection circuit (position detection means) 6 Controller (microcomputer)

Claims (1)

[Claims] 1. A position of a rotor of a non-commutator motor is detected, a predetermined voltage is supplied to a predetermined stator winding of the same commutator motor based on the detected position, and the predetermined voltage is supplied. To control the rotor of the non-commutator motor to a target rotational speed by varying the voltage, the voltage supplied to the stator winding of the non-commutator motor and the position information obtained by the position detection means of the rotor. Due to the relationship with the rotation frequency of the rotor,
The current flowing into the non-rectifier motor is calculated, and the voltage supplied to the predetermined stator winding is varied based on the calculated current value, so that the current of the non-rectifier motor can be limited. How to protect commutatorless motors.