WO2015139713A1

WO2015139713A1 - Method for operating a motor

Info

Publication number: WO2015139713A1
Application number: PCT/EP2014/002271
Authority: WO
Inventors: Hartmut Wauer; Rainer Frisch
Original assignee: Diehl Ako Stiftung & Co. Kg
Priority date: 2014-03-20
Filing date: 2014-08-19
Publication date: 2015-09-24

Abstract

The invention relates to a motor of an electrical device, in particular of an electrical domestic appliance, which has an absolute power limit (P.limit), above which the motor cannot be operated without being damaged, and a nominal power (P.max), which lies below the absolute power limit (P.limit) and at which the motor can be continuously operated without being damaged. In the case of an elevated power requirement (P.required) that lies above the nominal power (P.max) of the motor, the motor can be operated at an elevated power (P.incr) in a boost mood to a limited extent, which elevated power lies above the nominal power (P.max) by an additional power (P.boost) but does not exceed the absolute power limit (P.limit).

Description

Method of operating an engine

The present invention relates to a method for operating a motor of an electrical device, in particular a household electrical appliance.

Engines in newer electrical appliances, such as washing machines or other household electrical appliances, are preferably powered by frequency converters. The power limit of the overall system is determined by the voltage and current limits of the electronic components, in particular the power section and the rectifier for the intermediate circuit, as well as the heating of the motor and the electronics. In order for the electronics to be able to meet a required minimum service life, the performance limits are usually not fully exhausted; instead, for example, a percentage security is included.

In frequency converters of recent design, for example, a fixed power limit is set, which corresponds to the maximum possible continuous power at which the electronics and the motor do not sustain permanent damage (so-called nominal power). When this power limit is reached, the control parameters are usually changed in such a way that exceeding this upper power limit is permanently avoided, e.g. by withdrawing the setpoint speed until the power limit is maintained again. This mode of operation in the event of an imminent overload is called "Reduce Mode." In the event of a sustained overshoot, a kind of "tampering" can be activated, which reduces the engine speed, for example. set to zero to avoid damaging the electronics and motor. In conventional systems or engine controls there is no assessment of the overload case. The set power limit is rather a hard limit.

The object of the invention is to provide an improved method for operating a motor, with which the performance of the electrical device can be increased. In particular, the electrical device to a limited extent

CONFIRMATION COPY can also handle overloads that require increased engine power beyond the nominal horsepower of the engine.

This object is achieved by a method for operating an electrical device having the features of claim 1. Particularly preferred refinements and developments of the invention are the subject of the dependent claims.

The motor of an electrical appliance has an absolute power limit from which it can not be operated without being damaged, and a nominal power which is below the absolute power limit and with which it can be operated permanently without being damaged , In the method of operating the motor according to the invention, in the case of an increased power requirement that is above its nominal power, the motor is operated to a limited extent in a boost mode with an increased power which is an additional power above the nominal power, but does not exceed the absolute performance limit.

According to the invention, the motor of the electrical device can be operated to a limited extent with an increased power (boost mode), which is above its nominal power for permanent operation. As a result, the electrical device can also manage, at least to a limited extent, overload cases (more than 100% of the nominal power) (in the case of a washing machine, for example, during a spin cycle) and thus improve its performance.

The present invention is basically applicable to all electrical devices with a motor. Preferably, the method according to the invention is used in household electrical appliances such as laundry treatment equipment (e.g., washing machines, clothes dryers, etc.), dishwashers, and the like.

The present invention is based on the following considerations.

Since the electronics and motor are not designed to reach their maximum power limit, there are "reserves" in the design of the electronic components as well as in the engine, which is also called "safety". Critical load cases, such as overcurrent, overvoltage and excessively high temperatures in motor and electronics are already being protected by protective functions. This ensures that the electronics are not overloaded life-shorteningly at their discretion over the entire service life. The inventors have recognized that exceeding the hard load limit (nominal power of the motor) can be permitted to a limited extent, as long as the overload does not permanently damage (damage) electronic components. The concept of the invention assumes that a power over a certain time corresponds to an energy equivalent, which causes a certain heating in the electronics and in the engine. As a rule, so-called thermal models which take into account both power supply and cooling can be used for the calculation. Boost mode allows increased power draw above the normally allowed power limit (nominal power) but still within absolute limits. This increased power consumption must be limited, so that no (pre-) damage to the engine electronics occur in this special case. If the increased power is no longer retrieved, it can be assumed that the temperature on the electronics drops back to a permanently loadable range over a predeterminable time constant.

This results in a process for the dynamic provision of additional energy components. For periods in which the instantaneous power is greater than the maximum permissible continuous power, for example, that part of the power per unit of time that exceeds the maximum permissible continuous power is added up. If this sum value reaches a predefined amount of power, the engine electronics returns to the old procedure of a rigid maximum power limit and remains until the previously accumulated power total has been completely reduced again by a predetermined method. Alternatively, the system may remain at this fixed power limit until a predefined time has passed or the engine electronics are restarted. If the maximum permissible power limit is reached again before reaching the maximum power amount, the power sum accumulated up to that point is reduced again according to a predefined method. In the simplest case, a predefined amount of power is subtracted from the power sum per unit of time (linear degradation). Other methods, in particular complex mathematical models describing the thermal behavior of the engine, are also conceivable. This results in a performance limit for the operation of the motor, which may be exceeded dynamically for a short time and recurrently. The summation of the surplus power and the comparison with a predefined power amount can ensure that neither the electronics nor the motor are permanently damaged.

An advantage of the method according to the invention is that a boost mode can be made available to the electrical device, for example a washing machine, beyond the limit of a permanently set maximum power, which can significantly improve the performance of the device, for example the wash result a washing machine, especially when spinning. The electrical device, such as a washing machine, thus behaves "good-natured" against short-term overloads.

In accordance with the present invention, limited and defined increased motor power may be provided instead of a normally hard set power limit (nominal power) to protect the motor and electronics. The ability to temporarily and controllably exceed a normally predefined performance upper limit results in advantages in device performance, especially when spinning (dehumidifying the laundry) in a washing machine. Boundary cases in which performance drops due to reaching the performance limit can be cushioned without jeopardizing the safety of the machine.

In a preferred embodiment of the invention, the operation of the engine in the boost mode is limited in terms of performance.

For this purpose, the additional power during operation of the motor in boost mode is preferably added up and the boost mode is ended when the additional power sum exceeds a predetermined maximum additional power sum.

In a further preferred embodiment of the invention, the operation of the engine in the boost mode (in addition to or as an alternative to the power limitation) is limited in time.

In yet another preferred embodiment of the invention, the boost mode for the operation of the engine is only available if an additional sum of power previous operations of the engine in boost mode has been at least partially degraded again. The reduction of the additional power sum, for example, via a cooling of the electronics and the engine. Preferably, the boost mode for the operation of the engine is made available only after a predetermined period of time has elapsed since a last operation of the engine in boost mode. This predetermined period of time is preferably fixed or is calculated as a function of the additional power sum of previous operations or a last operation of the engine in boost mode.

Alternatively or additionally, the boost mode for the operation of the engine is preferably provided only if a difference between a predetermined maximum additional power sum and an optionally at least partially reduced additional power sum of previous operations of the engine in the boost mode exceeds a predetermined differential value , In other words, the motor is preferably operated again in boost mode only when there is (again) sufficient buffer for operation with the increased power.

In another preferred embodiment, the boost mode for the operation of the engine is available only once after the engine has been switched on. This variant assumes that the electronics and the engine can cool down sufficiently (only) after switching off the engine so that the boost mode can be made available again when the engine is restarted. The invention also relates to a control device for operating an engine according to the method of the invention described above.

The invention also relates to an electrical device, in particular a household electrical appliance, with a motor which is operated according to the method of the invention described above.

The above and other features and advantages of the invention will become more apparent from the following description of a preferred, non-limiting embodiment thereof with reference to the accompanying drawings. In it show, in part schematically: 1 is a flowchart of a flow of a method for operating a motor according to an embodiment of the invention; and

FIG. 2 is a power-time diagram illustrating the operation of the method of FIG. 1. FIG.

The method according to the invention for operating a motor of an electrical device is explained in more detail below using the example of an operating method for an electric motor of a drum of a washing machine. ^"

The electric motor has a nominal power P.max, up to which it or its control electronics can be operated permanently without being damaged. The nominal power P.max is usually determined by the manufacturer and noted in the data sheet of the motor. In conventional systems, this nominal power P.max is used as a hard limit which must not be exceeded. In addition, the electric motor has an absolute power limit P.limit, which must not be exceeded, not even for a short time. The absolute power limit P.limit is greater than the nominal power P.max, for example, it is about 2 to 10% larger. After the electric motor is switched on in step S100, the power P.required picked up by the engine is continuously measured during the washing program and compared with the nominal power P.max of the motor in step S110. If the limit of the nominal power P.max is not exceeded by the current power demand P.required of the engine (YES in S110), the engine is operated in the normal operation mode (step S120) and with a power P = P.required less than or equal to the nominal power P.max supplied.

If it is determined in step S1 10 that the current power demand P.required of the motor exceeds, for example, a nominal power P.max due to an overload case during a spin operation (NO in S110), the flow proceeds to step S130, where testing is performed whether a Boost mode is currently available for the operation of the engine. The test as to whether the Boost mode is available at the current time or operating state of the engine is explained in more detail below. If it is determined that - for whatever reason - no Boost mode is available (NO in S130), the engine will become - as with conventional systems - "Reduce Mode" and operated at a power corresponding to the nominal power (P = P.max) as the power limit, to prevent the motor or its electronics from being damaged (step S140), but if it is determined in step S130, that the boost mode is available (YES in S130), the flow advances to step S150 In this step S150, the actual power demand P.required is compared with the motor absolute power limit P.limit If the current power demand P .required is below the absolute power limit (NO in S150), the motor is operated in step S160 with an increased power P.incr which is greater than the nominal power P.max and which corresponds to the actual power demand P.required Power requirement P.required reached the absolute power limit (YES in S150), the motor is operated in step S170 with an increased power P.incr, which is the absolute power limit P.limit corresponds. In any case, the increased power P.incr is an additional power P.boost greater than the nominal power P.max of the motor (P.incr = P.max + P.boost).

In both cases (S160 and S170), the control electronics of the motor at regular time units (for example, every second) calculates this additional power P.boost and sums it up to an additional power sum P.sum (step S180). Subsequently, in step S190, this additional power sum P.sum with a maximum additional power sum P.sum. max compared.

As soon as the additional power sum P.sum of the motor in boost mode the maximum additional power sum P.sum. exceeds max (YES in S190), the boost mode is terminated and the motor is operated in step S200 in the conventional "reduce mode" with a power limited to the nominal power P.max (P.incr = P.max) Power sum P.sum the maximum additional power sum P.sum max has not yet reached (NO in S190), the motor can basically continue to operate in boost mode.

Steps S110 to S200 are continuously repeated after the engine is turned on in the above-described manner until the engine is turned off. In order to prevent (pre-) damage to the electronic components, the motor is operated only to a limited extent in boost mode with an increased power P.incr. The first measure to adjust this limited scope is in the already described step S190, in which it is prevented that the additional power sum P.sum in boost mode a maximum additional power sum P.sum. exceeds max. The maximum additional benefit amount P.sum. max is preferably a fixed value, which depends on the respective motor.

As a second measure, it is checked in step S130 whether a boost mode is available at all. In particular, even if P.required has an increased power requirement, the system will not allow a boost mode (NO in S130) if it is assumed that an additional power sum P.sum from previous operating phases of the motor in boost mode is not yet complete or at least not yet sufficiently degraded (for example, by cooling).

In a first variant, in step S 30, the boost mode is provided only after the engine has been switched on for the first time. For this purpose, for example, when the motor is switched on in step S100, a flag can be set, which is reset only when the motor is switched off. This variant is based on the assumption that the engine has cooled down sufficiently again only after a certain switch-off time, so that it can easily be operated again in boost mode with increased power.

In a second variant, in step S130 the boost mode is only made available again when the motor has reduced the total additional power sum P.sum again. In the simplest case, a predefined power amount can be subtracted from the calculated additional power sum P.sum per unit of time. However, complex mathematical models are also conceivable which describe the thermal behavior of the engine.

In a third variant, the boost mode is only made available again in step S130 if the motor has reduced the additional power sum P.sum at least by a predetermined amount. Also in this case, a simple timing or complex mathematical models can be used. In a fourth variant, in step S130, the boost mode is only (again) available if there is currently a sufficient power buffer for the boost mode. For this purpose, a difference between the maximum additional power sum (P.sum.max) and the possibly at least partially reduced additional power sum (P.sum) of previous operations of the engine in boost mode is compared with a predetermined difference value and the boost Mode enabled only if this difference exceeds the predetermined difference value. In addition, various protection functions are also provided with this motor to prevent critical load cases such as overcurrent, overvoltage and excessive temperatures in the engine and electronics, as used for example in conventional systems. While in the embodiment described above, the operation of the engine is limited in performance, it is alternatively or additionally also possible to limit the operation of the engine in terms of time. For this purpose, for example, the boost mode is provided only for a predetermined period of time per boost mode and / or only for a predetermined total duration of all boost modes after the engine has been switched on.

FIG. 2 shows an exemplary time profile of the operation of an engine according to the method described above. The upper curve shows the actual power consumption P of the motor over time, and the lower graph shows the calculated additional power sum P.sum over time.

As long as the actual power requirement P.required is below the nominal power P.max of the motor, the power P of the motor corresponds to the current power demand P.required (phase 1). If the actual power requirement P.required exceeds the nominal power P.max of the motor in the course of the wash program, then the motor is operated with an increased power P = P.incr, but which is still below the absolute power limit P.limit (phase 2), if the boost mode is available. In this phase 2, an additional service P.boost is calculated and summed up to the additional power sum P.sum. If the power requirement P.required of the motor falls below the nominal power P.max again in a subsequent phase 3, then the motor is operated with the corresponding power P = P.required. At the same time the engine can cool down a bit, so that the additional power sum P.sum can reduce something again (falling lower curve). The subsequent phases 2 and 3 behave analogously.

For comparison, it should be noted that in conventional systems, the power range between the nominal power P.max and the absolute power limit P.limit is cut off, since the nominal power P.max represents a hard limit.

In addition, care is taken in the process that the calculated additional power sum P.sum below the predetermined maximum additional power sum P.sum. max stays.

LIST OF REFERENCE NUMBERS

P.boost extra power

P.incr increased performance

P.limit absolute power limit (which may not be exceeded)

P.max nominal power (which may not be permanently exceeded)

P.required current power requirement of the engine

P.sum additional sum of money

P.sum.max maximum additional benefit amount

Claims

A method of operating a motor of an electrical appliance, in particular a household electrical appliance, wherein the motor has an absolute power limit (P.limit) from which it can not be operated, without being damaged, and a nominal power (P.max), which is below the absolute performance limit (P.limit) and with which it can be operated permanently without being damaged,

characterized in that

In the case of an increased power requirement (P.required), which is above its nominal power (P.max), the motor is operated to a limited extent in an increased power (P.incr) boost mode which requires an additional power (P. P.boost) is above the nominal power (P.max), but does not exceed the absolute power limit (P.limit).

2. The method according to claim 1,

characterized in that

the operation of the motor is limited in power mode in boost mode.

3. The method according to claim 2,

characterized in that

the additional power (P.boost) is summed during operation of the motor in boost mode and the boost mode is terminated when the additional power sum (P.sum) exceeds a predetermined maximum additional power sum (P.sum.max).

4. The method according to any one of the preceding claims,

characterized in that

Operation of the engine in boost mode is limited in time.

5. Method according to one of the preceding claims,

characterized in that

the boost mode for the operation of the engine is only available if an additional power sum of previous operations of the engine in boost mode has been at least partially reduced again.

6. The method according to claim 5,

characterized in that

the boost mode for the operation of the engine is available again only after a predetermined period of time has elapsed since a last operation of the engine in boost mode.

7. The method according to claim 5 or 6,

characterized in that

the boost mode for the operation of the engine is only available if a difference between a predetermined maximum additional power sum (P.sum.max) and an optionally at least partially degraded additional power sum (P.sum) previous operations of the engine in the Boost mode exceeds a predetermined difference value.

8. The method according to claim 5,

characterized in that

the boost mode for the operation of the engine is only available once after the engine has been switched on.

9. Control device for operating a motor according to the method of one of claims 1 to 8.

10. Electrical device, in particular household electrical appliance, with a motor, which is operated according to the method according to one of claims 1 to 8.