DE102006006960B4 - Procedure and electrical device - Google Patents

Abstract

A method for operating an electrical device that is a converter, an inverter, a regenerative device or another device comprising power semiconductor switches, the electrical device comprising power electronics operated with pulse width modulation, depending on the temperature, in particular temperature of the power components, power semiconductors or heat sinks, a constant PWM frequency or a mixed-clocked PWM frequency is used, with the mixed clocking: a first PWM frequency being used in a first time period and a second PWM frequency being used in a second time period, which differs from the first, the time periods being integer multiples a basic period, the time spans following one another in a repeating sequence, the time spans being smaller than a thermal time constant of a layer or component of a power semiconductor switch of the power electronics, the basic period being a timer of the software Device is assigned, characterized in that - below a first temperature value a first PWM frequency is used - above a second temperature value a second PWM frequency is used - a mixed clock is used between the first and second temperature value.

Description

The invention relates to a method and an electrical device

From the DE 102 48 375 C2 a method for current detection in converters is known. The current values recorded in the rhythm of the pulse width modulation frequency, i.e. PWM frequency, are used to control the speed and / or the torque of the electric motor supplied by the converter.

From the 5 to 9 It is clear that a current value can be recorded per PWM period. In some applications it is also sufficient to record only one current value per every second, third or fourth PWM period.

With some inverters, the duration of the PWM period can only be implemented as an integer multiple of a basic period. For example, depending on the software or hardware, a timer is set with this basic period, to which the entire software and the current measurement are aligned.

From the U.S. 5,068,777 A For example, the closest prior art is a pulse-width-modulated inverter which has temperature compensation.

The invention is therefore based on the object of achieving lower and / or more pleasant noise emissions in electrical devices.

According to the invention, the object is achieved in the method according to the features specified in claim 1 or 3 and in the electrical device according to the features specified in claim 5.

Important features of the invention in the method are that it is intended to operate an electrical device, this comprising power electronics operated with pulse width modulation,
wherein a first PWM frequency is used in a first period of time and a second PWM frequency that differs from the first is used in a second period of time.

The advantage here is that the noise emission is lower and more pleasant than when using only one frequency. The time periods can be dimensioned in such a way that the switching losses of the power semiconductor switches nevertheless remain low.

In an advantageous embodiment, further PWM frequencies are used in further time periods. The advantage here is that the noise emission is even more pleasant.

In an advantageous embodiment, the time periods follow one another in a repeating sequence. The advantage here is that natural vibrations of components can only build up within the time periods. By alternating quickly, only low amplitudes are achieved for the natural oscillations or oscillations of device components.

In an advantageous embodiment, the time periods are shorter than a thermal time constant of a layer or component of a power semiconductor switch of the power electronics. The advantage here is that the temperature changes only slightly when changing the PWM frequencies. Thus, the change in the mechanical stresses between subregions of the power semiconductor, such as semiconductor layers, bonds, housings and the like, relative to one another is small and thus the service life of the device is long.

In an advantageous embodiment, the time periods are integer multiples of a basic period. The advantage here is that the control software can be executed simply and quickly in accordance with the invention.

In an advantageous embodiment, the basic period is assigned to a timer in the software of the device. The advantage here is that devices whose operating and / or control and / or regulating software is constructed in such a way that a timer is provided, with values being determined in the rhythm specified by this, such as current measured values or the like. However, the basic period can only be changed with great effort.

In an advantageous embodiment, the device is a converter, an inverter, a feedback device or another device comprising power semiconductor switches. The advantage here is that the invention can be applied to different types of devices if these comprise semiconductor switches controlled in a pulse-width-modulated manner, the PWM frequency being constant in this type of device in the prior art. By means of the invention, two or more frequencies are then used in an alternating sequence, the frequency remaining constant in the respective individual time interval.

Important features of the electrical device are that it comprises power electronics that can be operated with pulse width modulation, the device being designed in such a way that it can be operated with different PWM frequencies, in particular in such a rapid sequence, i.e. mixed clocking, that the mixed clock period is shorter than a thermal time constant . The advantage here is that the effects of the mechanical stresses or whose changes can be reduced. In particular, the alternating load operation can be reduced and the service life can thus be increased.

Essential features of the further method for operating an electrical device are that it includes power electronics operated with pulse width modulation,
depending on the temperature, in particular the temperature of the power components, power semiconductors or heat sinks, a constant PWM frequency or a mixed-clocked PWM frequency is used.

Advantageously, the optimal method can therefore always be carried out in order to minimize the switching losses on the one hand and the noise on the other hand.

• - unterhalb eines ersten Temperaturwert eine erste PWM-Frequenz verwendet
• - oberhalb eines zweiten Temperaturwert eine zweite PWM-Frequenz verwendet
• - zwischen erstem und zweitem Temperaturwert eine Mischtaktung verwendet.

Von Vorteil ist dabei, dass nicht nur die Mischtaktung, sondern auch konstante Frequenzen anwendbar sind.In an advantageous embodiment

• a first PWM frequency is used below a first temperature value
• - a second PWM frequency is used above a second temperature value
• - a mixed cycle is used between the first and second temperature value.

The advantage here is that not only the mixed clock, but also constant frequencies can be used.

In an advantageous embodiment, mixed clocking is produced from the first and second PWM frequencies. In particular, the first PWM frequency is used for a first individual time span and the second PWM frequency is used for a second individual time span, first and second individual time spans always following one another alternately. The advantage here is that the cycle ratio can be changed as a function of the temperature.

In an advantageous embodiment, the period of the mixed clocking is greater than the PWM period of the first PWM frequency, in particular equal to or greater than twice the first PWM frequency. In an advantageous embodiment, the mixed clock is composed of more than two PWM frequencies. The advantage here is that a very pleasant, quiet generation of noise can be achieved.

Further advantages result from the subclaims.

• In der 1 ist ein erfindungsgemäßes Verfahren schematisch gezeichnet. Dabei ist eine Mischtaktung im Verhältnis 3 zu 4 gezeigt. In einem ersten Zeitintervall, nämlich dem längeren, ist dabei eine PWM-Frequenz von 16 kHz und in einem zweiten Zeitintervall, nämlich dem kürzeren, ist eine PWM-Frequenz von 8 kHz vorgesehen.

The invention will now be explained in more detail with reference to figures:

• In the 1 a method according to the invention is shown schematically. A mixed cycle in a ratio of 3 to 4 is shown. In a first time interval, namely the longer one, a PWM frequency of 16 kHz is provided and in a second time interval, namely the shorter one, a PWM frequency of 8 kHz is provided.

Each of the two time intervals is an integer multiple of the basic period, which is 250 microseconds, for example.

In the 2 a different ratio is shown, with 8kHz and 16kHz each being selected.

With these mixed clocks, low-noise operation can be achieved with nevertheless low power loss of the power semiconductor switches of the device, such as converters, inverters, feedback units or the like.

The switching losses of the power semiconductor switches are lowest at low frequencies, but at these frequencies the noises are most annoying and unpleasant for the human ear. Also, noise generated when using a constant PWM frequency is unpleasant and annoying.

The mixed operation makes the noise more pleasant and natural vibrations of the components of the device are less strongly stimulated.

The individual time periods are preferred t _8kHz and t _16kHz shorter than the thermal time constant of the power semiconductor. In this way, alternating load operation can be avoided and the service life of the power semiconductors can be extended. This is because thermal changes in mechanical stress caused by temperature fluctuations have a negative effect on the service life. In order to keep the temperature swings small, the individual time periods should be smaller than the thermal time constant of a layer or component of the power semiconductor switch or of the chip housing of the power semiconductor switch.

In a further embodiment according to the invention, the mixing cycle described is changed as a function of temperature. This means that the individual time intervals are made dependent on the temperature corresponding to the power semiconductor switch. The alternating load operation is prevented by the mixed cycle. The relative ratio of the individual time intervals to one another is therefore determined as a function of the temperature. Thus, with increasing temperature, usually caused by increasing load, the individual time interval corresponding to the lower frequency is lengthened compared to the other individual time interval.

In a further embodiment according to the invention, a constant high frequency, for example 16 kHz, is applied at a low temperature, which corresponds to a very low load. Only when the temperature rises, for example when the load increases, the above-described mixed cycle is activated. If the workload is very high, a constant low frequency, for example 4 kHz, is then applied.

In this method, at least three different operating modes are coupled, which are selected depending on the temperature. Thus, low switching losses and pleasantly quiet noises can be achieved during operation.

List of reference symbols

t16kHz

Single time span

t _8kHz

Single time span

Claims (5)

A method for operating an electrical device that is a converter, an inverter, a regenerative device or another device comprising power semiconductor switches, the electrical device comprising power electronics operated with pulse width modulation, depending on the temperature, in particular the temperature of the power components, power semiconductors or heat sinks, a constant PWM frequency or a mixed-clocked PWM frequency is used, with the mixed clocking: a first PWM frequency is used in a first time period and a second PWM frequency is used in a second time period, which differs from the first, the time periods being integral multiples are a basic period, the time periods following one another in a repeating sequence, the time periods being smaller than a thermal time constant of a layer or component of a power semiconductor switch of power electronics, the basic period being a timer of Sof tware of the device is assigned, characterized in that - below a first temperature value a first PWM frequency is used - above a second temperature value a second PWM frequency is used - a mixed clock is used between the first and second temperature value. Procedure according to Claim 1 , characterized in that further PWM frequencies are used in further time periods. Procedure for operating an electrical device, wherein the electrical device comprises power electronics operated with pulse width modulation, depending on the temperature, in particular the temperature of the power components, power semiconductors or heat sinks, a constant PWM frequency or a mixed-clocked PWM frequency is used, with - A first PWM frequency is used below a first temperature value - A second PWM frequency is used above a second temperature value - a mixed clock is used between the first and second temperature value, the mixed clock being produced from the first and second PWM frequency, the first PWM frequency being used for a first individual time span and the second PWM frequency being used for a second individual time span first and second individual time spans periodically always alternating, the period of the mixed clocking being greater than the PWM period of the first PWM frequency, in particular equal to or greater than twice the first PWM frequency. Method according to at least one of the preceding claims, characterized in that the mixed clock is composed of more than two PWM frequencies. Electrical device, in particular for carrying out a method according to one of the preceding claims, comprising power electronics that can be operated with pulse width modulation, characterized in that the device is designed in such a way that it can be operated with different PWM frequencies in such a rapid sequence, i.e. mixed clocking, that the mixed clock period is shorter is a thermal time constant of the power semiconductor.

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