Vibration packet control

Working principle

Vibration
package control t_E: duty cycle
t_0: vibration package duration

The wave packet control or vibration packet control is used to control the power of electrical AC voltage consumers. Typical applications are electrical building heating or electronic instantaneous water heaters .

In contrast to phase control , the signal is only switched in the zero crossings. This largely avoids current and voltage transients and thus harmonics.

Implementations

Full wave control

Whole periods of the mains frequency are always switched on or off. This means that under no circumstances do constant components occur in the power consumption.

Half-wave control

Half-waves can also be switched to increase the continuity of the effective voltage. If direct current components are to be avoided, it must be ensured that negative and positive half-waves occur just as frequently.

(Classic) control with a fixed period

The period length P is constant (e.g. 64). Depending on the desired effective voltage, N periods (e.g. 20) of these are switched on and P − N periods (in this example 64 - 20 = 44) are switched off. Classic implementation using counter modules and digital comparators.

Control with variable period duration

The aim is control with a pulse train that hardly contains any low-frequency signal components. This is achieved through the use of delta-sigma modulators for control. This means that motors can be controlled without additional vibrations with 50 Hz / 60 Hz single-phase alternating voltage; with three-phase current, lighting systems can also be controlled without flicker.

Control by means of analog control circuits

Control is possible using integrators and comparators. The output signal is rectified and integrated. This voltage is compared with a reference voltage (which is adjustable). Depending on the deviation, the output signal is switched on or off.

Control by means of a microcontroller

The increasing availability of cheap microcontrollers enables control via software. Comfort functions can be implemented without additional material expenditure.

advantage

• with resistance heating almost no shift reactive power in the fundamental oscillation with electrical consumers.

disadvantage

• additional sub- and interharmonics distortion of the mains currents, therefore poor power factor although the active factor is very good.

restrictions

At 50 Hz / 60 Hz mains frequency, flicker may be perceived in the lighting . In the case of drives, vibration packet control results in a higher torque ripple, but this can be tolerated in some applications - such as the control of circulating pumps in solar thermal systems . With strongly integrating consumers such. For example, a radiant heater can control the power with any high resolution; with drives, the number of usable resolution steps is rather small due to the torque ripple that occurs (e.g. 25%, 33.3%, 50%, 66.7%, 75 % and 100%).

On the network side, d. H. Before the vibration packet control, the current gaps cause an increased distortion reactive power. The power factor only depends on the cycle ratio:

The line-side voltage results in the current and thus the apparent power as well as the real power . ${\displaystyle U=U_{\rm {N}}}$ ${\displaystyle {I={U_{\rm {N}} \over Z}\,{\sqrt {t_{\rm {E}} \over t_{0}}}}}$ ${\displaystyle {S={U_{\rm {N}}^{2} \over Z}\,{\sqrt {t_{\rm {E}} \over t_{0}}}}}$ ${\displaystyle {P={U_{\rm {N}}^{2} \over Z}\,{t_{\rm {E}} \over t_{0}}}}$

${\displaystyle PF={\sqrt {t_{\rm {E}} \over t_{0}}}}$

When using several vibration packet controls, the poor power factor can be compensated for by controlling the individual controls in such a way that the network current has the highest possible overall duty cycle.

Mode of action

The vibration package control switches vibration packages. A vibration package consists of a number of complete sinusoidal vibrations. The control switches on exactly at the zero crossing of the voltage and also switches off again at the zero crossing. The ratio of the switch-on time to the oscillation packet duration results in the desired effect of reduced power consumption by the downstream consumer. ${\displaystyle T_{\rm {e}}}$ ${\displaystyle T_{\rm {0}}}$ ${\displaystyle P_{\rm {red}}}$

Calculation of the effective power depending on the duty cycle:

${\displaystyle P=P_{\rm {N}}\,{t_{\rm {E}} \over t_{0}}}$

Calculation of the effective voltage depending on the duty cycle:

${\displaystyle U=U_{\rm {N}}\,{\sqrt {t_{\rm {E}} \over t_{0}}}}$

Individual evidence

1. ↑ Press release from the pump manufacturer Grundfos online  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. and description of a solar system control from Resol online ( memento of the original from July 20, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 5.7 MB) (both accessed on May 10, 2010).