Electricity: power supply or regulation systems – Output level responsive – Phase controlled switching using electronic tube or a three...
Patent
1998-05-18
1999-11-16
Tso, Edward H.
Electricity: power supply or regulation systems
Output level responsive
Phase controlled switching using electronic tube or a three...
323322, 315291, G05F 110, G05F 100, G05B 2402
Patent
active
059864400
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for controlling the power supplied to a load fed from a source of ac voltage U of period T via a generalized phase adjustment system.
BACKGROUND OF THE INVENTION
To satisfy the standards relating to the limit of disturbances in the network by electrical apparatus which are of the resistive or inductive type or a combination of these two types, the applicant has previously described a first control process which is the object of French patent application filed under No. 94 12833.
In such a process, for a previously set nominal value, there is delivered successively to said load, periodically a sequence of a whole number p of elements, p being greater than one, each element, of number i, of the sequence being characterized by the whole number n.sub.i of periods T during which the ac voltage U is symmetrically chopped at a phase angle .alpha..sub.i corresponding to a duration t.sub.i during which the load is not supplied, the consecutive phase angles .alpha..sub.i of the element i and .alpha..sub.i+1 of the element i+1 being different and the combination of the angles .alpha..sub.i . . . .alpha..sub.i . . . .alpha..sub.p being selected such that it satisfies the standards.
This first control process could give rise in certain cases of use and particularly in electrical motors, of mechanical vibrations due to the cycle of modulation of the phase angles.
SUMMARY OF THE INVENTION
The present invention seeks to avoid particularly this drawback and has for its object a simple and effective control process for the power supplied to a load no matter what the resistive type such as a heating resistance, or no matter what the inductive type such as an electric motor.
According to the invention, for a preliminarily fixed nominal power, there is delivered successively to said load, periodically a sequence of a whole number p of elements, p being greater than one, each element, of number i, of the sequence being characterized by the whole number n.sub.i of half-periods T/2 during which the ac voltage U is chopped according to different consecutive phase angles .alpha..sub.i from .alpha..sub.1 to .alpha..sub.n corresponding respectively to durations t.sub.i from t.sub.1 to t.sub.n during which the load is not supplied, the phase angles .alpha..sub.i of the element i and .alpha..sub.i+1 of the element i+1 being similar repetitive values such that the mean current will be zero over a complete cycle whilst supplying the desired power to the load.
Thanks to this new process, the standards are satisfied no matter what the loads, as to the limitation of disturbances created in the network by the electrical apparatus, particularly the standards EN60555-2, CEI555-2, as well as their successors EN61000-3-2 and CEI1000-3-2, limiting the level of harmonic currents, and the standards EN60555-3, CEI555-3, as well as their successors EN61000-3-3 and CEI1000-3-3, limiting the relative variations of the voltage as a function of the number and these variations per unit of time for an impedance source defined by the standard and which are the cause of known disturbances called "FLICKER".
According to another important characteristic of the invention, the whole number n.sub.i of half-periods T/2 is uneven.
Thus, in the particular use in motors, there is a considerable improvement in the problems of mechanical vibrations particularly by creating higher frequencies of vibrations not less than multiples of 50 Hz.
BRIEF DESCRIPTION OF THE DRAWINGS
The characteristics and advantages of the invention will become apparent from the description which follows, by way of non-limiting example, with reference to the accompanying drawing, in which:
FIG. 1 is a chronogram of the instantaneous voltage as a function of time, for a power control according to the invention;
FIG. 2 is a synoptic diagram of a power control device according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
In the description which follows, the invention is described more particularly applied to
REFERENCES:
patent: 4980836 (1990-12-01), Carter et al.
patent: 5796245 (1998-08-01), Beaulieu et al.
D. Berghanel, "Schwingungspaketsteuerung zur Leistungsregulierung elektrischer Maschinen", pp. 389-391, Radio Fernsehen Elektronik, vol. 33, No. 6, Jun. 6, 1984.
Deschenes Laurent
Guinet Michel
Moulinex (S.A.)
Patel Rajahkant B.
Tso Edward H.
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