Electricity: motive power systems – Induction motor systems – Reversing
Patent
1990-05-22
1991-12-24
Shoop, Jr., William M.
Electricity: motive power systems
Induction motor systems
Reversing
318756, 318777, 318775, 318749, H02P 320, H02P 906
Patent
active
050756117
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a control device for an alternating-current motor operating in single-phase and having at least a first and a second winding, one coupled with the other such that they are shifted in phase with respect to each other, comprising a line connection, a first and a second winding connection for the first and the second winding, respectively, of the alternating-current motor, a control unit including a first and a second switching element located between the line connection and the first and the second winding connection, respectively, one of the switching elements being open in a switching state of the control unit, depending on the running direction of the alternating-current motor, and the other being closed, and at least one of the switching elements being open in a state of rest of the control unit, and a power supply unit for making electric energy available for the control unit.
In the control devices known so far, it has always been necessary for the power supply unit to have both the phase and the neutral conductor leading to the control device in order that the power supply unit is capable of constantly supplying the control unit with the necessary electric energy. If such a control device is to replace an electromechanical switch which is already available and which only switches, for example, the phase onto one of the winding connections of the electric motor, there is the problem that in addition to the line for the phase and the lines for the two winding connections, the neutral conductor has to be linked up in order to ensure that this control device is constantly supplied with power independently of operation of the alternating-current motor. Problems arise particularly when this is to be carried out within the scope of a home installation, more particularly, using an available socket installed when the building was constructed.
SUMMARY OF THE INVENTION
The object underlying the invention is, therefore, to so improve a control device of the generic kind that operation thereof is possible without linking up an additional neutral conductor to the control device.
This object is accomplished in accordance with the invention with a control device of the kind described at the beginning in that the power supply unit operates in the state of rest of the control unit by drawing on a first potential difference between the line connection and a winding connection associated with the switching element open in the state of rest and in the switching state of the control unit by drawing on a second potential difference between the line connection and the winding connection associated with the switching element open in the switching state.
Hence the gist of the invention is to be seen in that in the state of rest, the full voltage present at one of the switching elements is drawn on for operation of the power supply unit, with the control device getting the minimal electric energy required for operating it, on the one hand, via the line connection and, on the other hand, via the alternating-current motor from the neutral conductor. In the switching state of the control unit, on the other hand, the voltage drop between the first and the second winding connections is drawn on, this corresponding to the phase shift between the two windings for generation of a rotating field required for running of the motor. Since, in the switching state, the control unit connects a winding connection with the line connection, the voltage between the line connection and the winding connection associated with the open switching element is, consequently, drawn on. As the shift in phase between the two windings is brought about by, for example, a motor capacitor, the voltage applied in this case to the power supply unit corresponds to the voltage drop across this motor capacitor during operation of the alternating-current motor.
Since the control devices according to the invention serve, for example, to control alternating-current motors used to operate roller-type shutters, sun
REFERENCES:
patent: 3619747 (1971-11-01), Pedersen
patent: 3896355 (1975-07-01), Guicheteau
patent: 4087728 (1978-05-01), Porter
patent: 4413211 (1983-11-01), Fowler
patent: 4451775 (1984-05-01), Phillips et al.
patent: 4649330 (1987-03-01), Kim
Cabeca John W.
Lipsitz Barry R.
Shoop Jr. William M.
Torotron Elektronik GmbH
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