Electricity: motive power systems – Alternating current commutating motors – Universal or a.c.-d.c. motors
Patent
1993-06-24
1996-06-25
Shoop, Jr., William M.
Electricity: motive power systems
Alternating current commutating motors
Universal or a.c.-d.c. motors
H02P 532
Patent
active
055303250
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention is based on a control circuit with phase shift control for a universal motor.
BACKGROUND
A control circuit of Telefunken is already known, which is designed as an integrated circuit and is identified by U2008B. This integrated circuit is supplied by the rectified d.c. current supply. The ground connector is directly connected with the second net connector. If a potential separation between the load current circuit and control current circuit of the triac is required, a transformer element such as an optical coupler or an ignition transformer is required. Not only is this additional element relatively expensive, but it also represents an additional failure risk.
SUMMARY OF THE INVENTION
In contrast thereto, the control circuit of the invention has the advantage that expenses are saved because of the omission of the transformer element. In addition, the strip conductor track on the printed circuit board is simplified in an advantageous manner.
A particularly advantageous disposition for the control pick-up 31 is obtained because it is possible to do without potential-separating means.
It is also advantageous that the motor winding can be used as a measuring resistor, and a resistor can thereby be dispensed with.
It is particularly advantageous when an auxiliary source is connected between the ground connector and the synchronizing connector in the control circuit, which contributes to maintain the synchronizing voltage in case of small operating angles. A particularly simple solution for the auxiliary source results when it contains a storage-capacitor which can be charged by the line voltage. Capacitors of this type require little space and can be obtained at small cost.
Because the control circuit can be put together with only a few components and therefore requires only little space, it is particularly suitable for use in electrical hand tools.
DRAWINGS
An exemplary embodiment of the invention is illustrated in the drawings and will be described in detail in the following description.
FIG. 1 shows a known circuit diagram and
FIG. 2 shows a circuit diagram of the exemplary embodiment.
FIG. 3 shows a hand tool incorporating the universal motor and control circuitry of the exemplary embodiment.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
It is known to employ the control circuit U2008B (Telefunken) of FIG. 1 for rpm control of an electric motor M connected to an a.c. voltage supply, with the load circuit of which a TRIAC (registered trademark for a gate-controlled semiconductor switch) is connected. In this case the control circuit is supplied via an input terminal VSS by means of a rectified voltage of the line supply, and a ground connector GND is connected with a second line of the line supply. It must be stressed in connection with this known circuit that it is necessary that the ground connector GND and the triac cathode be connected in series with the measuring resistor directly with the second connector of the line supply and an input Usyn via a resistor Rsyn with the first connector of the line supply.
In the circuit arrangement of FIG. 2, a control circuit 2 and a semiconductor switch in the form of a TRIAC 3 are inversely connected with the known circuit arrangement of FIG. 1. An electric motor 1 with its magnetic windings 11, 12 is connected in series with the triac 3 via a measuring resistor 10 at supply line terminals 13, 14 in a load current circuit. On the cathode side, the triac 3 is connected with the measuring resistor 10 at a junction 25. Furthermore, a ground connector 20 of the control circuit 2 is connected at the junction or internal ground point 25. The voltage supply of the control circuit 2 takes place via an input 23 from the voltage of the supply line rectified by means of diodes 17, 18. The rectified voltage is supplied via a series resistor 16 to the input 23 of the control circuit 2 as well as to the input E of a controller or RPM sensor 4.
The voltage is smoothed by means of a filter capacitor 15 which is connected to the ground co
REFERENCES:
patent: 4540318 (1985-09-01), Hornung et al.
patent: 4618805 (1986-10-01), Hornung
Willy Frank, "Phasenanschnittsteuerungen--problembezogen," in journal Elektronik, vol. 34, No. 4, pp. 86-90, Feb. 1985.
D. Dahms, "Familie integrierter Schaltungen zur Phasenanschnitt steuerung bzw. Null spannungs schaltung," in journal Radio Fernsehen Elektronik, vol. 37, No. 9, pp. 564-567, published 1988, East Berlin, Germany.
Friedrich Hornung
Matthias Heisler
Robert & Bosch GmbH
Shoop Jr. William M.
Sircus Brian
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