Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1993-02-02
1994-10-25
Ro, Bentsu
Electricity: motive power systems
Induction motor systems
Primary circuit control
318795, 318805, H02P 7622
Patent
active
053592735
DESCRIPTION:
BRIEF SUMMARY
The invention relates to load-control circuit for a mains-operated single-phase asynchronous capacitor motor corresponding to the preamble of claim 1. The invention relates further to the use of such a circuit in a postage metering machine.
Asynchronous capacitor motors, which are operated at the general single-phase mains (for example 220 V, 50 Hz) are known in general and widespread. They are economical, sturdy, and operate without service requirements. In addition to their positive properties, however, they are also associated with disadvantages. The asynchronous capacitor motors have a poor efficiency, which is in general below 50%. Thereby a relatively large power dissipation is always generated, where the power dissipation can heat the motor windings up to critical temperatures of above 100.degree. C. This substantial power dissipation is also present during idling of the motor.
It is further known that asynchronous capacitor motors furnish only a relatively small starting torque during the starting from a standstill. For improving of this property an additional capacitor can be connected to the motor capacitor for starting.
A postage metering machine is known from Hasler Review, Vol. 11, 1978, No.1, pages 2-7, which postage metering machine includes an asynchronous capacitor motor as a drive. This motor runs in the substantially idling state after the switching on of the machine, wherein the motor drives the pull-in rollers for the letters to be metered. As soon as the letter is to be metered, the print rotor of the machine is coupled to the motor and accelerated through a coupler. The mechanical load of the capacitor motor increases substantially for a short time during this procedure.
The mode of operation of the capacitor motor is thus such that the capacitor motor is loaded predominantly only very little in order to be loaded substantially more over a short time period. The strength of the load depends in this case also on the kind of the letters which have to be metered, in particular on the thickness of these letters, where the thickness can vary between less than 1 mm and about 8 mm.
The construction of the capacitor motor in this case is directed to the load peaks whereby, in case of a weak load, there result relatively unfavorable operating conditions and where, based on the unfavorable operating conditions, the complete postage metering machine is subjected to a substantial thermal load.
It is an object of the invention to furnish a general drive motor for a postage metering machine with its specific kind of motor load, where the drive motor generates substantially less heat than up to now while maintaining the general costs at the same level.
The solution of this object is furnished by the characterizing part of the independent claims. The dependent claims provide specific embodiments of the invention.
The invention is described in the following in more detail by way of the examples in two figures. There is shown in:
FIG. 1-- schematic diagram of a load-control circuit.
FIG. 2-- detailed switching diagram of the load-control circuit.
FIG. 1 shows the schematic diagram of a load-control circuit for a mains-operated single-phase asynchronous capacitor motor 11. This motor 11 is constructed for example with four poles. The main windings of the motor are connected through the connections 13, 14 as well as 15 to a single-phase alternating-current mains of the standard 220 V, 50 Hzb, or 110 V, 60 Hz, for example through a mains plug 18. A first capacitor 19 is connected to a shunt winding of the motor 11, and this shunt winding is connected to the connection 15 with alternating current through which capacitor 19.
The arrangement described so far corresponds to a generally known capacitor motor, wherein the windings of the motor 11 and the capacity value of the first capacitor 19 are tuned in such a way to each other that optimum situations result in connection with the substantially unloaded running of the motor 11, i.e. in particular a lowest possible power dissipation.
There is now provided a
REFERENCES:
patent: 4675565 (1987-06-01), Lewus
patent: 4703387 (1987-10-01), Miller
patent: 4806838 (1989-02-01), Weber
patent: 4885655 (1989-12-01), Springer et al.
Publication: "Hasler Mailmaster F 204-Franking Machine" Hasler Review, vol. 11, No. 1.
Ascom Hasler Mailing Systems AG
Kasper Horst M.
Ro Bentsu
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