US 4,394,606 AGranted

Speed control circuit for electric motor

AssigneeDupro AG

InventorPeter Woerwag

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Abstract

Disclosed is an apparatus for controlling the rotational speed of an electric motor based upon the load encountered by the electric motor. A load sensor provides a voltage level based upon the operating load of the electric motor and accumulates this voltage in accordance with the cycle of the alternating current supplied to the motor. If during a cycle of the alternating current, the voltage exceeds a predetermined level, a transistor will be biassed into conduction, said transistor turning off a thyristor and preventing any further conduction of the thyristor during that cycle of the alternating current. Thus the duty cycle of the thyristor determines the total amount of current supplied to the electric motor and this current level determines the rotational rpm of the motor.

Claims10

Dependent claims

An apparatus for cleaning textile floor coverings, said apparatus including a roller shaped brush, an electric motor for rotating said roller shaped brush, and a suction device for evacuating dirt and dust particles from said floor covering, said motor connected to an alternating current supply and having a load current passing therethrough and an adjustable rotational speed, a circuit arranged in the load circuit of the motor to control the rpm of the motor as a function of its load current, comprising:

(a) a measuring resistance connected in said load circuit for producing a measuring signal proportional to said load current;
(b) a thyristor having an anode and a cathode and being connected in at least one branch of said load circuit:
(c) a control circuit connected to actuate said thyristor, said control circuit comprising a series circuit arranged in parallel to the anode and cathode of said thyristor, said series circuit including a coupling resistor and a switching transistor having an emitter and a collector, said coupling resistor being connected to the collector of said switching transistor;
(d) said thyristor having a control electrode connected through a diode to the collector of said switching transistor, said switching transistor having a base electrode connected through a resistance to a parallel circuit comprising a capacitor and a variable resistor, and a diode connecting said measuring signal from said measuring resistance to said resistance in series with said switching transistor base electrode.

1 more element

In a device for cleaning textile floor coverings, said device having a roll shaped brush driven by an alternating current motor for the treatment of the floor covering, a suction device for drawing dirt and dust particles from the floor covering, a circuit for controlling the rpm of said electric motor, said circuit comprising:

a semi-conductor device connected between said motor and said alternating current power supply, said semi-conductor device being actuatable for electrically connecting said alternating current power supply to said motor, and deactuatable;
means for sensing current passing through said motor and providing a signal proportional thereto;
and
actuation means connected to said semi-conductor device for actuating said semi-conductor device at a variable point during each cycle of current from said AC supply, said semi-conductor device being deactuated upon each zero crossing of said current from said AC supply, said actuation means being connected to receive said signal from said sensing means and being connected to said alternating current supply, and further including timing means for reducing the period of actuation of said semi-conductor device in response to an increase in said current passing through said motor, whereby as the current passing through said motor increases, the rpm of said motor is decreased.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 06/209,154Filed 21 Nov 1980
Priority: DE 294693021 Nov 1979
Granted: 19 Jul 1983
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

A47L 9/2889
Installation of the electric equipment, e.g. adaptation or attachment to the suction cleaner; Controlling suction cleaners by electric means:…
A47L 9/2847
Characterised by the parts which are controlled: surface treating elements
A47L 9/2857
Installation of the electric equipment, e.g. adaptation or attachment to the suction cleaner; Controlling suction cleaners by electric means: user…
H02P 25/04
Characterised by the kind of motor: single phase motors, e.g. capacitor motors

Family

No related US applications are recorded in the indexed filing history.

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