Drive control with overload protection for a drill device
First Claim
1. A drive control for a drilling device with a series wound universal motor, comprising means for effecting current limitation to said motor when a load limit moment (M limit) is reached, wherein the improvement comprises:
- a circuit containing said motor (1), said circuit is connected to a supply voltage;
an rpm regulator (4) located in the circuit for comparing an actual rpm value (N act) of said motor with a constant reference rpm value (N ref), said regulator (4) having an output voltage;
means in said circuit and responsive to said regulator output voltage for maintaining the actual rpm value corresponding to the constant reference rpm value;
said means for maintaining comprises a first decoupler diode (5) and a second decoupler diode (10), said first and second decoupler diodes (5,
10) having a junction point, wherein said rpm regulator (4) reaches maximum output voltage at a fraction point (Mn) of the load limit moment (M limit), and wherein the voltage at the junction point of said decoupler diodes remains constant during an increase in torque from the fraction point (Mn) to the load limit moment (M limit); and
a current regulator (9) in said circuit for reducing the voltage at said junction point only when the load limit moment (M limit) is reached.
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Abstract
Drive control for a drilling device including a universal motor is arranged so that the total available mains voltage is applied when a fraction of the motor torque, available for the full work range of the device, is reached. If a higher torque is desired, the motor torque/rotational speed curve follows the natural characteristic line until a load point is reached where current limitation occurs. Accordingly, as the motor speed decreases as the normal work range is exceeded, the operator of the drilling device is signaled concerning the load state due to the noise developed in the drilling device.
43 Citations
2 Claims
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1. A drive control for a drilling device with a series wound universal motor, comprising means for effecting current limitation to said motor when a load limit moment (M limit) is reached, wherein the improvement comprises:
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a circuit containing said motor (1), said circuit is connected to a supply voltage; an rpm regulator (4) located in the circuit for comparing an actual rpm value (N act) of said motor with a constant reference rpm value (N ref), said regulator (4) having an output voltage; means in said circuit and responsive to said regulator output voltage for maintaining the actual rpm value corresponding to the constant reference rpm value; said means for maintaining comprises a first decoupler diode (5) and a second decoupler diode (10), said first and second decoupler diodes (5,
10) having a junction point, wherein said rpm regulator (4) reaches maximum output voltage at a fraction point (Mn) of the load limit moment (M limit), and wherein the voltage at the junction point of said decoupler diodes remains constant during an increase in torque from the fraction point (Mn) to the load limit moment (M limit); anda current regulator (9) in said circuit for reducing the voltage at said junction point only when the load limit moment (M limit) is reached.
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2. A drive control for drilling device with a series wound universal motor and current limitation when a load limit moment (M limit) is reached, wherein the improvement including that a motor torque/rotational speed characteristic line is selected for said drive control so that the total available supply torque is at a fraction (Mn) of the motor torque available for the total work range of the motor, comprises:
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a first line connected to said universal motor for supplying mains voltage therethrough;
a triac located in said first line;a second line connected to said universal motor;
a tachogenerator located in said second line for measuring an actual rpm of said motor;a third line connected between said first line and said second line, said third line is connected to said first line via said triac; an rpm regulator located in said third line; a constant reference value source connected to said rpm regulator for providing a reference rpm value;
a pulse control stage in said third line having an input connected to an output of said rpm regulator via a first decoupler diode, and having an output connected to said triac for controlling the triac so that the actual rpm value of said motor corresponds to the reference rpm value;
a sensor resistance in said first line for measuring the current flowing through said motor;
a current reference value generator located in said second line and having an input and an output;
a rectifier in said second line and connected to the output of said current reference value generator, said rectifier is arranged to rectify the current measured by said sensor resistance; anda fourth line connects said second line between said current reference value generator and said rectifier, and connects said third line between said first decoupler diode and said pulse control stage;
a current regulator located in said fourth line; and
a second decoupler diode located in said fourth line between said current regulator and said third line, whereby said first and said second decoupler diodes take care, respectively, of a smaller modulation value of said rpm regulator and said current regulator.
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Specification