US 4,227,128 A · Speed responsive motor control circuit

Abstract

A motor control circuit is provided for an appliance or the like of the type utilizing a speed adjustment device that controls an adjustable centrifugally controlled governor device. The governor includes a switch contact arrangement which is connected in the triggering circuit of a power switching device, a TRIAC for example, for selectively connecting the motor of the appliance to the power source connections. The switch contacts of the governor device open and close as the rotational speed of the motor increases and decreases respectively from the speed selected on the speed adjustment device. A variable impedance element mechanically coupled to and adjusted by the speed adjustment device is also provided in the triggering circuit of the power switching device in series with the governor switch contacts to vary the triggering of the power switching device as the speed setting is varied. Thus, a variable speed versus motor supply voltage characteristic is provided when the governor contacts are closed. A wider range of stable speed control is provided than is obtained with a governor device alone. Low speed cogging and high speed hunting problems are also minimized. The variable impedance element in various embodiments is arranged to provide a variable impedance characteristic over a portion of the speed adjustment device range and a fixed impedance over the remainder of the range.

Claims20

Dependent claims

A motor control circuit comprising:

mechanical speed sensing means coupled to the motor being controlled for sensing the speed of rotation and for selectively connecting and interrupting a first circuit path as the speed of the motor varies with respect to an adjustable predetermined speed;
power switching means having a control input and adapted to be connected in series with a power source connection and the motor to be controlled for selectively connecting the motor to the power source connections;
manually controlled speed adjustment means connected to said mechanical speed sensing means for selecting said adjustable predetermined speed;
and
phase control means having a first variable impedance element, said phase control means being responsive to said manually controlled speed adjustment means and connected to said control input of said power switching means, said manually controlled speed adjustment means adjusting the impedance of said first variable impedance element, said first circuit path provided by said mechanical speed sensing means being connected in series with said phase control means.

2 more elements

Dependencies are inferred from the claim text.

Speed responsive motor control circuit

Life of this patent

Speed responsive motor control circuit

Life of this patent

Abstract

Claims20