The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 08, 2005
Filed:
Jul. 09, 2002
James W. Ratz, Bloomington, MN (US);
Paul E. Sigafus, Medina, MN (US);
Larry L. Lutton, Burnsville, MN (US);
Nickolas G. Vrionis, Los Altos, CA (US);
James W. Ratz, Bloomington, MN (US);
Paul E. Sigafus, Medina, MN (US);
Larry L. Lutton, Burnsville, MN (US);
Nickolas G. Vrionis, Los Altos, CA (US);
Varidigm Corporation, Plymouth, MN (US);
Abstract
An HVAC system has at least one variable speed controller for an AC induction motor, especially of the Permanent Split Capacitor (PSC) type. The variable speed controller provides switched power via a modulating triac to the main coils of the motor and constant power via an on/off triac to the auxiliary coils during operation. A large value capacitor is placed in line with the auxiliary coils to reduce power consumption and current draw over that of known systems. Power to the motor can be turned off to provide for motor speed sensing through monitoring the frequency of a generated voltage when the power is turned off. Frequency-based motor speed sensing is accomplished by shutting off all current to the motor and measuring zero crossings on the generated voltage of the decaying magnetic field. The controller can be easily retrofitted onto existing motors. An optional controller bypass is provided to run the motor at rated speed in case of controller failure.