SHAFT POSITION SYNCHRONIZATION MEANS
FOR MULTIPLE SYNCHRONOUS INDUCTION
The synchronization of several rotating mechanical devices at the same speed, or rotational velocity, is commonly accomplished through the use of synchronous alternating current (a.c.) motors. Through the use of a.c. motors which are speed synchronous relative to the a.c. power frequency, no direct mechanical connection, other than electrical wiring, need exist between the individual mechanical devices. Therefore, the motor driven devices may be located separately and yet act as though they are physically linked together.
The instant invention improves on this speed, or rotational velocity synchronization through additionally providing exact angular position synchronization be- 20 tween the key rotating member of each a.c. motor. The synchronization is provided through the designation of one motor as the MASTER, while each additional motor which must be angularly synchronized with the .MASTER is provided as a SLAVE. In each case, the 25 motor may be a different size or kind of a.c. synchronous motor and of ordinary design.
The MASTER and each SLAVE are fitted with shaft angle position sensors which provide an electric signal usually denotative of the shafts desired lock-in, or 30 "zero" index position. The MASTER signal is brought together with each SLAVE signal in an electrical combining circuit which produces at least an ERROR signal when the respective SLAVE is not angularly synchronized with the controlling MASTER. This ERROR 35 signal acts to disrupt the speed of the SLAVE motor, allowing angular shaft position slippage relative to the instant shaft position of the MASTER until angular synchronization is achieved. When angular synchronization, or lock-in occurs, the ERROR signal ceases and 40 the SLAVE motor rotates synchronously with the MASTER motor, keeping an exact angular shaft position relationship therebetween.
It is therefore a purpose of the invention to provide exact angular, as well as rotational velocity synchroni- 45 zation between two or more electric motor machines.
A further purpose of the invention is to teach a method whereby a SLAVE motor may be brought into exact angular, as well as rotational velocity synchronization with a MASTER motor rotating member. 50
Yet another intent of the invention shows means for controllably retarding the normal angular rotational velocity of a SLAVE motor shaft member relative to a MASTER motor shaft member, thereby establishing at a subsequent instant of time a period of exact angular 55 synchronization between the shaft members whereupon the retardation of the SLAVE motor is stopped and the SLAVE motor shaft immediately resumes running at its predetermined normal rotational velocity which keeps it in exact angular synchronization with the MASTER 60 motor shaft member.
The teaching also shows several effective means for producing controllable retardation of the SLAVE motor shaft member rotational velocity.
Brought forth also is preferred control means for 65 accomplishing the essence of the invention which is both efficient at producing angular shaft position between several electric motors, and is low in cost.
These and other important improvements wrought by the instant invention will become apparent to the artisan in the ensuing description and claims.
DESCRIPTION OF DRAWINGS
FIG. 1 Electrical diagram for a preferred embodiment including the essence of the invention.
FIG. 2 Waveform representations for the electric signals effective at key circuit points in FIG. 1.
FIG. 3 Orientation of rotating motor synchronization shutter relative to an optical coupler module.
FIG. 4 Typical construction of MASTER motor synchronization shutter.
FIG. 5 Typical construction of SLAVE motor synchronization shutter.
FIG. 6 Electrical diagram for a preferred embodiment capable of synchronizing several (three) SLAVE motors.
FIG. 7 Electrical diagram continuation of FIG. 6 showing connection with MASTER and several SLAVE motors.
FIG. 8 Electrical diagram for a SLAVE motor control switch device.
FIG. 9 Partial electrical diagram for adapting the circuit of FIG. 1 to provide two levels of retardation of the SLAVE motor speed.
FIG. 10 Connection to provide HUNT and LOCK indicator lights.
FIG. 11 Adaptation for the circuit of FIG. 1 to provide interruption of power to the SLAVE motor to provide speed retardation.
FIG. 12 Adaptation for the circuit of FIG. 1 to provide mechanical drag or temporary overload of the SLAVE motor by an electric brake.
FIG. 13 Adaptation for the circuit of FIG. 1 providing magnetic sensing of shaft position.
FIG. 14 Adaptation for the circuit of FIG. 1 providing electrostatic sensing of shaft position.
FIG. 15 Adaptation for the circuit of FIG. 1 providing d.c. current through the 0B SLAVE motor winding, thereby producing electrodynamic drag and speed retardation.
DESCRIPTION OF THE INVENTION
The preferred embodiment for the instant invention appears in FIG, 1. Alternating current power is coupled into the apparatus on lines LI, L2. This power excites the MASTER synchronous motor 180, including the usual phase shift condensor 182. The master motor thus runs at a synchronous speed related to the a.c. power frequency by: