Single-phase full-wave regenerative scr shunt motor control system

Claim 2

In a single-phase full-wave rectified regenerative system for controlling power to a D.C. motor to control the speed thereof, the combination comprising: an alternating current power supply circuit; forward controlled rectifiers for controlling full-wave rectified power from said power supply circuit to the motor; regenerative controlled rectifiers for controlling regeneration of power from the motor back to said power supply circuit when the motor counter voltage exceeds the supply voltage; said forward and regenerative controlled rectifiers being connected in a bridge circuit having a first pair of terminals connected to opposite sides of said power supply circuit and having a second pair of terminals; a T-network of reactors; means connecting the lateral reactor of said T-network across said second pair of terminals of the bridge circuit to prevent a short circuit across said power supply when forward and regenerative controlled rectifiers connected to the respective sides of said power supply conduct simultaneously; circuit means connecting the other reactor of said T-network and the motor in series to a center tap of said power supply circuit; and firing control means for controlling the firing angles of said forward and regenerative controlled rectifiers and including means affording a minimum firing angle therefor.

Claim 3

The invention defined in claim 1, wherein said firing control means comprises: a pair of regulators including a forward running control regulator for controlling firing of said forward controlled rectifiers and a regenerative control regulator for controlling firing of said regenerative controlled rectifiers; and each said regulator comprising: a pulse generator for applying firing pulses to the respectively associated controlled rectifiers; and means for developing a current reference signal to control advance of the firing angle from a predetermined value comprising: signal mixing means for mixing a plurality of control signals to control the value of said current reference signal; said firing control means also comprising current feedback means for deriving a current signal proportional to the motor current and for transmitting said signal as a single polarity current feedback signal regardless of the directioN of motor current and for subtracting said signal from the current reference signal in each of said regulators; and said regulators being identical except for the polarity connections of said control signals to said signal mixing means.

Claim 4

The invention defined in claim 1, wherein said firing control means comprises: a pair of regulators including a forward running control regulator for controlling firing of said forward controlled rectifiers and a regenerative control regulator for controlling firing of said regenerative controlled rectifiers; and each said regulator comprising: a pulse generator for applying firing pulses to the respectively associated controlled rectifiers; increased minimum firing circuit means for controlling said pulse generator to apply firing pulses at a predetermined minimum firing angle that cannot be decreased by the regulator; and means for developing a current reference signal to control advance of the firing angle from said minimum value comprising signal mixing means for mixing a reference signal and a speed feedback signal to control the value of said current reference signal; and said firing control means also comprising a current feedback circuit connected to said motor circuit means for developing a single polarity current feedback signal regardless of the polarity of the motor current and for subtracting said current feedback signal from said current reference signal to provide a resultant signal for controlling said pulse generator.

Claim 5

The invention defined in claim 3, wherein said signal mixing means also comprises: means for mixing a current compensation feedback signal with said reference and speed feedback signals to control the value of said current reference signal.

Claim 6

The invention defined in claim 4, wherein: said regulators are identical except for the polarities of said signals applied to said signal mixing means.

Claim 7

The invention defined in claim 1, wherein: said lateral reactor and said other reactor of said T-network are the same size as to inductive capacity.

Claim 8

A single-phase full-wave rectified regenerative system for controlling power to a D.C. shunt motor armature to control the motor speed comprising: an A.C. power supply means; a T-network of reactors including a first reactor connected at one end to the middle of a lateral reactor; circuit means connecting the other end of said first reactor through the motor armature in series to an intermediate voltage point on said power supply means; a pair of forward controlled rectifiers connected between said power supply means and one end of said lateral reactor for controlling power to the motor armature; a pair of regenerative controlled rectifiers connected between the other end of said lateral reactor and said power supply means for controlling regeneration of power from the motor armature back into said power supply means; a forward regulator for controlling the firing of said forward controlled rectifiers including means affording a minimum firing angle on each half-cycle that cannot be reduced and means for variably advancing the firing angle from said minimum value to control the motor speed; and a regenerative regulator for controlling the firing of said regenerative controlled rectifiers including means affording a minimum firing angle on each half-cycle that cannot be reduced and means operable when the motor counter voltage exceeds the supply voltage for advancing the firing angle from said minimum value to control regenerative braking of the motor.

Claim 9

A single-phase full-wave rectified regenerative system for controlling power to a D.C. shunt motor armature to control the motor speed comprising: an A.C. power supply means; a T-network of reactors including a first reactor connected at one end to the middle of a lateral reactor; circuit means connecting the other end of said first reactor through the motor armature in series to an intermediate voltage point on said power supply means; a pair of forward controlled rectifiers connected between said power supply means and one end of said lateral reactor for controlling power to the motor armature; a pair of regenerative controlled rectifiers connected between the other end of said lateral reactor and said power supply means for controlling regeneration of power from the motor armature back into said power supply means; a forward regulator for controlling the firing of said forward controlled rectifiers including means affording a minimum firing angle on each half-cycle that cannot be reduced and means for variably advancing the firing angle from said minimum value to control the motor speed; and a regenerative regulator for controlling the firing of said regenerative controlled rectifiers including means affording a minimum firing angle on each half-cycle that cannot be reduced and means operable when the motor counter voltage exceeds the supply voltage for advancing the firing angle from said minimum value to control regenerative braking of the motor.

Claim 10

The invention defined in claim 7, wherein said system also comprises: a current detecting device in said motor circuit means; and a current feedback circuit connected to said current detecting device for applying to each of said regulators the same polarity current feedback signal regardless of the direction of motor current.

Claim 11

A single-phase full-wave regenerative SCR system for controllinG a D.C. shunt motor comprising: an A.C. power supply circuit having a center tap; a T-network of reactors comprising a lateral reactor connected at its middle to one end of a series reactor; circuit means connecting said series reactor at its other end in series with the motor armature to said center tap on the power supply circuit; a pair of forward SCR''s connected between the respective sides of said power supply circuit and one end of said lateral reactor for controlling forward running power to the motor armature; a pair of regenerative SCR''s connected between the other end of said lateral reactor and the respective sides of said power supply circuit for controlling regeneration of power from the motor armature back into said power supply circuit; a forward firing control regulator for the forward SCR''s and a regenerative firing control regulator for the regenerative SCR''5; each said regulator comprising means affording a minimum firing angle for the respectively associated SCR''s that cannot be reduced by regulation; each said regulator also comprising means for providing a controllable current reference signal for advancing the firing angle of the respectively associated SCR''s from the minimum value; means common to said regulators effective when the current reference signal in one regulator is being increased for decreasing the current reference signal in the other regulator; and current feedback means for deriving a signal proportional to motor current from said motor circuit means and for applying a unidirectional current feedback signal to each of said regulators.

Claim 12

A single-phase full-wave regenerative SCR system for controllinG a D.C. shunt motor comprising: an A.C. power supply circuit having a center tap; a T-network of reactors comprising a lateral reactor connected at its middle to one end of a series reactor; circuit means connecting said series reactor at its other end in series with the motor armature to said center tap on the power supply circuit; a pair of forward SCR''s connected between the respective sides of said power supply circuit and one end of said lateral reactor for controlling forward running power to the motor armature; a pair of regenerative SCR''s connected between the other end of said lateral reactor and the respective sides of said power supply circuit for controlling regeneration of power from the motor armature back into said power supply circuit; a forward firing control regulator for the forward SCR''s and a regenerative firing control regulator for the regenerative SCR''5; each said regulator comprising means affording a minimum firing angle for the respectively associated SCR''s that cannot be reduced by regulation; each said regulator also comprising means for providing a controllable current reference signal for advancing the firing angle of the respectively associated SCR''s from the minimum value; means common to said regulators effective when the current reference signal in one regulator is being increased for decreasing the current reference signal in the other regulator; and current feedback means for deriving a signal proportional to motor current from said motor circuit means and for applying a unidirectional current feedback signal to each of said regulators.

Claim 13

The invention defined in claim 9, wherein: said lateral reactor of said T-network has a large enough inductance to protect the SCR''s from cross-the-line conduction; and said series reactor of said T-network has a large enough inductance such that in the aforesaid system that includes said minimum firing angle continuous current condition is reached at a desired point determined by motor heating characteristics and maximum tolerable change of system''s gain.