US2238614A - Electrical control system - Google Patents

Description

April 15, 1941. H. w. WILLIAMS ETAL 2,238,614

ELECTRICAL CONTROL SYSTEM Filed July 20, 1940 M wa aw Y (M? W m r f a w I WITNESS ES:

Patented Apr. 15, 1941 ELECTRICAL CONTROL SYSTEM Harold W. Williams, Nutley, and Danilo Santini,

Tenafly, N. J., assignors to Westinghouse 15180- tric Elevator Company, Jersey City, N. J., a corporation of Illinois Application July 20, 1940, Serial No. 346,540

11 Claims.

Our invention relates to electrical control systoms of the variable voltage type and, more particularly, to such systems of this character as include regulators and are suitable for the operation and control of elevator hoisting motors.

One object of the invention is to provide a variable voltage control system having a regulator which will respond more quickly to changes in the control operations than the systems heretofore used.

Another object is to provide a regulator so connected in a variable voltage system that it will operate without any sluggishness for controlling the generator of the system.

Another object is to provide a variable voltage control system embodying a regulator in which the regulator will influence the variable voltage system to give a normal degree of acceleration during a. normal run of an elevator car but which will give a greater than normal degree of retardation of the car during its deceleration to a stop.

A further object is to provide an elevator car control system which will give a normal degree of acceleration to the car during normal runs but which will give a greater degree of acceleration during leveling operations.

A further object is to provide a variable voltage control embodying a regulator which will prevent an elevator car from dropping slightly away from the floor at which it is stopped When it is being leveled upwards with a heavy load, in the event that the cables stretch sufficiently during the loading operation to require the car to be releveled.

It is also an object to provide for forcing the regulator of a variable, voltage system during predetermined operations of the system in order to secure more desirable operation of the system as a whole.

Other objects of the invention will be apparent from the following description taken in conjunction with the accompanying drawing, in which:

Figure 1 is a diagrammatic representation in straight line style of an elevator control system embodying our invention; and

Fig. 1A is an explanatory illustration of the relay embodied in the control system of Fig.

l. The illustration of the relays in Fig. 1A shows them with their coils and contact members disposed in horizontal alignment with their positions in the strai ht-line circuits of Fig. 1, so that the identification of any relay and the position of its coil and its contact members in the straight-line circuits of Fig. 1 may be readily returned.

Referring more particularly to the drawing, we have illustrated a suitable cable H as passing over a hoisting drum I2 for use in supporting an elevator car C. A hoisting motor i3 is provided for operating the hoisting drum by means of a shaft It to raise or lower the car, and a generator l6, driven by any suitable constant speed motor (not shown), is provided for supplying electrical energy to the hoisting motor. The genenator is usually designed to operate at 230 volts.

A regulating generator R (hereinafter called the regulator) is provided for exciting the generator and regulating its output. The regulator R is mounted on a shaft I! connected to the generator armature 16A so that the regulator will be driven at the same speed as the generator armature.

An electromagnetic brake [8, provided with a magnetizing coil His, is associated with the shaft M for stopping and holding the car when the power to the hoisting motor is cut off.

A car switch CS may be mounted in the car for use by the car attendant in causing the car to start and stop. The car switch is connected for operating a control system provided with a pair of supply conductors L+l and L-l, which may be connected, for energization, to any suitable source of supply. The field winding I3F of the hoisting motor is connected across the supply conductors L-l-l and L! to provide constant energization for the motor.

A variable voltage system of control is provided for controlling the operation of the hoisting motor l3 wherein the hoisting motor armature I3A is connected in a closed circuit 20 with the armature ISA of the generator I6. The generator is provided with a separately excited field winding iBF which is connected for energization in a loop circuit- 2! with the armature RA of the regulator B. so that the output of the generator and consequently the speed and direction of operation of the hoisting motor l3 may be controlled by controlling the operation of the regulator.

The regulator is provided with a self-excited field winding RCF, a pattern field winding RPF, a differential field winding RDF and a series field winding RSF.

The self-exciting field Winding RCF is connected in a loop circuit 2| in series with the regulator armature RA and the generator field winding ME. The total resistance of this circuit should be made equal to the volts that the regulator will produce when one ampere flows through its self-exciting field winding. In other words, the circuit is tuned so that perfect regulation will be obtained with no hunting effects.

The pattern field winding RPF is disposed to be connected across the supply conductors L-H L-i so that the generator voltage and the direction 01 the output of the regulator may be controlled by controlling the direction and the value of the current in the pattern field. For

given excitation of the pattern field, the regulator will produce a voltage which will excite the generator field winding As soon as current starts to fiow through the generator field winding circuit, the'self excitzhig field winding excites the regulamr to to ca current through the generator field v dlilerential 3. s connected es the terminals of the operator armature A rd in series with the ntlal. winding The differential with its resistor rd and the patwino'ing PUFF are designed to produce the same and opposite voltage in the regulator a given excitation of the pattern field. Under these conditions, the generator voltage will always build up to the value indicated by the pattern field. If, for any reason, a drop in voltage takes place in the generator that causes the norstrength of. the differential field to be less 5.--.1 that or" the pattern field, thus creating a voltage difierential in the regulator which, by the action or" its self-exciting field, will quickly and smoothly bring the generator voltage to the value indicated by the pattern field. In other words, the desired and the actual voltage in the generator will remain the same by reason of the efi'ect of the pattern field and the differential field, regardless of any load condition in the generator tending, to change the voltage. This means that by the use of the regulator in the manner indicated, we have not only applied exciting current to the generator field but also have corrected it for variations in the generator voltage, regardless f whether this variation is caused by armature reaction, saturation, resistance or brush drop.

As the current in the generator field increases, the excitation of the regulator differential field also increases, the strength of this field being such that when the generator reaches the voltage predetermined by the pattern field, the regulator stops building up, maintaining the required generator shunt field excitation to produce that voltage.

A shunt circuit 28 is disposed around the resistor 7'4 and so controlled by the high speed relay V, the forcing relay Q and the decelerating relay T that it shorts the resistor rd when the car is decelerating from normal high speed to a stop, thus providing a greater than normal excitation for the difl'erential field to produce a greater rate f retardation in the elevator than would be obtained with the normal differential field. The point at which the shorting of the resistor r4 takes place to secure a stronger differential field is when the speed relay V has been deenergized and the forcing relay Q and the decelerating relay T have not been deenergized.

The regulator series field RSF is connected in series in the loop circuit l'l between the armatures of the generator and the hoisting motor. A resistor rl is associated with the winding RSF and is connected in shunt relation thereto by an acceleration relay K while the car is making a normal run. The field winding RSI and its resistor rl are designed to cause the regulator to give the generator field winding 16F sufficient excitation to compensate for the RI drop in the hoisting motor. As the current increases in the armature of the generator, the voltage will rise just enough to overcome the RI drop of the current flowing through the hoisting motor armature. The net result will be a flat speed for the hoisting motor regardless of load and regardless of the selected value of that speed. Anything which tends to disturb this relation will be automatically compensated for by the reaction of the field windings previously described.

An up direction relay UH and a down direction relay DH are provided for connecting the pattern field to the supply conductors and for controlling the direction of the output of the regulator and thereby control the direction of operation of the car.

When the car is in normal operation in serving the floors and is not being leveled at a floor, the direction relays are controlled by an lip-direction switch U and a down-direction switch D, which are, in turn, controlled directly by the car switch CS, but when the car is stopping at a floor, the direction relays are controlled by a pair of levellug switches U25 and D26.

The elevator may be provided with any suitable leveling apparatus for causing the car to level at any floors at which it stops in case the cables stretch while the car is being leveled or the car moves away from the floor for any other reason while the stop is being made. In the present illustration, we have shown a very simple leveling apparatus comprising the up cam switch U26 and the down cam switch D26. The switches U26 and D% are mounted on the car in position to be operated by cams U21 and D2? at each floor. When the car makes a stop at the floor and moves below the fioor, the leveling switch U26 engages the up cam U27 and thereby energizes the up direction relay UH to cause the car to move upwardly until the cam switch slides off the upper end of the cam. If the car moves upwardly from its position level with the door, the down switch D26 will engage the cam UN and thereby energize the down direction relay DH to move the car downwardly until the switch D26 slides oil the lower end of the cam DZl. The circuit for the leveling switches is controlled by the gate relay contact G2 so that the leveling switches are effective only when the car has stopped at a floor and opened its gate (not shown). It is usual to provide means for withdrawing the leveling switches when the car passes a. floor at which no stop is to be made, but such details are old in the art and, therefore, are not included in the present diagram.

The speed of the elevator car during its normal runs is controlled by a high speed relay V operated by the car switch CS. The relay V controls the speed of the car by controlling a resistor r5 connected in the circuit of the pattern field RPF.

A gate relay G, controlled by the car gate, is provided for preventing floor to floor runs of the car and to condition the leveling system for operation while the gate is open. The gate relay is controlled by a cam switch 25 disposed to be closed by the closing of the gate and opened. by the opening of the gate, so that the gate relay will be energized only when the gate is closed.

ergize the field IBF of the generator, which causes A decelerating control relay P is provided for preventing the car on a normal run from being suddenly stopped, after the high speed relay V is deenergized, before its speed has decreased to a value low enough to permit an easy stop by deenergizing the generator and applying the brake. The relay P is a counter-electro'rnotive force relay connected across the loop circuit 20 so that it is responsive to the voltage of the generator, and it may be so designed that it will close its contacts when the generator voltage rises to 125 volts and to open its contacts when the generator voltage drops to '75 volts. In this manner, it is responsive to the speed of the car because the voltage of the generator and the speed of the car have a predetermined relation to each other.

The acceleration control relay K is provided for placing the resistor H in shunt relation with the regulator field winding RSF when the caris making a normal run in serving the fioors. The relay K is energized when either the up direction switch or the down direction switch is closed to run the car, and it thereupon closes self-holding contacts K2 which causes it to remain energized until the running relay M is deenergized when the car makes a stop. The relay K is energized only while the car is running and is not energized during a leveling operation and it maintains the re ulator field winding RSF in condition for normal running of the car.

The regulator forcing relay Q is provided for controlling the use of the resistor rd in connection with the regulator differential field winding RPF under certain conditions. The relay Q is a counter-electromotive force relay also connected across the loop circuit 20 so that it will respond to the voltage of the generator. The relay Q'is designed to open its contacts QR when the generator voltage rises to 100 volts and to open its contacts when the generator voltage falls to 50 volts.

The decelerating relay T, controlled by the running relay M and the high speed relay V, is provided for assisting in the control of the use of the resistor T4 in the circuit of the regulator differential field winding RDF.

It is believed that the invention will be better understood by the following assumed operation. It will be assumed that the car is standing at its lower terminal (not shown) and that the generator I6 and the regulator R are operating at constant speed and that the line switches have been closed to supply energy to the supply conductors L+I and L-I, thereby energizing the field winding 13F of the hoisting motor I3 and the gate relay G.

The rotation of the regulator armature RA does not affect the loop circuit 2I or the generator field winding IBF because, as before stated, the selfexciting field winding RCF of the regulator is so designed that it generates just sufilcient voltage to send the current through the loop circuit in which the generator field winding is disposed. Hence, the generator field winding is not energized and the generator does not now supply any current to the hoisting motor.

It will be assumed now that the attendant in the car moves the car switch CS in counter-clockwise direction to cause the car to move upwardly.

Briefly, the movement of the car switch for up direction energizes the up direction switch U, which energizes the up direction relay UH and the running relay M to energize the pattern field RPF and release the brake I8. The energized pattern field RPF causes the regulator R to enthe generator It to generate current to energize the hoisting motor I3 and thereby move the car upwardly. i

This operation, in detail, is as follows: The movement of the car switch closes the contact members CSI and CS2 to energize the up direction switch U by the circuit: L+I, CS. CSI, CS2, U, DI, GI, 3|, LI. The energized up direction switch U closes its self-holding contact members UI, closes its contact members U3 and- U4. and opens its contact members U2.

The closing of the contact members U3 energizes the acceleration control relay K by the circuit: L+, K, U3, L.

The energized relay K closes its self-holding contact members K2 and its contact members KI for connecting the resistor H in shunt with the field winding RSF so that that field will be energized in its normal manner during the normal run of the car to its next stop.

The closing of the contact members U4 energizes the up direction relay UH and the running relay Mby the circuit: L+, U4, UH, DH3, M, L. The energized relay M releases the brake I8 and prepares other circuits for operation. The energized relay UH closes its contact members UHI and UH2 and opens its contact members III-I3. The closed contact members UHI and UH2 energize the pattern field RPF by the circuit: L+, UHI, RPF, UH2, r5, L As soon as current starts to fiow through the pattern field circuit, the regulator field RCF' self excites the regulator to force current through the generator field. As the current in the generator field increases, the excitation of the regulator differential field RDF also increases, the strength of this field being such that when the generator reaches the voltage predetermined by the pattern field, the regulator stops building up and maintains the required generator field winding excitation to produce that voltage. The excitation of the generator field ISF causes its armature IGA to supply the required amount of current for operating the hoisting motor I3 through the loop circuit 20 which connects the armatures of the generator and the hoisting motor.

When the car switch was thrown to the up position, it also closed its contacts CSI and CS3, thereby energizing the high speed relay by the circuit: L+, CSI, CS3, V, GI, 3I, L. The high speed relay V now opens its contact members VI and closes its contact members V2. The closing of the contact members V2 short circuits the resistor 15 in the circuit of the pattern field winding RPF and thereby increases the energization of that field winding to increase the current supplied by the regulator to the generator field Winding, thus causing the car to follow a normal acceleration until it reaches its normally high speed, after which it continues to run at a constant speed until it is decelerated for a stop.

If for any reason the loading on the car affects thev hoisting motor sufiiciently to cause a drop in the voltage of the generator, the strength of the regulator differential field will be less than that of the pattern field and the voltage differential will be set up in the regulator, which by the action of its self-exciting field, will quickly and smoothly bring the generator voltage to the value indicated by the controller or pattern field.

Furthermore, as stated before, the regulator series field winding RSF will cause the regulator R to give the generator field winding IBF sufficient excitation to compensate for the RI drop in the hoisting motor l3 and the net result will be a constant speed for the hoisting motor regardless of the load and regardless of the selected value of that speed, and everything which tends to disturb this relation will be automatically compensated for by the reaction of the field windings as previously described.

As soon as the generator voltage rises to a predetermined value, say, '75 volts, the relay P is energized to close its contact members Pl in the holding circuit for the up direction switch U for the purpose of preventing deenergization of that switch to stop the car until after the car is decelerated to a suitable stopping speed by the high speed relay V when making the next stop.

As the generator voltage rises further to, say, 100 volts, the relay Q is energized to close its contact members Q'l in the shunt circuit around the resistor rl but that'does not affect the resistor at this time because the contact members Vi in that circuit are now open. However it helps to prepare that circuit for operation when the car is decelerating to a stop.

At the time the high speed-relay was energized it closed its contact members V3, thereby energizing the decelerating relay T by the circuit: L+, M2, T, V3, L. The energized relay T closes its self-holding contact members T2 and also its contact members Tl in the shunt circuit 29 to help prepare that circuit for operation when the car is to be decelerated to a stop. The

relay T now stays energized until the car is stopped.

The car is now moving up the hatchway at its normal high speed and we shall assume that it approaches a floor at which the attendant desires to make a stop, and that he thereupon moves the car switch CS to open its contact members CS! and 053,150 decelerate the car from high speed to a stopping speed.

The opening of the contact members CS! and CS3 deenergizes the high speed relay V, which in turn opens its contact members V2 and thereby reinserts the resistor T5 in circuit with the pattern field RPF. The inclusion of the resistor '5 in this field winding decreases its energization and thereby causes a corresponding decrease in the output of the regulator R to the loop circuit 2 I, including the generatorfield winding IGF. The decrease in the energization of the generator field winding causes the generator armature to supply less current to the hoisting motor and thereby decreases the speed of the car.

It should be noted here that the effect of the decreased current flowing in the loop circuit 2t causes the differential field winding RDF of the regulator to be so changed in energization that it cooperates with the pattern field to cause the regulator to quickly and smoothly bring the generator voltage down to the value indicated by the pattern field.

The deenergized high speed relay V closes its back contacts Vi shunt circuit 29 around the resistor rd because the contact members Ti and Qi of thedecelerating relay T and the regulator forcing relay Q are still closed. The shortcircuiting of the resistor M by the closed shunt circuit 2Q gives a greater than normal excitation of the differential field RDF. This produces a rate of retardation in the elevator considerably greater than would be obtained with the normally excited difierential field. This stronger differenand thereby completes the tial field is maintained while the car is decelerating until the relay Q becomes deenergized.

As the speed of the car decreases, the generator voltage decreases and, when the generator voltage decreases to a predetermined low voltage, say, 50 volts, the relay Q is deenergized to a point Where it opens its contact members Q! and thereby relnserts the resistor rd in the circuit of the differential field. This is, of course, at a relatively low voltage and, therefore, at a relatively low speed of the car, and during the time the shunt circuit remained closed, the car was very effectively retarded in a manner very desirable in controls of various types of which this is one embodiment.

When the generator voltage dropped to a predetermined voltage, say, 75 volts, the relay P was sufiiciently deenergized to open its contact members Pl in the self-holding circuit of the up direction switch U, thus leaving the circuits of that switch so arranged that it may be deenergized at any time by the centering of the car switch. Thus it is seen that the provision of the relay P prevents the direction switch from being deenergized to stop the car immediately after the relay V is deenergized to decrease the speed of the car, It is a safety device to prevent the sudden stopping of the car while it is running at its normal high speed.

It will be assumed now that the car arrives within stopping distance of the floor at which the stop is to be made, that it has decelerated to its stopping speed, and that the attendant moves the car switch to its center position, thus open-- ing the contact members CS2 and CS2 to stop the car at the fioor desired. The opening of the contact members 0st and CS2 deenergizes the up direction switch U, which, in turn, opens its contact members Ul, U3 and U4 and closes its back contact members U2.

The opening of the contact members U4 deenergizes the up direction relay UH and the running relay M. The deenergized relay UH opens its contact members UHI and UH2, thus deenergizing the pattern field RPF. The deenergization of the pattern field causes the regulator to stop supplying voltage to the generator field winding iGF, which, in turn, causes the generator armature "SA to stop supplying current to the hoisting motor i3, so that it stops moving the car.

The deenergization of the running relay M opens its contact members Ml, M2 and M3. The opening of the contact members Ml deenergizes the brake coil I81; and causes the brake Hi to stop the car and hold it at the floor. The opening of the contact members M2 deenergizes the decelerating relay T to open its contact members Tl in the shunt circuit 29 around the resistor M. The opening of the contact members M3 opens the self-holding circuit of the acceleration control relay K, which, in turn, opens its contact members Kl and removes the resistor ri from its shunt relation to the series field winding RSF so that winding will eifect a more rapid acceleration of the output of the regulator than normal if a leveling operation takes place while the car is stopping at the floor.

The car is now standing at the floor and it will be assumed that the attendant opens the car gate (not shown) and proceeds to load the car, The opening of the car gate opens the gate switch 25, thus deenergizing the gate relay G to open its contact members GI and close its contact members G2. The opening of the contact members GI prevents the direction switches from being energized to start the car on a normal run while the gate is open. The closing or the contact members (32 prepares the leveling system for operation it a leveling operation is necessary while the car is at the floor.

It will be assumed now that the load taken on the car causes the cables to stretch, thus causing the car to sink below the level of the fioor at which it is stopped. As the car starts to move downwardly it causes the switch U26 to engage the cam U21. This closes the switch U26, thus energizing the up direction relay UH to return the car upwardly to a position level with the floor at which it is stopped. The circuit of relay UH extends: L+, G2, U26, UH, DH3, M, L.

It will be noted that the running relay M is also energized by this circuit to close its contact members Ml, thus releasing the brake [8 so that the car may be moved upwardly.

The energized relay UH closes its contact members UHI and UI-H, thus energizing the pattern field RPF to move the car upwardly as described previously in connection with the normal fioor to floor run. However, in this leveling operation, the up direction switch U is not energized and the resistor rl is not connected in shunt relation to the series field winding RSF, thus causing the full current of the generator to pass through the series. field winding RSF. The full current of the generator causes a much stronger vexcitation or-the series field winding during the leveling operation than-occurs during the normal running operation of the car. This condition is normally considered as over compounded but we have found from experience that the regulator may be over compounded during leveling operation and that we thereby secure a quick response and rapid acceleration in the leveling operation.

As the car is moved upwardly in the leveling operation, the switch U26 leaves the cam U21 as the car levels with the fioor and is thereby opened to deenergize the up direction relay UH and the running relay M. The deenergized relay UH opens its contact members UHI and UH2, thus deenergizing the pattern field RPF to stop the car and the deenergized relay M opens its contact members MI and thereby applies the brake l8 to hold the car in its fioor level position.

By the foregoing description it will be seen that we have provided a variable voltage system of control embodying a regulator which gives a normal rate of acceleration and a desirable rate of retardation for a car during a normal floor to fioor run and which provides a quick response and rapid acceleration during leveling operations.

Although we have illustrated and described only one specific embodiment of our invention, it is to be understood that many changes therein and modifications thereof may be made without departing from the spirit and scope of the invention.

We claim as our invention: I

l. A variable voltage system comprising a, power generator having an armature and a field winding and a motor connected in a loop circuit with said armature, a regulating generator for energizing the field winding of the power gen- ,erator, said regulating generator having an armature and a plurality of field windings including a series field winding connected to carry a portion of. the current fiowing in the loop circuit connecting the power generator armature and the motor, and a. differential field winding connected across the terminals of the power generator armature, a control means for the system, and

7 means responsive to one operation or the control means for increasing the value of the series field winding to cause a greater than normal rate 'of acceleration of the motor and responsive to another operation of the control means for increasing the value or the-differential field winding to cause a greater than normal retardation of the motor. 4

2. A variable voltage system comprising a power generator having an armature and a field winding and a motor connected in a loop circuit with said armature, a regulating generator for energizing the field winding of the power generator, said regulating generator having an armature and a plurality of field windings including a series field winding connected to carry a portion of the current flowing in the loop circuit connecting the power generator armature and the motor, and a diflerential field winding connected across the terminals of the power generator armature, a controlmeans for the system, and means responsive to one operation of the control means for increasing the value or the series field winding to cause a greater than normal rate of acceleration of the motor.

3. A variable voltage system comprising a power generator having an armature and a field winding and a motor connected in a loop circuit with said armature, a regulating generator for energizing the field winding of the power generator, said regulating generator having an armature and a plurality of field windings including a series field winding connected to carry a portion of the current flowing in the loop circuit connecting the power generator armature and the motor, and a differential field winding connected across the terminals of the power generator armature, a control means for the system, and means responsive to one operation of the control means for increasing the value of the diilerential field winding to cause a greater than normal retardation of the motor.

4. A variable voltage system for operating an elevator car comprising a power generator provided with an armature and a field winding and a motor connected in a loop circuit with said armature, a regulating generator for energizing a field winding of the power generator; said regulating generator having an armature, a series field winding connected to carry at least a portion of the current flowing in the loop circuit connecting the power generator and themotor, a difi'erential field winding connected across the terminals of the power generator armature, a sellexciting field winding connected in loop circuit with the power generator field winding and the regulating generator armature, and a pattern field winding connected to an external supply of electrical energy for controlling the output of electrical energy by the regulating generator to the power generator; a control means for causing the motor to accelerate or decelerate the car, means responsive to operation of. the control means in accelerating the car for a normal run for causing one degree of excitation of the series field winding to produce a normal rate of acceleration of the car while it is on a normal run and responsive to operation of the control means in leveling the car at a floor for causing a greater degree of excitation of the series field winding to secure a greater than normal rate oi. acceleration or the car while it is being leveled.

5. A variable voltage system for operating an elevator car comprising a power generator provided with an armature and a field winding and a motor connected in a loop circuit with said armature, a regulating generator for energizing a field winding of the power generator, said regulating generator having an armature, a series field winding connected to carry at least a portion of the current flowing in the loop circuit connecting the power generator and the motor, a differential field winding connected across the terminals of the power generator armature, a self-exciting field winding connected in loop circuit with the power generator field winding and the regulating generator armature, and a pattern field winding connected to an external supply of electrical energy for controlling the output of electrical energy by the regulating generator to the power generator, a control means for causing the motor to start, accelerate, run, decelerate and stop the car, and means responsive to operation of the control means in starting, accelerating and running the car for causing a normal excitation of the difierential field winding and responsive to operation of the control means in decelerating the car for causing a greater than normal excitation of the differential field winding to secure an increased retardation of t e car when it is decelerating to a stop.

6. A variable voltage system of control comprising a power generator provided with an armature and a field winding and a motor connected in a loop circuit with said armature, a regulating generator for energizing a field winding of the power generator, said regulating generator having an armature, a series field winding connected to carry at least a portion of the current flowing in the loop circuit connecting the power generator and the motor, a differential field winding connected across the terminals of the power generator armature, a self-exciting field winding connected in loop circuit with the power generator field winding and the regulating generator armature, and a pattern field winding connected to an external supply of electrical energy for controlling the output of electrical energy by the regulating generator to the power generator, a resistor associated with the series field winding for controlling the degree of excitation of that winding, a resistor associated with the differential field winding for controlling the degree of excitation of that winding, and a control means for rendering the first named resistor effective for one rate of acceleration of the motor and ineffective for another rate of acceleration of the motor and for rendering the second named resistor effective when the motor is accelerating and for rendering it ineffective when the motor is decelerating,

7. A variable voltage system for operating an elevator car having a car gate, said system comprising a power generator provided with an armature and a field winding and a motor connected in loop circuit with said armature; a regulating generator for energizing the powergenerator field winding, said regulating generator having a plurality of field windings, including a series field winding connected in the loop circuit in series with the power generator armature, a resistor associated with the series field winding, means responsive to the closed position of the car gate when the car is being moved in a fioor to floor run for controlling the resistor to cause a normal excitation of the series field winding and responsive to the open position oi the car'gate when the car is being leveled for controlling the resistor to cause a greater than normal excitation of the series field winding.

8. A variable voltage system for operating an elevator car, said system comprising a power generator having an armature and a field winding and a motor connected in loop circuit with said armature; a regulating generator for energizing the power generator field winding, said regulating generator having a plurality of field windings including a difi'erential field Winding connected across the loop circuit in series with the power generator, means for controlling the connection of the regulating generator to a source of electrical energy for causing it to efiect the start ing, running, deceleration and stopping of the car, and means responsive to operation of the control means in decelerating the car for causing the differential field winding to receive a greater degree of excitation while the car is being decelerated than it'receives when the car is being accelerated to thereby increase the retardation of the car,

9. A variable voltage system for operating an elevator car, said system comprising a power generator having an armature and a field winding and a motor connected in loop circuit with said armature; a regulating generator for energizing the power generator field winding, said regulating generator having a plurality of field windings including a differential field winding connected across the loop circuit in series with the power generator, means for controlling the connection of the regulating generator to a source of electrical energy for causing it to eifect the starting, running, deceleration and stopping of the car, means responsive to the operation of the control means in decelerating the car for causing the differential field winding to receive a greater degree of excitation while the car is being decelerated than it receives when the car is being accelerated to thereby increase the retardation of the car, and a counter-electromotive force relay connected across the loop circuit for controlling the period during which the differential field winding receives said greater degree of excita tion.

10. A variable voltage system for operating an elevator car, said system comprising a power generator having an armature and a field winding and a motor connected in loop circuit with said armature; a regulating generator for energizing the power generator field winding, said regulating generator having a plurality of field windings including a differential field winding connected across the loop circuit in series with the power generator, means for controlling the connection of the regulating generator to a source of electrical energy for causing it to effect the starting, running, deceleration and stopping of the car, means responsive to operation of the control means in decelerating the car for causing the differential field winding to receive a greater degree of excitation while the car is being deceler- 11. A variable voltage system of control for operating an elevator car, said system comprising a power generator provided with an armature and a field winding, a. motor connected in a loop circuit with said armature, and a regulating generator, said regulating generator having an armature and a plurality of field windings including series field winding and a differential field winding; a pair of direction switches for causing the car to make a floor to floor run, a pair of leveling switches for causing the car to level at a floor at which it is stopped, means responsive to operation of a direction switch in moving the car for causing the series field winding and the diiierential field. winding to have predetermined normal degrees of excitation while the car is accelerating during a floor to floor run,

means responsive;- to operation of a directionswitch to decelerate a car for causing the dinerential field to receive a greater than normal degree of excitation, and means responsive to operation oi! a leveling switch and the inactive position of the direction switches for causing the series field winding to receive a greater than 10 normal excitation while the car is being leveled.

HAROLD W. WILLIAMS. DANILO SANTLNI.

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