US1915737A - Hoist control system for electric shovels - Google Patents

Description

June 27, 1933. JACOBS HOIST CONTROL SYSTEM FOR ELECTRIC SHOVELS Filed April 26, 1929 11v VENTOR ATTORNEY v Patented June 27, 1933 UNITED STATES PATENT OFFICE HENRY S.JACOBS, or amnion, on 'o, ASSIGNOR TO THE MARION s rnnn SHOVEL comnew, or MARIOH, care, A conronnrron 01" 01110 HOIS'I' CONTROL SYSTEM FOR ELECTRIC SHOVELS Application filed April 26,

It is the object of my invention to provide anelectrical control; system particularly adapted for electrically driven excavating equipment,such as shovels.

It is the object of my inventlon to provide an electrical control system for the hoistmg of the dipper. and for the crowding of the dipper into the material to be hoisted so that the motion'which raises the dipper through vthe bank and the motion which forces the V dipper into thebankwill be eiiected with electrical equipment having the following desired characteristics. ISuch characterlstlcs are the capaclty for very quick starting, that is high speed acceleration of the electrical equipment; the

bringingof the hoist or crowd motor up to speed in the most satisfactory fashion; the

operation of theho'istor the crowd mechanism by a "single controller with a single handle so that one continuous movement of the operator Will bring the shovel into full operation; the imaintenancc of very high speeds when the load is light so as to lift the lightload at high speed; the ability to lift a'heavy load at low speed; and the ability f to exert'thelmaximum pull 'at stall without undue mechanical or electrical strains.

It is a further object to provide equipment having such characteristics with the accompanying characteristics of long life of the motors, decreased -maintenance costs, de-

'livered by the motors.

creased lost time, decreasedpower consumption per; unit of work done and a betterrelationship between the speed andltorque dei provide electrical control equipment ofsuch small size and compact nature that there is not only economy in cost but in the space occupied which is a material factor on an electric: shovel where thefioor space is eX- tremely limited; I l' Itis a particular object of my invention to reduceithe 'extent of excessheating of the control equipment. a V

1923. Serial No. 355,362.

It is an object to provide for smoother acceleration otthe motor, better commutation of the motor and generator and less severe mechanical and electrical strains on the equipment.

In particular it is my object to furnish a low inductive generator shunt field with a corresponding low resistance field Winding; means for reducing voltage of the generator immediately jprior'to placing the motor on thecircuit in order to decrease the current inrush of the motor whenthe motor armature circuit is closed; and the raising of the generator voltage by proper field control while simultaneously cutting out starting resistance. The results of these particular objects arethe utilization of a generator circuit, a motor circuit and a field bleeder circuit preferably associated with permanent resistors and a variable armature resistance in the motor circuit. Q l

i It is my object to prevent poor commutation on the motor and generator; to prevent excessive and unnecessary heatingof both the motor and generator; to prevent excessive possible a decreased amount of ohmic resistance in the starting resistor; to make possible a more rugged mechanical'resistor construction for a given space and which can use cheaper material and to provide higher speeds and higher generator voltage with the same starting resistance and same mechanical and electrical strains. i

It is my object to provide a field bleeder circuitimproved upon the generator and motor circuit for suitably raising and lowering the voltage in the circuit. y

It is my object to employ a suitable resistor o prevent sudden inrushes of current in the motor when the controller is moved quickly to cut out all starting resistance, and it is my object to provide a suitable" resistor for governing-the amount ofjgenerator voltage reduction when the primary switches are closed. y 7

It is my object to provide a balancing of voltages through the equipment and circuits I provide for effecting the above objects.

. l changes. Hencefl ihn the'generator $603+; afiowihg the necked with the motel-through the aka ,andQcwyrd circuit; resistor and this lmktg-e is (311ml?) witl1hq-.gw Mp1: step eratrvo talga mt o 50*0- M 95 the 1y $3 2,111; cuttinfiut' the I, 13W f. it em 'ntclumeiinlat RLHBQVQIE'B R gm.

,bit

starting-resistance is cut out the inrush current'wouldat that time, be equal to the initial iiha'i'sh'current; The-following steps of rcsistan'cecah then be cutout'in exactly the same fasl'fion unt-il all the resistance has been cut out except that which constitutes the permanent resistance the circuit.

. ,,Hence, Ihnd that byproviding a genera- "circuit, a inotor circuit connected thereto,ableeder. circuitconnected into the motor and the generator circuit and resistance of permanentcharacter inassociation with the variable; resistor in theniotor field *ircu'it, I, aura enabled to so. adjust the conditions of the circuit-s'as to} secure quick starting, high spec/d withslight loads, low speed with heavy 10m and mazriinum pull atstall.

The generator circuit is comnosod of a -r l l circuitjust described is always hot and the di- TlllS is the generator current istl aveling iii the direction ircated by tlie arrows. circuit,

Mofor oirc uit a I HM indicates the hoist motor. The hoist motor is provided on one side with the lead 1 13 that connects the motor toits commutatiz'i'g field 131-. {This commutati nglfield is connect-'- ed to the permanent resistorf15. This side of the motorcirc'uit is adapted to be connectei fo' t'he generator cir 1 it the primary switch AA. .This switch is reversible switch.v It isint'erconnected with and adapted to be simultaneously operated with the second of the primary switches,designated A.

, q Blceder circuit a v The bleecle'r circuit is connected by the lead 16 *tofthe hoist motor. I On the other side it is connected to the leadl? that forms a part of th'ebleed er circuit, the other side of which is connectedby the wire '18 to the terminal 19 in the generator circuit? Between the wires 17 and18 is located the permanent resistance 20. This combined motor commutation field circuit Y and the bleeder circuit having been simultaneously connected tov one another and to the-generator circuit by the closing of the primary switches AA and; 1A are now in a position to be connected tothejserles field rnotor circuit andxthe variable res stance.

Motor series field circuit and variable resista Y once The switch'B is the secondary switch which is closed after the switches A and AA have been simultaneously closed. AA is a reversible switch. Upon the closing of the switch B the bleeder circuit and the commutating field circuit of the motor have been connected with the series field circuit of the motor. Thereupon, the lead 21 connects the variable resistance 22. This resistance is provided with the slide wire base terminal 23 and typ ical stages of resistance 24, 25, 26, 27, 28 and 2-9.: 30 indicates the slide wire contact member. 31 indicates the lead that connects this circuit into the series held 32 of the motor and 33 indicates the lead that connects the. series field to the terminal 3 in the generator circuit. I

The variable resistance 22 is a progressive resistance, the resistance steps increasing as the movable member 30 progresses from 29 to 23 tothereby give a more nearly uniform heating in the controller.

Field Header circuit circuit proper but when the bleed circuit opcrates itembraces and is composed of,,in effect, the standard motor commutating circuit heretofore described, such as from AA, 15, 14, 13, HM and 16 with switch A.

C'urre'nt directions The current in the generator circuit never changes direction. hen all. switches are closed, due to the difference in potential between the points 3e and 19 the current flowsqoo through switch A, 17, resistor 20, 18, 19 and (315 into the" generator circuit for the purposes hereinafter. described.

The series field circuit of the motor is arranged that the current travels in the direction 31, 29 through theresistor 22,: 21, switchB and thence into the circuits hereinbeicre mentioned and described.

Relative voltages At certain important points in the system, the voltages vary and this difference in potential at these points is essential to the operation of my circuits and apparatus. The voltages I indicate are merely typical and not exclusive. Assuming a. given motor load of" j alu As the slide wire "30 proceeds from the middle point ofthe resistance 22 towards 29 the blee er circuit raises the generator circuit voltage above normalto give the motor a Thegmotor' has now been given the proper torque. It is now necessary to give the mohi her maximum speed than otherwise postor speed. This is done by cutting out the steps of resistance as indicated which raises the voltage applied to the motor causing it to generate a higher voltage and to rotate at higher speeds as the counter voltage of the motor rises and the difference in voltage be-' i a) tween 34 and 19 decreases which reduces the amount of current shunted out of field 7 thereby raising the generator voltage. The increasing voltage applied to the motor for increasing thespeed is then due to a combiv nationof cutting out the resistance 22 and the raising of the generator voltage due to the bleeder circuit connections.

' Hoistmotor stop operation To stop the hoist motor the reverse operation of handling the starting'switches is ef- .fe'cted. This is done by first cutting in, in succession, all parts of the variable resistance 22 until the slide wire has reached r 23. Switch B is then opened and then switches A and AA are opened together.

M Resistance 15 When the vpermanent resistance 15 is in line'theheating on the hoist controller is decreased by the reduction of the arc. The presence of the resistance 15 gives the same effect as a greater number of steps in the resistance 22 withja decreased are without increasingthe size or changing the design of the controller. The greater the number of steps the smaller the are so that I secure the same effect in a simpler, more compact and cheaper mannerbythe utilization of the resistance 15as located. Itis possible to employ a'smallerland more compact controller of less expensive character while at the same time, decreasing the heating of material and increasing the life of the entire equipment.

' Characteristics ofge'nel'dtor field 7 e In accomplishing my invention, I employ a. low inductive and low resistance field windingof the. generator, such as 7. I prefer to vuse a generator with "a drooping voltage characteristicr H Switches AA and field bleeder circuit 1 The arrangement of the switches AA and the field bleeder circuit is for the purpose of reducing voltage for the enerator immediately priorto throwing t e. hoist motor on the circuit in order to decrease the current inrush of the hoist motor when its armature circuit is closed by closing the switch B. This has the following factors: i

'(1) Bad commutation on the hoist motor and generator is eliminated.

(2) The arrangement prevents excessive and unnecessary heating of both the generator and. the hoist motor.

(3) It prevents excessive mechanical and electrical strains. 1

(4) It makes possible a decreased amount of resistance in the starting resiston' (5) It makes possible a morerugged mechanical resistor construction for a given space and makes possible the use of cheaper material,

(6) It makes possible higher speeds and higher generator voltage with the samestarting resistance and with the same mechanical and electrical strains.

Switch B and the slide wire variable.

. resistance The purpose of this arrangement of switch B and the slide wire variable resistance is to begin raising the generator voltage by field control while simultaneously cutting out the starting resistor. The bleeder circuit is used to raise as .well as to lower voltage at the switch, B. V

Resistors 15 and 20 The resistor 15 is used to prevent the inrush of current on the motor when the controller is moved quickly to cutout all the resistance. Resistor 15 for that purpose is made equal to the resistance of the motor.

The resistor 20 governs the amount of the generator'voltage reduction when switches A and AA are closed.

While the apparatus is designed primarily for the operation and functions which have been described I wish it to be understood thatthe so-called bleeder circuit (17 18-19) is also capable of functioning as, a generator field strengthening circuit. When itis to be so used the switch B is closed before the switch A is closed, thus throwing the motor on the line before the resistor20 is cut in.. The cutting in of the resistor 20 after the motor has attained speed reduces the effective resistance in the generator shunt.

field circuit and thereby strengthens the generator shunt field.

It will be understood that I desire to com- '1. In a motor control system, the come 10. In combination with a generator cirada ted to be connected to the series motor fiel circuit,a motor commutating field cirl cuit comprising. an armature, a commutating field and a permanent resistor, switches connecting the commutating field circuit to the generator circuit and to the bleeder circuit, and a switch forconnecting the motor series field circuit to the bleeder circuit and the commutating motor field circuit so connected.

v 11. In a motor control system in combination with a generator and a circuit therefor,

including a generator shunt field winding and a resistance, of a motor having a series field winding connected with that side of said generator circuitwith which said generator resistance is connected, an armature connected to the other side of said generator, a generator field strengthening circuit connected with said generator resistance, and means for connecting said generator field strengthening circuit with that side of said 7 motor armature with which said motor series field winding is connected.

12. In a motorcontrol system, the combination with a generator and a circuit therefor including a generator shunt field winding, of a motor having a series field winding nected and having the other side thereof adapted to be connected to the motor circuit on that side of the motor armature with which the motor series field is connected, and operable means for connecting said variable resistor and the last mentioned resistor one after the other to said motor armature.

13. In a motor control system, the combination with a generator and a circuit therefor including a generator shunt field winding, of a motor having a series field winding connected to said generator circuit on one side of said shunt field winding and an armature connected to said generator circuit 011 the other side of said shunt field winding, a variable resistor adapted to be connected in series with said motor armature, a resistor having one side thereof connected to some point in the generator shunt field circuit on that side of said generator shunt field winding with which said motor series field is connected and having the other side thereof adapted to be connected to the motor circuit between the variable resistor and the motor said variable resistor with said motor arma- 14.- Ina motor control system, the combination with a generator and a circuit therefor, including an armature, a shunt field and a permanent resistor between said generator and said shunt field, of a motor series field having a circuit connected with that side of said generator circuit with which said resistor is connected, a motor armature and a circuit therefor connected with the other side of said generator circuit, means to bleed current from the generator circuit and by-pass it through the motor armature circuit and through said permanent resistor, whereby current is shunted around the generator shunt field for the purpose of reducing the field strength of the generator to reduce maximum in-rush current when starting the motor. In testimony whereof, I aflix my signature;

HENRY s. JACOBS.

Images