US2342961A - Electric motor controller - Google Patents

Description

Feb. 29, 1944. I NEWMAN 7 2,342,961

ELECTRIC MOTOR CONTROLLER Filed July 16, 1942 .L1 Baal La R9 1 V 150 v 2E2 F X I i H {1M0- V V l 3A 2A MS L l HOIST LOWER I oFF 545:1 12345 W L i E l HM -0 l iil NIH: ]-I5 )7 ii'o oLii '5 l8 1 l l I K I iIIlI/Kllll? 1 j o: CON-FACTOR CLOSED 9: SPRING CLOSED es CONTROLLED BY 16R a) CONTROLLED BY VR Patented Feb. 29, 1944 ELECTRIC MOTOR CONTROLLER John M. Newman, Wauwatosa, Wis., assignor to I Cutler-Hammer, Inc.

Milwaukee, Wis., a cor, poration of Delaware Application July 16, 1942, Serial No. 451,152 9 Claims. (01. 172-152) This invention relates to improvements in controllers for motors in crane hoist and similar service.

In Patent No. 2,288,133, issued June 30, 1942, there is disclosed a controller for crane hoists, and the present invention while not limited thereto is especially applicable to such type of controller.

The controller of the aforementioned patent provides for operating a direct current motor as a series motor for hoisting and as a shunt motor for lowering and provides for dynamic braking of the motor under overhauling load conditions. Also it provides for high speed lowering at substantially the same speed whether the load is heavy and overhauling or whether the hook is empty. In most instances it is desirable to maintain power connections for the motor throughout lowering and said patented controller is designed to maintain such connections.

n the other hand, it has been found desirable in certain instances, as where the system employs a Diesel engine or the like as a prime mover, to prevent the motor when driven by its load from pumping back current to the line, and the present invention has among its objects to provide a controller having substantially all the advantages of the controller of said patent but which will afford protection against pumping back of current by the motor.

Another object is to effect the desired control with but slight modification of said patented control.

Another object is to utilize for controlling disconnection from the line in lowering a relay serving to control for uniform high speed lowering under the different load conditions hereinbefore mentioned.

Other objects and advantages of the invention will hereinafter appear.

The present invention because of ease of embodiment in the aforementioned earlier controller has been so illustrated in the accompanying drawing which will now be described, it being understood that the invention is susceptible of embodiment in other forms without departing from the scope of the appended claims.

In the drawing,

Figure 1 is a diagrammatic view which for simplicity of illustration omits numerous details and control circuits now known to the art, and

Fig. 2 is a chart showing the sequence in which the switches or contactors shown in Fig, 1 are to be operated.

Referring to Fig. 1 of the drawing it shows a motor M having an armature A and a field winding F to be connected to lines L L. in series relation for hoisting and in shunt relation for lowding. These and other connections for the motor are made by switcheswhich in type and number are the same as in the controller of the patent aforementioned, and as will be understood these switches are to be assumed to be operated by electroresponsive windings although in most instances the switches are here shown without windings for simplicity of illustration. In most instances the control of these switches is the same as in the controller of the patent aforementioned and in the drawing hereof such common circuits as well as the master switch contacts have for simplicity of illustration been omitted except where illustration has been made to clarify the modification here involved.

Switches M and H provide for connection of the motor armature and field winding in series to lines L and L through resistors R, R R, R and R in series for hoisting, resistor R being shunted throughout hoisting by switch I which is biased to closed position and switch 2DB being open instead of closed as shown. Resistors R R and R3 are adapted to be shunted progressively by switches 2A, 3A and A, respectively, these switches closing sequentially as shown by the chart Fig. 2 under the control of contacts (not shown) of master switch MS and certain of said switches preferably having a. definite time element incident to closure. Thereafter as indicated by saidchart, switches 5A and 6A may be closed to shunt resistors R and R preferably subject to control to render their closure sequential and each subject to a definite time element. Thus provision is made for acceleration and speed control in hoisting in accordance with earlierpractice, the indicated closure of switch IKO in the first and second hoisting positions being here neglected but later discussed.

Switches M, IKO and IDB, here neglecting switch 2DB and the circuit controlled thereby, provide for connection of the motor armature and field winding in parallel to lines L and for lowering. Switch IKO establishes a circuit from line L through resistor R to the motor M at a point between its armature and field winding. From the other side of the armature circuit extends to and through resistors R and R to and through the coil of a relay VR in parallel with resistor R to and through coil 0 of relay ICR and thence through switch IDB and switch M to line L. From the right hand terminal of brake coil B to and through resistors R, R and R and thence through switch IA and switch M to line L As indicated by the chart, Fig. 2, switches 2A; 3A, 4A, 5A and 6A are closed in the first lowering position and thus if switch lA remains closed the motor circuits are without resistance other than the resistor R common to the armature and field circuits and the fixed resistance R in the armature branch in'parallel with the winding of the relay VR. This is in accordance with earlier practice, as is also opening of switches 4A, 5A and 6A in the second lowering position and opening of switch 3A in the third lowering position, all as indicated by the chart Fig. 2, first to include in the armature circuit resistors R and R and in the field circuit resistor R and then to include in the field circuit resistor R Meanwhile switch IA remains closed for its operating winding is controlled by normally disengaged contacts 2I of the master switch MS, which contacts are not engaged until the master switch is moved to its fifth lowering position. As will be understood, the positions of the master switch which effect engagement of its contacts disengaged in oil position are indicated by circles and thus as there is but one circle in line with contacts 2i it will be understood that said contacts shown as disengaged will remain in that relation except in the fifth lowering position later to be discussed.

As in the controller of the patent aforementionedand as indicated by the chart Fig. 2, the switch 2DB closes only in the off position of the master switch. When closed the switch 2DB completes a dynamic braking loop extending from the left hand terminal of the motor armature A to and through switches 5A and 6A to and through the winding of relay VR and parallel resistance R' and thence to and through the winding of relay ICE and the contacts of switch IDB to the .right hand terminalof motor field winding F.

This connects the motor armature and field winding in series for dynamic braking with the brake coil B excluded from circuit. As in the earlier controller and as shown by the chart Fig. 2 the switches A and 0A are now subject to control by the relay VR for graduation of dynamic braking as the motor comes to rest.

Now considering the provisions departing from the earlier control and again considering control for lowering, the relay ICR has been given the dual function of controlling switch IA and controlling switch IKO. More specifically the relay ICR which as in the earlier control is closed in all lowering positions'pending overhauling of the motor opens whenever the motor overhauls, but it closed when the master switch MS is moved to final lowering position coacts therewith to energize switch IA to insert in the field branch of the motor, resistor R, to afford a high speed for an empty hook substantially the same as the lowering speed under heavy overhauling load conditions. Also in the control here provided the switch IE0 is placed under the control of relay ICE in the fourth and fifth lowering positions as indicated by the chart Fig. 2 whereby if whenthe motor tends to act as a generator with consequent response of relay ICR the switch IKO is caused to open to disconnect the motor from supply line L This protects the system against undesired pumping back of current.

This dual functioning of the relay ICE. is provided for in the following manner. The wind- 2,8&2,961

series with the motor armature in lowering and is subject to current reversals when the motor acts as a generator, whereas the winding 0 of said relay is subjected to only a unidirectional flow of current being connected across the line in series with the winding of under-voltage switch UV for energization continuously under normal conditions. Thus provision is made'for the aforedescribed action of relay ICR per se. The circuit for switch IA controllable by relay ICR extends from line L through contacts 2I of the master switch MS but only when in its last lowering position by conductor III to and through the winding 0 of switch IA by conductor II through auxiliary normally open contacts I2 of switch 6A by conductor I3 through the contacts of relay ICR to line L As shown there is a parallel circuit from conductor I3 through normally closed auxiliary contacts ll of switch 2K0 by conductor I5 to line U but this parallel circuit is interrupted in the fourth and fifth lowering positions because of energization of the switch 2K0 as shown by the chart Fig. 2, wherefore the switch IA is under the control of the relay ICR alone in the fifth lowering position. The circuit for switch IKO controllable as aforedescribed by the relay ICR extends from line L through the contacts 20 of the master switch MS in all lowering positions by conductor I6 through normally open auxiliary contacts H of switch M, by conductor I8 to and through the contacts of relay ICE. to line 1 Alternatively circuit may be traced from conductor I8 by conductor I3 through the normally closed contacts ll of the switch 2K0 to line L and thus as the switch 2K0 is not energized except in the fourth and fifth lowering positions its auxiliary contacts I4 render energization of the switch IKO independent of relay ICR. in the first three lowering positions but subject to control by said relay in the fourth and fifth lowering positions.

While the provisions just described prevent the relay ICR. from deenergizing the switch IKO to disconnect the motor from line L except in the fourth and fifth lowering positions it may in someinstances be desirable for power saving or for other reasons to have switch IKO under the control of relay ICR. in all lowering positions. Where this is desired it is only necessary to omit the auxiliary contacts it of switch 2K0.

With the modified control thus far discussed the speed torque characteristics are not as good as in the earllercontrol aforementioned, but substantially like characteristics have been found obtainable by providing as shown an armature shunt including a resistor R to by-pass from the motor field part of the armature current under overhauling load conditions. While the resistor R is shown as having permanent connection in the power circuit it is to be understood that it might have control means to make and interrupt its connection as desired, and that its location in circuit is susceptible of change. However, its .location as illustrated has been found advantageous especially in minimizing its effect in both lowering and hoisting positions other than in: 0 of relay ICE is connected at all times in hoisting positions.

What I claim as new and desire to secure by Letters Patent is:

1. In control for hoist motors, the combination with means selectively to establish power connections for hoisting or power and dynamic braking connections for lowering and to aflord speed control, of means to render substantially uniform under heavy and light loads a high lowering speed selectable by the first mentioned means and to effect through the medium of said first power connections at certain of the lowering' aasacer speeds when the load is overhauling, the second mentioned means comprising a relay which is subject to control by dynamic braking current and which renders said second mentioned means automatic in performing both aforemention 7 functions thereof.

3. In control for hoist motors, the combination with means selectively to establish power connections for hoisting or power and dynamic braking connections for lowering and to afford speed control, of means to render substantially uniform under heavy and light loads a high lowering speed selectable by the first mentioned means and to eflect through the medium of said first mentioned means interruption of lowering power connections at certain of the lowering speeds when the load is overhauling, the second mentioned means having for rendering the same automatic in performing both aforementioned functions thereof a relay with control windings connected in circuit in lowering to act diflerentially or cumulatively according to the weight of the load. 7

4. In control for hoist motors, the combination with means selectively to establish power connections for hoisting or power and dynamic 'bralring connections for lowering, said means aflording any one of a number of speeds in hoisting or lowering and having an electro-responsive switch through which it tends at all lowering speeds to maintain said lowering power connections, of a' relay to control said switch for action thereof to interrupt power connections at certain of the lowering speeds when the load is overhauling, said relay having a plurality of control windings one of which is subjected to a unidirectional fiow of current regardless of load conditions and another of which is traversed by current changing in direction of flow according to whether the load is light or overhauling.

5. In control for hoist motors, the combination with means selectively to establish power connections for hoisting or power and dynamic braking connections for lowering, said means affording any one of a number of'speeds in hoist- 1 ing or lowering and having an electro-respcnsive switch through which it tends at all lowering speeds to maintain said lowering power connections, of a relay to control said switch for action thereof to interrupt power connections at certain of the lowering speeds when the load is overhauling, said relay having a plurality of control windings one of which is subjected to a unidirectional flow of current regardless of load conditions and another of which is traversed by current changing in direction of fiow according to whether the load is light or overhauling, and means controlled by said relay and the first mentioned means jointly to afford high speed lowering at substantially the same rate whether the load is light or overhauling.

6. In combination a series hoist motor, means selectively to establish power connections for said motor for hoisting, with the armature and field winding of the motor in series, or power and dynamic braking connections for said motor for lowering, with the motor field shunting the armature, means to eil'ect through the medium of the first mentioned means during lowering at certain of the lowering speeds, interruption of power connections when the load is overhauling and a circuit to by-pass from the motor field winding some of the armature current for improved speed torque characteristics.

7. In control for hoist motors, the combination with means selectively to establish power connections for hoisting or power connections for lowering, said means including a master switch having diflerent positions for selection of speeds in both hoisting and lowering and said means tending to maintain power connections throughout lowering regardless of the lowering position occupied by said master switch, and means eiIective when said master switch is in certain of its lowering positions to cause the first mentioned means to interrupt power connections under overhauling load conditions, but ineilective in other of the lowering positions of said master switch.

8. In a hoist system having as a prime mover a Diesel engine and having a hoist motor which under overhauling loads tends to pump back current with undesirable eflects on such prime mdver, the combination with motor controlling means which establish power connections for lowering and which afford a plurality of lowering speeds and tend to maintain power connections regardless of overhauling load conditions, of means effective under overhauling load conditions at least at certain of the lowering speeds to cause the first mentioned means to interrupt power connections, the first mentioned means including means which at certain of the lowering speeds renders the second mentioned means ineffective to function as stated.

9. In a hoist system having as a prime mover a Diesel engine and having a hoist motor which under overhauling loads tends to pump back current with undesirable effects on such prime mover, the combination with motor controlling means which establish power connections for lowering and which afford a plurality of lowering speeds and tend to maintain power connections regardless of overhauling load conditions, of means'eflective under overhauling load conditions at least at certain of the lowering speeds to cause the first mentioned means k; interrupt power connections, and means which together with the second mentioned means provides means affording high speed lowering at substantially the same rate whether the load is light or overhauling.

JOHN M.

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