US2008845A - Automatic starter - Google Patents

Description

y 1935. H. L. VAN VALKENBURG 2,008,845

AUTOMATIC STARTER Filed Aug. 23, 1933 2 Sheets-Sheet l INVENTOR HEfMD/i 1:

y 1935. H. L. VAN VALKENBl JRG AUTOMATI C STARTER Filed Aug. 23, 1933 2 Sheets-Sheet 2 INVENTO ATTORNEY Patented July 23, 1935 UNITED' STATES 2,008,845 surom'nc STARTER Hermon L. Van Valkenburg, Wauwatosa, Wis., assignor to Square DCompany, Detroit, Mich.

Application August 23, 1933, Serial No. 686,396 7 Claims. (Cl. 172-279) This invention relates to .condenser type motors.

In single phase condenser type motors, it is desirable to cut out the starting winding after. the motor has come up to speed and to thereafter have the motor operate as a simple, single phase motor.

Objects of this invention are to provide a novel form of automatic starter particularly applicable to condenser type motors, in which a very simple construction is employed whereby a time delay is secured, such delay automatically adjusting it- I self to the particular load that the motor is carrying.

Further objects are to provide a novel combination of condenser type, single phase motor and automatic starter, in which a thermal element is employed and responds to the current in the starting winding of the motor, so that, after the current in such winding rises to a predetermined value and has been maintained at approximately this value for a certain interval, the thermal element connects a contactor or similar device, so that the contactor will cut out the starting winding and will also hold itself closed and cut out the thermal element.

Further objects are to provide a combined automatic and manual control system for a single phase condenser type motor in which a contactor is provided and is controlled by a start button and by a stop button, the contactor in turn controlling the connecting of the motor and the automatic starter to the single phase line, and in which the automatic starter disconnects the starting winding after the motor has approximately come up to speed and particularly after the current in the condenser starting circuit has risen to approximately a certain value and has persisted at this value for a certain length of time, and in which the motor may be started or stopped by the start and stop buttons. I

An embodiment of the invention is shown in the accompanying drawings, in which:

Figure 1 is a ditic view of the system.

Figure 2 is a plan view of the automatic starter.

Figure 3 is a sectional view on the line H of Figure 2.

Figure 4 is a chart showing two curves, one of which indicates the current in the starting winding when the motor is lightly loaded, and the other of which indicates the current in the starting winding when the motor is more heavfly loaded, both curves being platted against time in seconds.

automatic starters for ing contacts for Figure 5 is a fragmentary face view of the holdthe contactor of the automatic starter.

Referring to Figure 1, it will be seen that a 5 condenser type motor has been indicated generally by the reference character I and is provided with a running winding 2, or main winding, and

a starting winding 3. A main contactor 4 is provided and has three contact arms, 5, 8, and l, 10 operated by the holding coil 8 in the usual manner. The stationary contact 9 is connected to the main l2 and the contacts l0 and ii are connected to the main i3. The contactor is provided with holding means it, which bridge across the 35 contacts of the starting button l5 and completes the circuit of the holding coil 8. The circuit of the holding coil, it being noted, extends from the contact 9 through the contacts of the stop button l6 and back to the contact ll. Obviously, if the 20 starting button I5 is depressed, such button being biased towards open position, the holding coil circuit will normally be closed and the contactor will thus close. Thereafter the holding coil cir- 5 cuit is automatically maintained closed by the contactor until the stop button i6 is depressed, such stop button being biased towards closed position. I

The main winding 2 of the motor is directly connected to the movable contacts 5 and 6 of the contactor. The starting winding 3 is connected to the movable contact 5 of the contactor at one side, and atthe other side is connected to a condenser ll. The condenser-is connected through 35 the automatic starter hereinafter described to the movable contact I of the contactor.

The automatic starter is shown diagrammatically in Figure 1 and is carried by a panel or base i 8. It is provided with an armature H! which is held in a retracted position by the spring 20 until the magnet coil 2| is energized. Further, it will be seen that a movable contact 22 is biased towards closed position and engages its stationary contacts 23 and 24 until the magnet coil 2| is 45 energized. When the magnet coil 2i is energized, it draws its armature IS inwardly and an insulating post or finger 25 engages the movable contact 22 and moves such contact away from its stationary contacts. 50

It will be seen that one side of the condenser I1, is connected to the stationary contact 23, and

that the stationary contact 2 is connected to one of the arms of a bi-metallic thermal element 25 provided with a movable contact 21 adapted ber 33 secured to to engage a stationary contact 28 when such element is heated to a predetermined temperature. A conductor connects the thermal element 2% to -the movable element l of the main contactor, and thus it will be seen that the current in the starting circuit of the condenser motor passes-through the thermal element 25 and heats the element, thereby causing contact 2'5 to engage contact 28.

When the contacts ment, it is clear that the circuit of the holding coil 2! of the automatic starter is closed, and consequently the armature I9 is drawn inwardly and thestarting winding circuit is opened. The contactor of the automatic starter is provided with a movable contact 29, which acts as a holding member to maintain the circuit of the magnet 2i closed after the armature l9 has once moved inwardly. This movable contact 29 is adapted to engage the stationary contacts 30 and Si and thus close the circuit of the operating magnet 2t of the starter contactor independently of the thermal element, so that when such thermal element subsequently cools and the contact 2'? moves away from the contact 28, the automatic starter will still remain closed.

Referring to Figures 2 and 3, it will be seen that the automatic starter is carried by the base it, previously mentioned, which may be provided with inwardly turned flanges 32 and is adapted to befastened against the wall with the base it vertical, as is obvious from Figures 2 and 3. This starter is provided with an insulating memthe base and provided with a rectangular cavity 3 5, within which the movable contact 22 is loosely ositioned, such contact being spring urged outwardly, as indicated at 35. The stationary contacts 23 and 2A are carried by overhanging clips 35, which are secured in place by means of screws 3i, such screws projecting upwardly and receiving the nuts 38. The insulating block 33 thus provides a housing for the movable contact 22.

A second block of insulating material is indicated by the reference character 39 in Figures 2 and 3 and carries terminal members iii to which the arms of thethermal element 255 are secured. This thermal element is- U-shaped, as may be seen from Figure 2, and is bi-rnetallic and is designed to warp or bend upwardly when heated. The movable contact 2i, see Figure 3, carried by such member (26), is adapted to engage a stationary contact 28 which is carried by an adjustable screw il threaded through the clip 12 and locked in place by the lock nut 33. This arm is connected to the stationary contact all, as may be seen from Figure 2. The clip 52 may be integral with or separate from the clip d2, which carries the stationary contact 3Q. It is shown as forming a unitary portion with the clip d2. The stationary contact 3t is carried by a short clip it, see Figure 2, and the members i l and Q2 are mounted in slots betweenraised portions 35%, and t? formed integrally with the insulating block 39.

The armature of the starter contactor indicated generally at H3 in Figures 1, 2, and 3, is provided with a projecting, insulating strip or arm 53, see particularly Figure 3. This insulating arm carries the movable contact member 251. As shown in Figures 5 and 6, the movable contact member 29 is provided with a central tongue 69 and with two outer tongues 59, which carry the actual contactpoints which engage the stationary contacts 30 and 3|. The center tongue 2'! and 28 are in engageence character 53 aooasas 69 is riveted'or otherwise secured to the insulating arm 68 and is bowed inwardly slightly with respect to the outer arms 50, as is most clearly shown in Figure 6.

In Figure 6 it will be seen that the contacts have been shown open, and it is apparent that when the contacts close, a scraping motion is produced, the springy movable contact ,member 29 yielding during this closing motion.

From actual tests conducted with this device, it has been found that the automatic starter opens the starting circuit or a lightly loaded condenser type of motor quicker than with a more heavily loaded motor.

The curves shown in Figure 4, indicated at A and B, are respectively the current curves in the starting winding of a two-horsepower, 220-volt condenser type motor, such curves being plotted against time in seconds. It will be seen from the curve A, which corresponds to the lightly loaded motor, that the current firstdrops and thereafter rises to a substantially constant value, as shown by that portion of the curve A indicated by the reference character 5i. As a matter of actual fact, at the knee of the curve, as indicated at 52, the motor is almost up to full speed.

The curve B shows the condition with the same setting of the starter for the same motor, but more heavily loaded. The current in the starting winding also drops during starting and thereafter rises to somewhere near the value of the curve A, at which cut-off occurs. However, as a matter of actual fact, the starter winding circuit opened at the point indicated by the referfor the curve A, and at the point 54 for the curve B. There is a certain amount of heat that had to be generated within the thermal element before it will function to close its contacts, the amount of heat, and consequently the length of time, depending upon the setting of the screw ll, see Figure 3. Advantage is taken or" this fact, as is obvious from an inspection of the curves A and B, so that a delayed action is obtained and the starting winding circuit is not opened until the current in the starting winding has reached an approximately predetermined value or has remained at somewhere near this value for an interval of time sufficient to cause the operation of the thermal element.

It will be seen that there is a direct cooperation 7 motor requires a certain interval of time during which the starting winding is eiiective and this interval of time is just sufiicient with this starter to cause the automatic operation of the starter. This interval is longer for a heavily loaded motor, as shown by curve B, than for a more lightly loaded motor as shown by curve A.

It will be seen that a very simple type of automatic starter for condenser motors has been provided by this invention which secures a delay corresponding to the loading of the motor, such delay being produced by the action of the thermal element, as hereinbefore described.

It will be seen further that the device cooperates in a novel manner with the condenser type motor due to the peculiar type of characteristics of the condenser motor, as shown by the curves A and B, and due to the action of the thermal element of the automatic starter.

This device has been used in actual installations and has functioned in a regular predetermined way under the various conditions of loadmg of the motor in a wholly satisfactory manner.

Although this invention has been described in considerable detail it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

I claim:

1. A starter for an electric motor having a main winding and a starting winding, said starter comprising a contactor for opening the circuit of the starting winding, said contactor being permanently biased towards closed position, a thermal element responsive to current in the starting winding circuit for controlling -said contactor,

and holding means for said contactor effective after said thermal element has operated.

2. A starter for a motor having a main winding and a starting winding, said starter comprising a contactor permanently biased towards closed position for opening the circuit of the starting winding, a thermal element responsive to current in the starting winding circuit controlling said contactor, and holding means for said contactor efiective after said thermal element has operated.

3. A starter for a motor having a main winding and a starting winding, said starter comprising an electromagnetic contactor biased towards closed position for opening the circuit of said starting winding, a thermal element responsive to current in the circuit of said starting winding 1 for controlling said contactor, and electrical holding means operated by said contactor for maintaining said contactor energized after said contactor has operated.

4. A starter for a motor having a main wind- .thermal means for controlling said electromagnetic means and adapted to be connected in the circuit of the starting winding, and. holding means for said electromagnetic means, said holding means being actuated by said electromagnetic means.

6. The combination of a motor having a main winding and a starting winding, a condenser connected to said starting winding, 2. bi-metallic thermal element operatively connected in the circuit of said starting winding, and an electromagnetic contactor for opening the circuit of said .starting winding, said contactor being controlled by said thermal element.

'7. An automatic starter for a motor having a main winding and a starting winding, said automatic starter comprising electromagnetic means for opening the circuit of the starting winding,

and a bi-metallic U-shaped thermal element adapted to be operatively connected in the circuit of said starting winding, said electromagnetic means being controlled by said thermal element.

HERMON L. VAN VALKENBURG.

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