CA1262184A

CA1262184A - Load control apparatus

Info

Publication number: CA1262184A
Application number: CA000516623A
Authority: CA
Inventors: Carl S. Newman
Original assignee: AEG Westinghouse Transportation Systems Inc
Current assignee: Bombardier Transportation Holdings USA Inc
Priority date: 1985-08-23
Filing date: 1986-08-22
Publication date: 1989-10-03
Also published as: GB2179498A; GB8619773D0; AU6115186A; GB2179498B; AU604642B2

Abstract

ABSTRACT OF THE DISCLOSURE

Load control switch apparatus for a load circuit determines the energization and protection of that load circuit, and includes two movable contacts, with the load circuit energization contact operating at a slower speed than the load circuit protection contact. A first reset apparatus is provided to reset the position of the load circuit protection contact, and then a second reset appara-tus is provided to reset the position of the load circuit energization contact after the load circuit protection contact has been reset.

Description

1 52,835 LO~D CONTROL APPARATUS

BACKGROUND OF THE INVENTION
It is known in the prior art to provide a switch-ing apparatus for controlling and protecting the operation ~ of a load, and including an electromagnetic contactor section for slow acting line switch operation in combina-tion with a protection apparatus responsive to an overload current condition for fast acting operation such that a movable contact is positioned in relation to a stationary contact, as disclosed in U.S. Patent 4,042,895 of Wafer et al.
SUMMARY OF THE INVENTION
A load control switch for load circuit control : and protection is provided with two movable contacts, including one fast actin~ contact operating in response to a predetermined overload current condition and tha other slow acting contact operating in response to open and close switch commands ~rom an operator or associated control system.
The invention includes the control of the spaclng between the two movable contacts when the fast acting contact is in the open positio~. The invention also includes providing relative rates of motion between the faster and slower acting contacts with a predetermined acceleration relationship such as in a ratio of about 2:1.

R~i,jJ

2 52,835 BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a prior art load control switch arrangement;
Figure 2 shows a prior art current control arrangement for a load, such as for the propulsion motors of a mass transit vehicle;
Figure 3 shows a prior art combination line switch and overload current protection apparatus suitable for the protection of a load, such as for the propulsion motor of a mass transit vehicle;
Figure 4 shows a prior art control circuit for the magnetic control valve providing the slow operation of a line switch;
Figure S shows the operation of the control valve to control an air cylinder coupled with the movable contact of a line switch;
Figure 6 shows the line switch and overload current protection apparatus of the present invention;
Figure 7 illustrates the open position of the right contact shown in Figure 6;
Figure 8 illustrates an ~nd view of the motor : current sensing solenoid shown :Ln Eigure 6; and Figure 9 shows the reset operation for the left contact shown in Figure 6.
~5 DESCRIPTION OF A PREFERRED EMBODIMENT
In Figure 1 there is shown a prior art load control switch apparatus including a power source 10 coupled through a line switch 12 and a current regulator 14, such as the well known chopper apparatus disclosed in U.S. Patent 4,284,930 of T. C. Matty, ~or energizing a load such as a propulsion motor circuit 16.
In Fiyure 2 there i~ shown a prior art power control arrangement for a load, such as for the propulsion motors of a mass transit vehicle. When the line switch 12

3$ is closed by àn automatic control operation or an operator, the filter capacitor 18 in conjunction with the line reac~or 20 and operates to keep the voltage ripple provided 3 52,835 by the current regulating chopper 14 away from the power source 10. When the motor current is re~uested by an operator or an associated control system, the main chopper 14 operates to pulse width modulate the voltage or. the filter capacitor 18 to establish the average current supplied through the motor reactor 22 to the motor circuit 16, including a load 24 such as a vehicle propulsion motor.
This average current determines the tractive effort provid-ed by the load motors 24~ The free wheeling diode ~6 provides a path for the current generated by the collapsing motor flux when the chopper 14 is turned off.
In Figure 3 there is shown a prior art combina-tion load control system energization switch and overload current protection apparatus, which can be operable as the lS line switch 1~ shown in Figure 2, and includes a movable contact 30 connected with an air cylinder position control assembly 32 for moving the contact 30 into the position shown in Figure 3 in relation to a stationary contact 34, to complete the electrical circuit between the power source 10 and the load 24. The motor current flows through a motor current sansing coil 36, of an overload current protection apparatus 38, which provides a magnetic field to pull in an armature 40 counterclockwise about pivot 47 to operate a cam 42 for mo~ing a contact 44 in relation to a stationary contact 46. The separation of the contacts 44 and 46 breaks a circuit including a control voltage source 52 operative with the control valve coil 48 of the control valve 50 operative with the air cylinder assembly 32.
When the control valve coil 48 for the control valve 50 is deenergi ed, the control valve 50 opens to exhaust the air chamber 58 operative with the piston 60 coupled throu~h the arm 62 and the arm 70 to move the contact 30. A return spring 57 moves the piston 60 down-ward to separate th~ contacts 30 and 34 when the air chamber 58 is exhausted.
When the overload current sensing apparatus 38 senses a motor current graater than a predetermined

4 52,835 magnitude, the coil 36 pulls the armature 40 to the left about pivot 47 and the connecting link 68 operates to rotate the arm 70 away from the stop 71 and about the pivot 72 to separate the movable contact 30 away from the sta-tionary contact 34. As the armature 40 moves left the cam42 permits the lea:E spring 74 to move the contact 44 away from the stationary contact 46. This deenergizes the control valve coil 48 to permit the valve 50 to move to the normally open position.
lC W~len the operator or an associated automatic control system desires to close the contacts 30 and 34 for energizing the load 24, the control switch 54 can ~e closed to energize the control valve coil 48 through the contacts 44 and 46 of the overcurrent protection mechanism 38. This moves the valve member 56 of control valve 50 to the left as shown in Figure 5 to introduce pressurized air from source 64 through passage 59 into the air chamber 58 for moving the piston 60 to move contact 30 upward and against the stationary contact 34. As the piston 60 moves upward, first the contact 30 is positioned against the contact 34 and then the contact pressure spring 65 is compressed to allow the contact arm 70 to rotate about the pivot 72 as the pivot 72 moves upward with the piston 60 to the end of the travel of the piston 60 against the stop 63 within the cylinder 65.
When the armature 40 is rotated counterclockwise about the pivot 47, a latch 43 is pushed by a compression spring 49 to operate with stop 45 for holding the armature 40 in this latched position. When it is desired to reset the control apparatus shown in Figure 3, a reset solenoid 41 is energized with the control voltage to raise the latch 43 above the stop 45, such that the armature 40 is released to move clockwise about the pivot 47 into the position as shown in Figurs 3. A tension spring 51 provides the force to move the un~atched armature 40 into the position shown in Figure 3;

52,835 Figure 4 shows a suitable prior art control circuit for the control valve coil 48 coupled with the air cylinder assembly 32 to provide the line switch function of the line switch 12. The control voltage source 52 is coupled through a control switch 54 and the overl~ad current protection apparatus 38 including contacts 44 and 46 for determining the energization of the control valve coil 48 operative through the air cylinder assembly 32 with the line switch 12.
10In Figure 5 there is provided a schematic drawing of the control valve member 56 provided within the control valve 50 and coupled with the magnetic control valve coil 48. The control valve 56 is normally positioned as shown in Figure 5. When the coil 48 is energized through the 15closed contacts 46 and 44, the control valve 56 moves to the le~t such that the pressurized air source 64 is con-nected to the air chamber 58 through passage 59 for moving the piston 60 upward in a direction to position the movable contact 30 in connection with the stationary contact 34.
20If the operator desires to deenergize the load 24, the control switch 54 is opened to deenergize the control valve coil 48 to move the valve 56 into its posi-tion shown in Figure S for moving the piston 60 downward by the effort of the return spring 57, which movement will 25open the contacts 30 and 34 by moving the contact 30 away from the contact 34 after the ~pring 65 rotates the arm 70 against ~top 71.
In Figure 6 there is shown the control apparatus of the present invention for providing the operation of a line switch and an overload current protection apparatus.
A first movable contact 80 is carried by a contact arm 82 that rotates about a support pivot 84. A motor current sensing solenoid 85 includes an armature 86 having a non-magnetic hooX 99 coupled through a link 88 to control the rotation o a latch member 90 about a support pivot 92.
A conductor 94 carrying load current passes through the 6 52,835 solenoid 85 and includes a flexible section 87 to allow the contact arm 82 to move about the pivot 84.
As shown in Fi~ure 8, an arm 98 is coupled between the solenoid armature 86 and a tension spring 100 which operates with an adjustable fastener 102 for provid-ing desired adjustment of the tension of the spring 100.
The arm ~8 coupled with the armature 86 moves about a support pivot 104 suc~ that the armature 86 is held in a raised position until an overload current through the conductor 94 creates magnetic lines of force in the air gap 87 between solenoid 85 and armature 86 to pull the arma-ture 86 down against the force of the spring 100. The hook 99 is connected to move with the armature 86 and includes a notch 101 which engages an opening in link 88.
When the armature 86 moves down, the link 88 moves down to raise the right end of the latch 90 about the pivot 92 such that the keeper 106 is unlocked and the compression spring 108 operates with the link 110, pivotal-ly connected to the arm 82 at pivot 111, to pull the contact arm 82 to the left about the pivot 84 to move the left contact B0 away rom the ri~ht contact 112. A stop 109 is provided to limit the travel of link 110 and counterclocXwise movement of the arm 82, and to minimize bouncing of the contact 80.
The right contact 112 is carried by a contact holder 118 which pivots relative to contact arm 114 at contact holder pivot 120. A contact pressure compression spring 122 operates to hold the right contact 112 against the locked position of the left contact 80.
In the closed position~of the contacts 80 and 112 as shown in Figure 6, the contact holder 118 is moved away from the provided stop 124 by the force supplied through the contact arm 114 by the control voltage solenoid 126.
The solenoid 126 can function substantially the same as the air cylinder assembly 32 shown in Figure 3, such that control switch 54 energizes the solanoid 126 from a control voltage source 52 to pivot the contact arm 114 counter-18f~
7 52,835 clockwise about the support pivot 116 and against the force of tension spring 127~
In Figure 7 there is shown the open position of the right contact 112~ with the solenoid 126 deenergized to permit the tension spring 127 to move the contact arm 114 clockwise about the pivot 116 to the right, such that the contact holder 118 separates the right contact 112 from the left contact 80. The compression spring 122 moves the contact holder 118 about the pivot 120 and against the stop 124, which is fixed in position relative to the arm 114.
The solenoid 126 operates to move the contact arm 114 about the pivot 116 to move the contact holder 118 and the contact 112 to open or close the gap between the contacts 80 and 112 as desired. The contact 112 may only be closed after the left contact 80 is latched.
In Figure 8 there is shown an end view~ taken for Section VIII-VIII shown in Figure 6, of the load current sensing solenoid 85, with the armature 86 movable about a hinge 104 and pulled into a raised position by the arm 98 operative with the tension spring 100 as adjusted by the fastener 102. When an overload current above a predeter-mined amount passes through the conductor 94, the armature 86 is pulled down by th~ resulting magnetic lines of force such that the link 88 is pulled down and rotates the latch 90 about the pivot 92 for releasing the keeper 106 to permit the arm 82 to move counterclockwise about pivot 84 for providing a non conductive gap between the contacts 80 and 112.
When solenoid 85 senses a current overload condition, the left contact 80 is released and responds to the force selected for the spring 108 to provide an accel-eration rate of the left contact 80 of about 185 G's which would provide a fully open and non-conductive gap between the contacts 80 and 112 in about 4 milliseconds. The acceleration rate of the right contact 112 is determined by the force selected for the spring 122 to provide an accel-eration rate about 85 G's, which is considerably less than 1~ 34 8 52,835 the provided acceleration rate of the left contact 80.
Thusly, the right contact 112 moves too slowly to follow an opening movement by the left contact 80. This establishes the relative rates of acceleration to be in a desired ratio of about 2 to l. One G is the well-known acceleration provided by gravity. In this way a relative motion is provided ~etween the contacts 80 and 112, such that the contact 80 moves away from the contact 112 faster than the contact 112 is able to move, such that the contact 112 is not able to follow 80 so a desired non-conducting circuit gap is provided substantially as soon as left contact 80 starts to move.
In Figure 9 there is shown the reset operation for the left contact 80, which is provided before the solenoid 126 i energized to move the right contact 112 into conductive position against the previously latched left contact 80.
When it is desired to reset the latched position of the left contact 80, with the right contact 112 in open position to avoid a possible fault condition otherwise, a reset motor 140 is energized through a reset control switch 141 and limit switch 162 by the control voltage source 52 to move the contact arm 82 clockwise about pivot 84. A
reset lever 142 moves clockwise about pivot 84 and includes an actuator arm 144 and a first scotch yoke 146. There is engaged with the yoke 146 a first arm 148 having a pin 150 and coupled with a rotatable shaft 152. At the other end of the shaft 152 is a second arm 154 including a second yoke 156, which operates with an eccentrically mounted pin 158 carried by a disc 160 driven by the reset motor 140.
At the home position o~ the disc 160 the actuator arm 144 is away from the connection pin lll coupled with the arm 82, which pin lll extends out of the plane of the drawing or cooperation with the actuator arm 144. When the reset 3S motor 140 is energized, the disc 160 rotates to cause the pin 158 to slide within the second yoke 156 to cause the sha~t 152 to rotate for providing curvilinear movement of 9 52,835 the pin 150. The shaft 152 rotates about its axis in suitable bearings. At the home position of the reset motor 140 the second arm 154 is at 1:he extreme clockwise posi-tion, as is the first arm 148, and the reset lever 142 is S at the extreme counterclockwise position such that the actuator arm 144 does not touch the pivot pin 111 when the contact 80 moves into the open position.
When the reset motor 140 i~ energized, the ~irst arm 148 turns counterclockwise and the actuator arm 144 engages the pivot pin 111. Continued operation of the motor 140 moves the arm 82 until the latch 90 engages the keeper 106 under the influence of tension spring 91, and there is a small overtravel until the eccentric pin 158 reaches top dead center relative to the second yoXe 156.
Continued opera-tion of the motor 140 causas the actuator arm 144 to move away from the contact arm 82 and the keeper 106 holds the latch 90. A limit switch 162 operates with the disc 160 to control the home and deenergized position of the reset motor 140 and a limit switch 164 energizes the ~olenoid 126 to cause the right contact 112 to close. The disc operative with the left contact 80 includes two cams, 166 and 168, which are relatively displaced in reference to the plane of drawing, such that cam 166 operates the limit switch 162 which is closed except when the disc i5 in the 2S home position and that switch 162 controls the energization of the reset motor 140 to provide a single revol~tion o the motor operation. Cam 168 operates the limit switch 164 which subsequently operates the solenoid 126 so the contact 8p has to be in a latched position and the reset motor in the home position before the contact 112 ~s closed against the contact 80, As shown in Figure 6, the limit switch 164 operative with the reset disc 160 is coupled within the control voltage circuit for the control voltage solenoid 126 to permit operation of the solenoid 1~6 only when the reset disc 160 is in its home or rest position. The limit switch 165 is operative with the link 110 to respond .

52,835 to the opening of the contact 80 for deenergizing the solenoid 126 to move the contact 112 into its open position.

, ~

Claims

CLAIMS:

1. In control switch apparatus operative with a source of control voltage and responsive to the current of a load, the combination of:
a first movable contact and a second movable contact means for supporting said first and second contacts for engage-ment with each other to complete a circuit for load current flow;
first control means connected with the first contact support means and responsive to said control voltage to move said first contact between open and closed positions for line switching operations, and second control means connected with the second con-tact support means and responsive to said load current to move said second contact from closed position to open position on current overload.

2. The control switch apparatus of claim 1, with said second contact being movable at a first acceleration in response to a predetermined overload current condition, and with said first contact being movable at a second acceleration in response to an input control voltage signal, such that said first acceleration is greater than said second acceler-ation.

3. The control switch apparatus of claim 1, with one of the first and second contacts including reset control apparatus for determining a reset position for said one contact, and with the other of the first and second contacts being positioned to engage said one contact after said one con-tact has been reset to said reset position.

4. The control switch appratus of claim 2, with said second contact being movable with an acceleration at least twice the movement acceleration of said first contact.

5. The control switch apparatus of claim 1, with the second contact including first position control means for establishing a reset position for the second control means in response to said control voltage, and with the first contact including second position control means for providing engagement of the first and second contact means after the second contact means reset position has been established.

6. The control switch apparatus of claim 1, including third control means coupled with the first contact for establishing the first contact in closed position, and fourth control means coupled with the second contact for establishing the second contact means in closed position.

7. In control switch appratus operative with a control voltage and responsive to a load current, the combin-ation of a first contact member movable between a conductive position and a non-conductive position, a second contact member engageable with the first contact member to control said load current and movable between a conductive position and a non-conductive position, first means coupled with the first contact member and responsive to the control voltage to determine the conduct-ive position of the first contact member;
second means coupled with the second contact member and responsive to the control voltage to determine the conduct-ive position of the second contact member;
said first contact member being movable to said non-conductive position in response to a predetermined over-load current, and said second contact member being movable to said non-conductive position in response to said control voltage.

8. The control switch apparatus of claim 7, with the first contact member being movable at a first acceleration to said non- conductive position in response to a predetermined over-load current, and with the second contact member being movable at a second acceleration less than the first acceleration to said non-conductive position in response to said control voltage.