Foam proportioning system with solid state contactor
Embodiments of the invention provide a foam proportioning system powered by a battery, with the system including a pump, a pump motor, and a solid state contactor. The solid state contactor includes a battery terminal connected to the battery, a load terminal connected to the pump motor, and an enable switch. The enable switch selectively connects the battery terminal and the load terminal in order to form a power line carrying a current from the battery to the pump motor. A state of the enable switch is based on the current being drawn through the power line by the pump motor. The enable switch is closed in order for the solid state contactor to provide power to the pump motor when the current through the power line is between about zero amps and about 80 amps.
1. A foam proportioning system powered by a battery, the system comprising:
a pump with a pump motor; and
a solid state contactor including a single battery terminal connected to the battery, a single load terminal connected to the pump motor, and a non-load current carrying enable switch selectively connecting the single battery terminal in series with the single load terminal in order to form a power line carrying a positive load current from the battery to the pump motor;
selectively activating the enable switch based on the current drawn through the power line by the pump motor;
the enable switch being closed in order for the solid state contactor to provide power to the pump motor when the positive load current through the power line is between about zero amps and about 80 amps.
2. The system of claim 1 wherein the solid state contactor can withstand current through the power line of up to about 1200 amps for about 500 milli-seconds.
3. The system of claim 1 wherein the solid state contactor removes power from the pump motor if the pump motor attempts to draw greater than about 80 amps for longer than about 500 milli-seconds.
4. The system of claim 1 wherein the pump motor is a 24-volt direct current motor.
5. The system of claim 1 wherein the battery provides between about 10 volts to about 29 volts.
6. The system of claim 1 wherein the solid state contactor provides power to the pump motor when an input voltage from the battery is between about 9 volts and about 28 volts.
7. The system of claim 1 wherein the solid state contactor removes power from the pump motor when an input voltage from the battery is less than about 8 volts.
8. The system of claim 1 wherein the solid state contactor provides power within about 25 milli-seconds and can remove power within about 2 milli-seconds.
9. The system of claim 1 wherein at least one of the single battery terminal and the single load terminal is constructed of at least one of stainless steel and bronze.
10. The system of claim 1 wherein at least one of the single battery terminal and the single load terminal is covered by a rubber protective terminal boot.
11. The system of claim 1 wherein the solid state contactor includes a thermal transfer material on at least one side that is mounted to a metal mounting surface for heat dissipation.
12. The system of claim 1 wherein the enable switch is one of a ground-actuated toggle switch and a dry contact relay.
13. The system of claim 1 wherein the solid state contactor can operate in a temperature range of about negative 40 degrees Fahrenheit to about positive 160 degrees Fahrenheit.
14. The system of claim 1 wherein the solid state contactor draws up to about 15 milli-amps during operation of the pump motor.
15. The system of claim 1 wherein the solid state contactor draws an activation current of up to about 30 milli-amps.
16. The system of claim 1 wherein a resistance between the single load terminal and the single battery terminal is less than or equal to about 1 milli-ohm when power is provided to the pump motor.
17. The system of claim 1 wherein a resistance between the single load terminal and the single battery terminal is greater than or equal to about 250 kilo-ohms when power is removed from the pump motor.
18. The system of claim 1 and further comprising a capacitor connected to the pump motor; and wherein the solid state contactor gradually charges the capacitor when the pump motor is turned on in order to prevent arcing.
19. The system of claim 18 wherein the capacitor is about 82,000 micro-farads.
20. The system of claim 18 wherein the capacitor draws a larger input current for about 200 milli-seconds after the pump motor is started.
21. The system of claim 1 wherein the solid state contactor removes power from the pump motor within about 25 milli-seconds if the current is between about 80 amps and about 250 amps.
22. The system of claim 1 wherein the solid state contactor removes power from the pump motor within about 5 milli-seconds if the current is greater than about 250 amps.
23. The system of claim 1 wherein the single battery terminal of the solid state contactor is connected to a positive terminal on the battery.
24. The system of claim 1 wherein the solid state contactor carries only a positive load current between the battery and the single load terminal.
25. A proportioning system powered by a battery, the system comprising:
a pump with a pump motor to introduce a foamant into a fluid stream; and
a solid state contactor including a single battery terminal connected to a positive terminal on the battery, a single load terminal connected to the pump motor, and a non-load current carrying enable switch selectively connecting the single battery terminal in a series connection to the single load terminal in order to form a power line through the solid state contactor, the power line carrying a positive load current from the battery to the pump motor;
selectively activating the enable switch based on the current drawn through the power line by the pump motor;
the state of the enable switch being operable to be closed in order for the solid state contactor to provide power to the pump motor when the positive load current through the power line is between a predefined range.
26. A foam proportioning system powered by a battery, the system comprising:
a pump with a pump motor; and
a solid state contactor including a single battery terminal connected to the battery, a single load terminal connected to the pump motor, and a control input terminal for user connection of an input signal, the control input terminal connected to a non-load current carrying, user activatable enable switch to selectively activate and deactivate the solid state contactor;
the enable switch selectively activating the solid state contactor to connect the single battery terminal in series with the single load terminal in order to form a series connection through the solid state contactor to carry a current from the battery to the pump motor;
the enable switch being electrically connected to one of a positive terminal on the battery and a negative terminal on the battery to activate the solid state relay to form the series connection to carry the current from the battery to the pump motor only when the current through the series connection is between a predefined range.
27. The system of claim 26 wherein the predefined range is between about zero amps and about 80 amps.