Variable speed electrical motor with separate start windings and without centrifugal switch

Abstract

A variable speed electrical motor has windings and a rotor disposed within a motor housing. The motor is capable of operating at one of a plurality of discrete operating speeds. The electrical circuitry for each speed includes both a start winding for only that speed and a start capacitor for only that speed. In an optional embodiment, a switch for varying the speed of the rotor is disposed at a location external of the motor housing. The variable speed electric motor is ideal for use in a water recreational combination, such as a spa, hot tub or recirculating bath tub.

Description

FIELD OF THE INVENTION

[0001] This invention relates generally to electrical motors and, more specifically, to variable speed motors.

BACKGROUND OF THE INVENTION

[0002] Variable speed electrical motors are very popular for a wide range of uses. Typically, the switch mechanism which provides the motor with the capability of switching between two or more speeds is disposed on the rotating rotor portion of the motor, within the motor housing. Such switch mechanisms necessarily rotate as the rotor rotates. To connect the rotating switch to control wiring, some sort of brush and ring configuration must be provided.

[0003] One problem with such variable speed electrical motors is that the switching mechanism frequently fails. Also, the brush and ring configuration is prone to failure. In both cases, repair of the motor is awkward, time-consuming and expensive.

[0004] Another problem with such variable speed electrical motors arises when the user attempts to change the speed of the motor to a faster setting. With conventional variable speed motors, this action results in a momentary large increase in power consumption in the motor as the motor attempts to overcome inertial forces and ramp up the rotation of the rotor to the faster speed in a very short period of time. Such sudden increase in power consumption causes a large “spike” of required amperage to the windings and frequently trips out one of the thermal protectors on the motor. This results in a frustrating shutting down of the motor.

[0005] Accordingly, there is a need for a variable speed electrical motor which avoids this problem in the prior art.

SUMMARY OF THE INVENTION

[0006] The invention satisfies this need. In one embodiment of the invention, the invention is a variable speed electrical motor capable of operating at one of a plurality of discrete operating speeds. In the invention, the electrical circuitry for each speed includes both a start winding for only that speed and a start capacitor for only that speed.

[0007] In another embodiment of the invention, the invention comprises the variable speed electrical motor described above in combination with a switch for varying the speed of the motor, wherein the switch is disposed external of the motor housing.

DESCRIPTION OF THE DRAWINGS

[0008] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description, appended claims and accompanying drawings where:

[0009] FIG. 1 is an isometric view of an electrical motor combination having features of the invention;

[0010] FIG. 2 is a side view of a water recreational combination employing the electrical motor combination illustrated in FIG. 1;

[0011] FIG. 3 is an electrical circuit diagram of a variable speed electrical motor having features of the invention; and

[0012] FIG. 4 is a electrical circuit diagram for a variable speed motor of the prior art.

DETAILED DESCRIPTION

[0013] The following discussion describes in detail one embodiment of the invention and several variations of that embodiment. This discussion should not be construed, however, as limiting the invention to those particular embodiments. Practitioners skilled in the art will recognize numerous other embodiments as well.

[0014] The invention is an electrical motor combination 10 comprising a variable speed electrical AC induction motor 12 and a switch 14 for varying the speed of the motor 12.

[0015] The electrical motor 12 has windings and a rotor (not shown) disposed within a motor housing 16. Contrary to electrical AC induction motors of the prior art, the electrical motor 12 of the invention 10 has no speed-varying switch disposed within the motor housing 16. The switch 14 for varying the speed of the motor 12 is disposed external of the motor housing 16. The switch 14 is typically disposed within a separate switch box 18.

[0016] The electrical motor combination of the invention 10 is ideal for use in a water recreational combination 20 such as a spa, hot tub or recirculation bath tub. Such a water recreational combination 20 is described in co-pending U.S. patent application Ser. No. ______, filed Mar. 14, 2002, entitled ADJUSTABLE WATER THERAPY COMBINATION, the entire contents of which are incorporated herein by this reference.

[0017] FIG. 2 illustrates a typical portable spa 20 having a water basin 22 with side walls 24. Water is circulated from the bottom of the water basin 22 through water circulation lines 25, a centrifugal water pump 26 and back to the water basin 22, typically via water injection jets (not shown). The variable speed AC induction motor 12 is used to drive the water pump 26 so that water entering the water basin 22 via the water injection jets can be varied with respect to intensity and pulse characteristics. Speed control of the electrical motor 12 is accomplished by the switch 14 which is disposed within a switch box 18 external of the electrical motor 12. Main line operating power is wired to the switch box 18 via main power wires 28. Electrical motor power is provided from the switch box 18 to the electrical motor 12 via electrical motor input wires 30. The switch 14 within the switch box 18 controls the amount of main line power to the electrical motor 12. Control of the switch 14 can be made via a control panel (not shown) which is operably attached to the switch 14 within the switch box 18 by control wires 32. As illustrated in FIG. 2, the pump 26, water circulation lines 25, electrical motor 12 and switch box 18 can be conveniently located within a spa surround 34. Large doorways 36 within the spa surround 34 provide easy access to the pump 26, motor 12 and switch box 18 for maintenance purposes.

[0018] As can be readily appreciated, maintenance on or replacement of the switch 14 is easily accomplished within the invention because the electrical motor 12 does not have to be opened to obtain access to the switch 14. Rather, the switch 14 is easily accessed by simply opening the switch box 18.

[0019] In a preferred embodiment of the invention, the invention is the variable speed electrical motor 12 described immediately above in combination with a switch 14, such as previously described above, for varying the speed of the motor 12, wherein the switch 14 is disposed external of the motor housing 16.

[0020] In another preferred embodiment of the invention, the electrical motor 12 is a variable speed electrical motor capable of operating at one of a plurality of discrete operating speeds. In the invention, the electrical circuitry for each of the plurality of discrete operating speeds includes both a start winding 40 for only that speed and a start capacitor 42 for only that speed. Such a circuitry (for a two-speed electrical motor 12) is illustrated in FIG. 3. Such a circuitry is contrasted with the electrical circuitry of variable speed electrical motors of the prior art wherein there is only one start winding and only one start capacitor for the entirety of the motor. The circuitry for such a motor is illustrated in FIG. 4.

[0021] The invention successfully overcomes the aforementioned problems in the prior art. By providing a switch for varying the speed of the motor external of the motor housing, prior art problems with rotating switch contacts and brush and ring configurations are eliminated. Moreover, by providing a separate start winding and a separate start capacitor for each speed in the motor, large amperage “spikes” are eliminated when switching the motor from a lower speed to a higher speed. For example, in one embodiment of the invention, the switching from a low speed to a high speed setting only caused an amperage “spike” of about six amps, whereas, in an otherwise identical motor of the prior art, amperage “spikes” of 50 amps or more are frequently encountered.

[0022] Having thus described the invention, it should be apparent that numerous structural modifications and adaptations may be resorted to without departing from the scope and fair meaning of the instant invention as set forth hereinabove and as described hereinbelow by the claims.

Claims

1. A variable speed electrical motor capable of operating at one of a plurality of discrete operating speeds, wherein the electrical circuitry for each speed includes both a start winding for only that speed and a start capacitor for only that speed.

2. An electrical motor combination comprising:

(a) a variable speed electrical motor capable of operating at one of a plurality of discrete operating speeds, wherein the electrical circuitry for each speed includes both a start winding for only that speed and a start capacitor for only that speed; and

(b) a switch for varying the speed of the motor, wherein the switch is disposed external of the motor housing.

3. The electrical motor combination of claim 2 wherein the switch is disposed within a separate switch box.

4. The electrical motor combination of claim 1 wherein the combination is disposed within a water recreational combination, the water recreational combination comprising:

(a) a water basin capable of retaining a human being partially submerged below a quantity of water;

(b) a water pump having a suction side and a discharged side; and

(c) water circulation conduits connecting the water basin to the suction side of the pump and connecting the discharge side of the pump to the water basin;

wherein the electrical motor drives the water pump.

5. A water recreational combination comprising:

(a) a water basin capable of retaining a human being partially submerged below a quantity of water;

(b) a water pump having a suction side and a discharged side;

(c) water circulation conduits connecting the water basin to the suction side of the pump and connecting the discharge side of the pump to the water basin;

(d) a variable speed electrical AC induction motor for driving the water pump; and

(e) a switch for varying the speed of the rotor, wherein the switch is disposed external of the motor housing in a separate switch box.

6. The water recreational combination of claim 5 wherein the water basin, the pump, the electrical motor and the switch box are enclosed within a spa surround.