CA2020205A1 - Reversing motor controller - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The disclosure describes a motor reversing control that employs a run and direction relay together with a switching control circuit that can be used to start, stop or reverse alternating or direct current reversible motors.

Description

Title: REVERSING MOTOR CONTROLLER 20202 Inventor: David John Zantingh BACKGROUND OF THE INVENTION ;
' This invention relates to controllers for reversible electric motors, in particular to a motor reversing control. The present invention is particularly useful as a control for automated or manual shading systems employed in greenhouses or ,~ ;
for use in venting systems, but may be used in any application where a motor reversing control is employed .
In environments where a degree of control is desired over the amount of exposure to sunlight, such as in greenhouses, ~ --shading systems are often employed. These systems can range from completely manual systems employing no motorized components to electronically programmed motor driven systems that operate ;
entirely on an automatic basis.
Motorized systems typically employ reversible motors to ~15 allow the opening and closing of the shading apparatus to be accomplished with a single motor. A motor control is connected between the motor and its power source to determine the direction ~-the motor is to run'. Inputl!signals to the controljare received via manual switching or by automated circuitry.
~2~0 ~ Existing motor controlfi routinely contain a pair of 202020~

three-pole or four-pole relays or contactors. ("contactors") One contactor is wired so that when activated the motor will start in one direction while the other contactor is wired so that once activated the motor will run in the opposite direction.
Only one contactor is activated at a time, depending on which direction it is desired for the motor to turn.

SUMMARY OF THE INVE~TION
The present invention is directed towards providing an improved motor control, being less expensive to manufacture and repair, smaller, lighter and more reliable.
~ n the present invention, the contactors typically used in these types of motor controls are replaced with dedicated run ' ' ' ~ ' " b)T r and start relays. The reduced size of the relays in relation to the contactors enables a smaller and less expensive housing to be ~ -~ . . ^;.
utilized for the entire motor control. This facilitates storage ~
and the ease of installation as well as increasing the possible ~ ;
sites for installation. In addition, the relays cost only a ~ fraction of the price of the contactors, further reducing the ;~20 cost of the entire motor control.
, ; The relays can also be driven with a lower current than can the contactors. This allows a less expensive low voltage c;ontrol or switching~circu,it ~o drive the relays. Currently, more expensive higher current control circuits are required to drive the contactors.

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The relays are connected to the control circuit which together form the reversing motor control. The control is placed between the motor power source and the alternating current or direct current reversible motor.
Further features of the invention will be described or will become apparent in the course of the folIowing detailed ~-~. !':'.: ' ' description.

BRIEF DESCRIPTION OF THE DRAWINGS ~-In order that the invention may be more clearly understood the preferred embodiment thereof will now be described ~;~
in detail by way of example, with reference to the accompanying drawings, in which~
Figure 1 is a block diagram of the motor control .
showing detail of the switching mechanism.
Figure 2 are possible variations for the run relay.
Figure 3 are possible variations for the direction relay.
Figure 4 is a schematic of the complete motor ~20 ~ aontrol.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
, Referring to Flgurell, the diagram shows la preferred embodiment for a dual voItage alternating current single phase reveroible;motor, configured to operate at its higher voltage.
~25~ ~"ACl" is the alternating current power source for operating the motor. It ~02a~

should provide the proper voltage, frequency, disconnecting means, overcurrent and overload protection, as required by any safety regulations.
"Kl" is the run relay. It provides a means of starting and stopping the motor. When the contacts are closed, it completes the circuit and allows the voltage from ACl to be applied to the motor, thus starting it. When the contacts are open, it interrupts the circuit and prevents the voltage from ACl from reaching the motor, thus stopping it. It is not necessary to interrupt all the lines in order to stop the motor. However, it is possible using a multi-pole relay, as shown in figure 2A, and may be desired if this relay is to provide the disconnecting means as well.
A snubber may be connected across the contacts of the relay to prolong contact life as shown in figure 2B.
It is not important that the arm of the relay is on the power side as it may also be connected to the load side as shown ' in figure 2C.
It is also possible to use more than one relay, either -~20 in series~or in parallel or on each line, as shown in Fig. 2D.
Figure 2E shows a variation using triac or solid state ~: :
relays.

~ormally t,he relays are connected using normallylopjen . ~.: .
contacts. This means that when the coil is activated the 25~ contacts close and the motor starts. Although definitely not '::

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advisable, it is possible to hook a relay up so that when the ~
coil is activated the motor stops as depicted in figure 2F. ~;
"K2" is the direction relay. It connects the start winding/centrifugal switch/capacitor ("start winding") to the motor circuit. When activated it will reverse the polarity of the start winding with respect to the run winding. This will cause the motor to start in the opposite direction once power is applied.
It is possible to switch the leads of the start winding -between the center tap of the run winding and one power line.
This can be accomplished using a double pole relay as shown in figures 3A and 3B. Either of these configurations may be desirable if the motor's overload is to provide overload protection for the motor as well. Alternatively, a llne may be ~ ;

returned, after the overload, to the relay as shown in figure 3C.
Although not advisable, it is possible to switch the -~
polarity of the run winding in order to reverse the ~-direction as shown in figue 3D.

~20 ~ It is not important in which order the ; ;
; start wind;ing/centrifugal switch/capacitor are arranged, as they are~ connected in series.

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`~ , However arranged, the function of K2 is to start the motor~in~one direction, (when power is applied from Kl) when it s~actlvated and in the other direction when it is deactivated.

20~2 .
K2 can also consist of several solid state relays.
One of the advantages of using a direction relay in the start winding is that it need only carry the start winding current for a brief instant. As it is set up in its proper orientation before power is applied, the direction relay will never have an arc across its contacts, allowing a smaller relay to be employed.
"CCl" is the control circuit. Its function is to provide the signal to actlvate, or deactivate Kl and K2 at the appropriate times. The input signals for the control circuit may be received from either a manually activated switch or from some . .: i, "
automated device. The input signals will typi~ally command the ; ~ ;
circuit to either start the motor in a clockwise direction, start ~-the motor in a counter-clockwise direction, or stop the motor.
~5 The circuit is designed so that when starting the ~ ~ `
motor, CCl provides K2 with a signal before it provides Kl with its signal. If Kl and K2 were activated simultaneously arcing -`~
might;occu~r across the contacts of K2. K2 is set up prior to Kl being activated to prevent the motor from starting in the wrong ~20 ~ dl~r-ction-; The circuit is wired so that when the input signal commands the control circuit to change the motor direction Kl .:
remains open long enough,t!ojal,low thje motor to stop befo~re applying power to start the motor again in the opposite 25~ direction. This delay is required to allow the centrifugal : ~

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switch in the motor to close thus including the start winding in the circuit again, and thereby preventing the motor from continuing to run in the wrong direction.
When the input signal to the control circuit commands the motor to stop, CCl signals Kl to open almost instantaneously.
This signal is delayed only long enough to prevent noise spikes from signaling the motor to stop.
"Ml" is a 230/115 volt, signal phase, reversible motor ~
configured to operate at 230 VAC. One lead of the start winding ~-is connected to the junction of the run windings. Different motors would necessarily require different configurations of K2.
Figure 4 is a complete schematic of a motor control using this configuration.
It will be appreciated that the above description ., .
related to the preferred embodiment by way of example only. Many ~; variations on the invention will be obvious to those knowledgeable in the field, and such obvious variations are within the scope of the invention as described and claimed, whether or not expressly described.
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Claims (5)

1. An electrical circuit for starting, stopping or reversing alternating or direct current reversible motors, consisting of dedicated run and direction relays and a switching control circuit.

2. A circuit as recited in claim 1, in which 3-pole or 4-pole contactors have been replaced with dedicated run and direction relays.

3. A circuit as recited in claim 2, in which the direction relay is first set up activated or deactivated, depending on direction when the control circuit receives a reverse input signal. When a change direction command is received, the run relay releases first, then the direction relay switches position, then the run relay re-activates.

4. A circuit as recited in claim 3, in which a relatively low current control circuit is employed.

5. A circuit as recited in claim 4, in which a spark absorbing snubbing circuit is wired in parallel to the dedicated run relay.