Basic Operation

Bidirectional motors - those that can rotate in either direction – are of two classes: 1. Reversing motors, which can change from full speed in one direction to full speed in the opposite direction. 2. Reversible motors, which can be reversed only when the motor is not running, or is running below cut out speed. Some motor manufacturers distinguish between quick reversing and instant reversing. A quick reversing motor requires a time delay of approximately 1/25th of a second or more for the switching circuitry to react. An instant reversing motor requires absolutely no time delay. The standard SINPAC Switch can be used on reversible and reversing motors. The SINPAC IR Series Switch provides the function of a direction sensing centrifugal switch and makes a reversible capacitor start motor into an instant reversing motor.

In order to reverse a single-phase motor, it is necessary to reverse the polarity of either the start or main winding, but not both at the same time. The reversal of the winding is accomplished with an external reversing switch or contactor that is not part of the SINPAC Switch. SINPAC Instant Reverse Switch is not dependent upon how quickly the user operates the reversing switch, but only that the reversing switch did change states, i.e., forward to reverse, or vice versa. The SINPAC Switch detects the change in the phase shift between the main and start windings, and the logic circuit instantly actuates the starting switch, causing the start circuit to be reconnected to line voltage. This connection causes the motor to decelerate and then reaccelerate in the opposite direction. The SINPAC IR and IVR Series switches interrupt the start circuit current after the motor has accelerated to the cut out speed, and reconnect the start circuit whenever the circuit senses the motor speed has fallen to cut in speed (usually about 50% of synchronous motor speed).

1. Electrically Protected: Designed to filter out electrical noise, so there is no concern of random switch malfunction.

2. Universal Design: 50/60 Hz operation. Will work on 2, 4 or 6 pole motors of any manufacturer. Reduced inventory.

3. Line Voltage Compensation: No modifications or changes are required for line voltage variations. SINPAC Switches will operate in areas susceptible to brown-outs or low voltage due to long wiring runs. Line voltage compansation results in less stress on the starting capacitor due to overvoltage.

4. Reduced Installation Time: Easily accessible 1/4 inch terminals and mounting, reduce the amount of time required to install SINPAC Switches or to change out mechanical switches.

5. Transient Protection: Transient protection tested per IEEE C62.41 – 1991 Category A3.

6. Soldered Heat Sink: High cycling.

7. Phase Comparator Logic: Allows Instant Reverse operation (no time delay).

8. Restart Capability: When motor speed drops below 50% of synchronous speed, the start circuit is reconnected to reinitiate starting torque.

9.Environmentally Protected: Immune to moisture, dust, dirt, shock and vibration.

Selection

Motor hp ratings are typical. For an accurate selection procedure, measure start capacitor current during a normal start or at locked rotor and select a SINPAC Switch with higher maximum current rating than that measured.

1. Be sure switch series matches motor type.

2. Be sure switch voltage rating matches auxiliary (start) circuit voltage rating.

3. Selection can be based on actual measurement of start capacitor current or two times the motor nameplate FLA rating.

4. Switch current rating must match or exceed the motor start capacitor current requirements. Always select a SINPAC Switch with the next higher current rating for:

  a) High cycling applications.

  b) Long acceleration time.

  c) High ambients: Greater than 55° C.

5. To assure proper motor operation, the voltage across the start winding must reach the SINPAC Switch cut out reference voltage between 70% to 85% of motors synchronous speed. SINPAC Switches are line voltage compensated. Changes in the line voltage will not effect system operation unless an overload condition causes reduced running speed, along with reduced voltage across the start winding.

6. Higher current switches can be used in place of lower rated switches of the same series.

Line Voltage Compensation Charts

  Induced voltage across the start winding is directly proportional to motor speed and line voltage. All SINPAC Switches use this voltage to switch the start capacitor out of the circuit. Your motor with a SINPAC Switch must generate a voltage greater than the switch cut-out voltage to assure cut-out of the start capacitor. Refer to charts ABOVE.