Category: Electric Motors

Identifying Motor Capacitor Terminals

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Identifying Motor Capacitor Terminals

Most run capacitors and some starting capacitors are of the oil-filled type. This is especially true for high current motors such as those used to operate compressors. Many manufacturers of oil-filled capacitors will identify one terminal with an arrow, a painted dot, or by stamping a dash in the capacitor can, Figure 11–27. This identified …

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Permanent Split Capacitor Motor

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Permanent Split Capacitor Motor

The permanent-split capacitor motor has greatly increased in popularity for use in the air conditioning field over the past years. This type of split-phase motor does not disconnect the start windings from the circuit when it is running. This eliminates the need for a centrifugal switch or starting relay to disconnect the start windings from …

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Motor Power Consumption

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It should be noted that the motor does not use less energy when connected to 240 volts than it does when connected to 120 volts. Power is measured in watts, and the watts will be the same regardless of the connection. When the motor is connected to operate on 240 volts, it will have half …

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Dual Voltage Motor

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Dual Voltage Motor

Single-phase motors can also be constructed to operate on two separate voltages. These motors are designed to be connected to 120 or 240 volts. A common connection for this type of motor contains two run windings and one start winding, Figure 11–17. The run windings are labeled T1–T2, and T3–T4. The start winding is labeled …

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Testing The Stator Winding

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Testing The Stator Winding

The stator winding of a single-phase motor is generally tested with an ohmmeter. The ohmmeter test can be used to determine if a winding is open or grounded. Many single-phase motors have one lead of the run and start windings connected as shown in Figure 11–15. To test the windings for an open, connect one …

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Capacitor-Start Induction-Run Motors

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Capacitor-Start Induction-Run Motors

Capacitor-start induction-run motors are very similar to resistance-start induction-run motors. The design of the stator winding is basically the same. The main difference is that a capacitor is connected in series with the start winding, as shown in Figure 11–11. Inductive loads cause the current to lag the applied voltage. Capacitors, however, cause the current …

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Resistance-Start Induction-Run Motor

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Resistance-Start Induction-Run Motor

The rotating magnetic field of the resistance-start induction-run motor is produced by the out-of-phase currents in the run and start windings. Since the run winding appears more inductive and less resistive than the start winding, the current flow in the run winding will be close to 90 degrees out-of-phase with the applied voltage. The start …

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The Effects of Voltage Variations on AC Motors

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The Effects of Voltage Variations on AC Motors

Motors will run at the voltage variations already mentioned. This does not imply such operation will comply with industry standards of capacity, temperature rise, or normally anticipated service life. Figure 7-34 shows general effects. Such effects are not guaranteed for specific motors. The temperature rise and performance characteristics of motors sealed within hermetic compressor shells …

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Potential-Type Relay

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Potential-Type Relay

This relay is generally used with large commercial and air-conditioning compressors (see Fig. 7-31). Motors may be capacitor-start, capacitor-run types up to 5 hp. Relay contacts are normally closed. The relay coil is wired across the start winding. It senses voltage change. Start winding voltages increase with motor speed. As the voltage increases to the …

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Current-Type Relay

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Current-Type Relay

The current-type relay is most often used with small refrigeration compressors up to 1 hp. Where power is applied to the compressor motor, the relay solenoid coil attracts the relay armature upward. This causes bridging contact and stationary contact to engage (see Fig. 7-30). This energizes the motor start winding. When the compressor motor comes …

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