Chapter 17- Servicing Electric Motor and Controls

A hermetic compressor motor has a short in one its winding if any of the resistance measurements are near?

0 omega

To make sure an electronically commutate motor (ECM) is communicating with the HVAC system, a technician should check the ?

120 V power circuit and control circuit

To approximate a motor's internal temperature, a technician can add_________to the temperature of the motor frames as measured by an infrared thermometer.

20 degrees

The temperature of the hottest part inside a motor should not be more than________above the ambient temperature.

72 degrees

What indicates that a motor has excessive endplay?

A distinct knocking sound, Excessive Vibration, Excessive heat on the motor shaft

A cylindrical sleeve bearing, typically made of bronze is called a?

Bushing

What type of electrical instrument wraps around the conductor it is measuring?

Clamp-on ammeter

What multimeter function allows a technician to test for an unbroken path between two points in a circuit?

Continuity

If a refrigeration unit is undersized for its application, the compressor motor will most likely fail because it is running?

Continuously

The____function on a multimeter allows a technician to test devices that conduct current in only one direction

Diode check

Megohmmeters are used to test?

Electrical Insulation

When a control unit's diaphragm or bellows compresses easily, it indicates that the?

Element has lost its charge

What type of electrical instrument must be connected in series to take an accurate reading?

In-line ammeter

Loose electrical connections create excessive resistance and can cause a fan motor to?

Lose Speed, Hum Loudly, Overheat

What type of electrical instrument can be used to check for short circuits, open circuits and shorts to ground?

Ohmmeter

What type of electrical instrument can only take an accurate reading when a circuit's power is turned off?

Ohmmeter

Which type of lubrication method is considered permanently lubricated?

Oiliness bushing

The centerline of the shaft on a belt-driven fan or compressor must be perfectly________with the centerline of the motor shaft.

Parallel

To measure voltage polarity correctly in a DC circuit, a technician should place the voltmeter's red lead on the side of the load closet to the_____side of the power supply.

Positive

What instrument shows the relationship between a circuit'a true power and apparent power?

Power factor meter

A grooved wheel with two flanges used to change rotational direction or provide mechanical advantage is a_______?

Pulley

By widening the groove of a variable-pulley, a technician________the speed belt-driven blower or fan.

Reduces

A technician should repair a control unit with corroded contacts by______the contacts

Replacing

A voltage drop only exists if there is a______between two points in a circuit.

Resistance

All three sets of winding in a three-phase motor must have the same?

Resistance

Before testing a capacitor or measuring its capacitance, a technician must discharge the capacitor using a high value___________

Resistor

If a single-phase external motor is humming but not starting, the first step is to check the?

Start Capacitor

Which instrument measures only the true power consumed by electrical load?

Wattmeter