Unit 18 Vocabulary

Question 1

Belly band mount motor

Answer 1

An electric motor mounted with a strap around the motor secured with brackets on the strap.

Question 2

Cradle mount motor

Answer 2

A motor with a mounting cradle that fits the motor end housing on each end and is held down with a bracket.

Question 3

Delta transformer connection

Answer 3

A transformer connection that results in a voltage output of 115V and 230V.

Question 4

Direct drive motor

Answer 4

A motor that is connected directly to the load, such as an oil burner motor or a furnace fan motor.

Question 5

Drip proof motor

Answer 5

A motor that can stand water dripping on it, such as a condenser fan motor in an outdoor condensing unit.

Question 6

End mount motor

Answer 6

An electric motor mounted with gas or studs fastened to the motor housing end.

Question 7

Explosion proof motor

Answer 7

A totally sealed motor and its connections that can be operated in an explosive atmosphere, such as in a natural gas plant.

Question 8

Frequency

Answer 8

The cycles per second (cps) of the electrical current supplied by the power company. This is normally 60 cps in the United States.

Question 9

Full load amperage (FLA)

Answer 9

A mathematical calculation used to get Underwriters Laboratories (UL) approval for a motor that was used by compressor manufacturer before 1972. FLA value was replaced with a rated-load amperage (RLA) value after 1972. It should not be used to determine the proper refrigerant charge, or to determine if a compressor motor is running properly.

Question 10

Hertz

Answer 10

Cycles per second.

Question 11

Locked rotor amperage (LRA)

Answer 11

The current an electric motor draws when power is applied to the motor, but its rotor is not yet turning. A rule -of-thumb often used by service technicians is that the LRA is normally five times the rated-load amperage (RLA).

Question 12

Motor service factor amperes

Answer 12

Any motor that has a service factor greater than 1 must have the service factor indicated on its nameplate. In some instances, the current the motor is drawing at its service factor loading is also indicated on the nameplate. This is usually expressed as service factor amperes (SFA).

Question 13

Rated load amperage (RLA)

Answer 13

A mathematical calculation used to get Underwriters Laboratory’s (UL) approval for a motor. The RLA value is used by a service technician to size wires, fuses overloads, and contactors for the motor. It should not be used to determine the proper refrigerant charge, or to determine if a compressor motor is running properly.

Question 14

Resilient mount motor

Answer 14

Electric motor that uses various materials to isolate the motor noise from metal framework. This type of motor requires a ground strap.

Question 15

Rigid mount motor

Answer 15

Electric motor that is bolted metal-to-metal to a frame. This type of motor will transmit noise.

Question 16

Thrust surface

Answer 16

A term that usually applies to bearings that have a pushing pressure to the side and that therefore need an additional surface to absorb the push. Most motor shifts cradle in their bearings because they operate in a horizontal mode, like holding a stick in the palm of your hand. When a shaft is turned to the vertical mode, a thrust surface must support the weight of the shaft along with the load the shaft may impose on the thrust surface. The action of a vertical fan shaft that pushes air up is actually pushing the shaft downward.

Question 17

Phase

Answer 17

One distinct part of a cycle.

Question 18

Wye transformer connection

Answer 18

Typically furnishes 208V and 115V to a customer.