Electric Motors Study Guide

when a compressor is changed always

change the contactor

Motor Slip

internal motor component friction and resistance of connected mechanisms (often as percentages)

resilient, rigid, end, belly band

list the 4 motor mount types

True

mass to volume relationship would be described as Density

motor slip

the rotor speed drops below the stator speed, rotation rate of the magnetic field rotor increase which courses to create torque

FLA stands for

(Full Load Amps) rated amp draw when motor is full speed

LRA stands for

(Locked Rotor Amps) strictly to compressors or pumps, load can vary - chart needed

RLA stands for

(Run Load Amps) the amp draw on start up from stationary or is motor locked 5-7 times the FLA rating

IN YOUR OWN WORDS describe Boyles law and what it means, be descriptive

(inverse relationship with pressure and volume) compares two situations: before and after P1 x V1 = P2 x V2

N YOUR OWN WORDS describe Charles law, and what it means, Be descryptive.

(volume and temperature are always equal) V1/T1=V2/T2

Fahrenheit to Celsius

C = (F - 32) / 1.8

improper motor lubrication defective motor bearings improperly seated shaft

Excessive motor slip causes

Celsius to Fahrenheit

F = (1.8 x C) + 32

HP, voltage, amps, rmps

List the 4 things on a motor nameplate that are necessary to match when replacing an electric motor

Constant tourque ECM

Moderately efficient

False

1 KWH of electrical energy is the equivalent of 3314 BTU's

Single Phase commercial motors

200 - 575v (50-60 hz)

What is horsepower

(what power is rated in) the rate work is being done 300lb lifted 100ft per hr When a horse can lift 660 lb to a height of 50 ft in 1 min, it has done the equivalent of 33,000 ft-lb of work in 1 min, or 1 hp

Compressor

High starting torque

False

Horsepower is the rate of doing work

too much heat shorts the ground

How do brakers trip?

40,956

How many BTU/H would be produced in a 12-KW electric heater?

increases

If voltage to a motor decreases, amp draw will

Start

In a single phase compressor what winding measures the highest resistance?

5-7

In rush current (start up amps) are usually ------ times higher than the running amp

copper windings, battery, rod, wires, vents

Name at least 2 parts of an electric motor.

single phase

What are residential motors?

(Rated or Run) Load Amps RLA will always need a chart and FLA is striclty what it is supposed to be when running

What does RLA stand for and how does it differ from FLA?

service factory number of phases

What info do motors nameplates provide?

a motor is sealed inside a metal shell operates in a refrigerant vapor atmosphere

What is hermetically sealed?

friction and resistance from connected mechanisms bad motor bearings, improper seated shaft or motor lubrication rotors speed drops below the stator speed and the rotation rate of the magnetic fields rotor increases create torque

What is motor slip and what can cause it?

Multi- has multiple speeds Vari- any speed can vary

What is the difference between a multi speed and variable speed blower motor?

Explain how specific volume and density are related to each other.

they are the opposite of each other when a gas pressure decreases, the SV increases and D will decrease when a gas pressure increases, the SV will decreases and the D increases SV = 1/D D = 1/SV

Split Phase Motors

two separate motors windings good running efficiency medium amount of starting torque 1800 - 3600 rpms speed determined by the number of poles and method of wiring

stator

where the windings are located (starter speed)

dual voltage motors

wired differently for each voltage

False

Direct drive motors use a belt and sheave system

Single Phase residential motors

115 - 230v (50hz)

False

3 phase power will use more amps than single phase when completing a circuit with a load

Specific Gravity

A number that relates to the density of a substance with respect to the density of water is referred to as

1. power unit off 2. bring motor in 3. place belt in place 4. set motor back in place and tighten belt 5. use belt tool to check how tight the belt is

Explain to your knowledge the proper way to change a V belt on a HVAC unit.

Variable speed ECM

Most efficient

False

Motor winding insulation class "A" can handle higher temperatures than class "D"

False

Single phase compressor windings will all measure the same resistance from winding to winding (common, start, run)

False

The Mass of a substance is the product of a substance weight and the force of gravity pulling down on it.

Delta

The three phase transformer configuration that has a stinger/wild leg is the

Rectifier is AC to DC Inverter is DC to AC

What is the difference between a rectifier and inverter?

used on open motors to de-energize the start windings

What is the purpose of a centrifugal switch?

three phase

What phase motors do not have a state windings?

ball bearings require grease , motors (heavy load) sleave bearings require oil, motors (light load)

What type of bearings require grease, what bearings require oil for lubrication, and what type of motors are each bearing design primarily used for

Watt-hour

What unit of energy does the power company charge the consumer for?

the centrifugal switch opens to de-energize the motor

When a single phase motor gets up to 75% of its full speed. What happens and why?

False

When using pressure or temperature in an equation, it is important to use Celsius and PSIG

Start Capacitor

Which component can be wired into the starting circuit of a motor to improve starting torque?

Module

Which of the following is not a part of an electric motor?

control the speed of the compressor

Why do we need a rectifer for a inverted system?

what is matter?

any substance that occupies space and has mass made of atoms solid, liquid, gas

What is work

force moving an object Work = Force X Distance

pumps and compressors

have starting torque

mass

is the part of matter that is influenced by gravitational attraction

PSC motor

least effecient

Explain the difference in mass and weight

mass is a propety of matter, and responds to gravitational attraction (mases are attracted to each other) weight is not a property of matter, it is the force that matter uses to a supporting surface

gas, liquid, solid the states are determind by the heat content of the matter!!!

matter exist in what states?

IN YOUR OWN WORDS describe Daltons Law and what it means. be descriptive

relates the total pressure (93.6 kPa) of all gases in a mixture confined in a space contains hydrogen, helium, neon and argon