106 Electricity
A motor has a shorted winding if any of the resistance measurements are:
0 ohms
A megohm reading of _____ or higher indicates that a motor's winding insulation is in excellent condition.
100 megohms
The synchronous speed of a four pole, 60 Hz single phase motor is:
1800 RPM
Which of the following is an acceptable temporary replacement for a run capacitor rated at 35 MFD @ 440VAC:
37.5 MFD @ 440 VAC
The locked rotor amperage of a motor is normally __________ times greater as the running load amperage.
4 to 6
When checking the windings of a polyphase motor:
All three winding terminals show the same resistance.
In a capacitive circuit
Amps leads volts
Which meter is used to bench check a motor for shorts or open windings?
An ohmmeter
A split phase motor that has a current relay and start capacitor is called a:
CSIR motor
A ________ is commonly used on a single phase capacitor start fractional horsepower compressor motor to disconnect the start winding after the motor starts.
Current relay
The _____________________ is wired in series and operates from in rush amps.
Current starting relay
A PSC motor that is running and up to speed will have the start winding:
De-energized
Resistance can be calculated by:
E divided by I
With a motor running at full load, voltmeter leads are placed on L1 and T1 terminals of the contactor. The voltmeter indicates no measurable voltage. This is an indication of:
Good clean contacts.
When testing a motor with an ohmmeter, the following measurements are recorded, Common to run 4 Ohms, Common to start 6.2 Ohms, Run to start 10.2 Ohms, and Common to ground 20.4 Ohms. This indicates a/an:
Good safety ground.
A CSR motor provides:
High running and high starting torque.
The shaded pole motor has:
Little starting torque.
What connects to the terminals T1, T2 & T3 on a contactor or motor starter?
Load connections
An ECM is designed to:
Maintain constant torque or velocity
Electrical insulation testers are often called:
Megaohmmeters
Impedance is:
Opposition to alternating current flow.
A split phase motor that has a run capacitor only is called a:
PSC motor
The function of the defrost termination, fan delay thermostat is to:
Terminate the defrost cycle. Delay the fans from operating.
What is continuous voltage?
The BEMF voltage of a potential starting relay coil.
What is drop out voltage?
The BEMF voltage required to hold the contacts closed to a potential starting relay.
What is full voltage current?
The amount of current required by a motor to produce full load torque at the rated speed of the motor.
Continuous Voltage
The back EMF operating voltage of a potential starting relay coil.
When using a defrost time clock, a defrost cycle is initiated by:
Time
When using a defrost time clock, a defrost cycle is terminated by:
Time. Temperature. Pressure. Correct! All of the above.
What is the function of the start winding?
To split the phase and start the rotor rotating.
Back EMF is produced in the start winding by magnetic induction from the run winding.
True
In a capacitive circuit, volts lags amps.
True
Define torque.
Turning twisting force.
Capacitors are always connected _______ to the start winding.
in series
Capacitors are always connected ________ to the start winding.
in series
The stator windings of a dual voltage polyphase motor are connected for high voltage
in series
The start winding is out of phase with the run winding by:
physical placement, resistance, inductive reactance
The disadvantage of part winding start is that of _____ ______ _______.
poor starting torque
Like charges
repel each other
A split phase motor has a ______ winding and a ________ winding.
run. start
Start and run capacitors are added to the:
starting winding
Which of the following is the symbol for Impedance in an AC circuit?
z
Which of the following electrical test instruments can be used to check for short circuits, open circuits and shorts to ground?
An ohmmeter
The function of a multimeter that allows a field technician to test for an unbroken path in an electrical device or between two points of a circuit is:
Continuity
What motor factors should be considered when selecting a reduced voltage start method?
Current and torque
Three phase motors are commonly _________ motors because the stationary windings are arranged in pairs.
Dual voltage
Motor windings have a single pole.
False
The construction of a capacitor allow continuity through the device.
False
To reverse the rotation of a three phase motor, a technician must switch out any two:
In coming power leads
When testing a capacitor with an analog or digital ohmmeter, the meter should
Measure low resistance then return to a high reading.
An electronically commutated motor (ECM) is designed to:
Provide proper air flow under various conditions
An electronically commutated motor (ECM) is designed to:
Provide proper air flow under various conditions.
Which of the following is considered a capacitive load?
Start capacitor
The power connection to the ECM can only be pulled after the equipment has been de-energized for at least 5 minutes.
True
The replacement of a Genteq ECM is OEM brand and model specific.
True
To discharge a capacitor prior to ohmmeter testing:
Use a 15,000 or 20,000 Ohm, 2 to 5 Watt resistor across the terminals.
In a resistive circuit:
Volts and amps are in phase.
In an inductive circuit
Volts leads amps
Which of the following is the correct formula for determining wattage in an electrical circuit?
W=E times I.
When working with three phase power, voltage imbalances should be less than ____ and current imbalances should be less than ______ .
2%, 10%
An ohmmeter should never be connected to
A charged capacitor until it has been discharged.
A split phase motor can use a ______ to energize and de-energize the start winding
A potential starting relay. A current starting relay. A PTC relay. All of the above.
Which type of circuit has a power factor of one?
A resistive circuit.
Before testing a capacitor or measuring its capacity, the field technician must discharge the capacitor using:
A resistor
Define split phase motor.
A single phase motor that auxiliary start winding 45-99 degrees electrically away from the main winding.
A CSR motor has:
A start and run capacitor
Pick-up voltage
Back EMF voltage range required to energize the coil of a potential starting relay and open the set of normally closed set of contacts.
The _____________________ disconnects the start winding from motor speed
Centrifugal switch
Which of the following motors are most efficient?
ECM
Which of the following would be considered and inductive load?
Electric motor
Which of the following is considered a resistive load?
Electric strip heater
The Law of __________ is the principle behind the rotation of a motor.
Electrical Charges
What are the reasons for using reduced voltage star?
Electrical interference. Demand amperage usage. Amperage supply by the utility company. All of the above.
Define time clock
Electronic or electro-mechanical device that changes position of contacts to initiate an action based upon specific a time.
ECM is defined as:
Electronically Commutated Motor
Which of the following is NOT a factor in determining impedance in a circuit?
Frequency
The capacitor start-capacitor run (CSR) motor provides:
High starting and running torque
The symbol for current is:
I
Voltage can be calculated by:
I times R
The stator windings of a dual voltage polyphase motor are connected for low voltage
In parallel
If the conductor in an AC circuit is wound into a coil, the resulting EMF opposes the supply voltage. This opposition is called:
Inductive reactance
What statement is NOT true about a start capacitor.
Its dielectric consists of an ink type liquid
Capacitors are rated in:
Microfarads and volts
Drop Out Voltage
Minimum back EMF voltage required to hold the contacts closed to a potential starting relay.
A motor has an open winding if any of the resistance measurements are:
OL or infinite
Single phasing of a three motor occurs when ______ phase leg is lost.
One
The ____________________ removes the start winding from the motor circuit by a change in temperature.
PTC
The _____________________ is wired in parallel and operates from back EMF.
Potential starting relay
A voltage drop only exists if there is _______ between two points.
Resistance
A capacitor analyzer is designed to read
The capacitance of a capacitor
When identifying the windings of a single phase motor
The common to run terminals show the lowest resistance
When testing the windings of a single phase motor:
The common to run terminals show the lowest resistance
When identifying the windings of a single phase motor:
The common to run terminals show the lowest resistance.
What is pick up voltage?
The minimum BEMF voltage required to open the normally closed potential starting relay coil.
Single phase motor speed is determined by the:
The number of stator poles.
In a single phase motor, which winding has the lowest resistance?
The run winding
What information must a technician have to properly replace a capacitor?
The voltage rating, capacitance rating and whether it is a start or run capacitor
A positive temperature coefficient (PTC) start device is a type of:
Thermistor
