Bobby's final notes

What is a holding circuit also known as (3 other names)

1.)Seal in 2.)Memory logic 3.)Latching

Fault currents typically causes what kind of damages?

1.Melting/vaporizing conductors 2.arcing fires and explosions 3.severe insulation or electrical damage

What are 5 examples of motor failure

1.Single phasing 2.contaminants 3.old age 4.bearing failure 5.rotor failure

What is the benefit of using wye connected motors?

1.Used for dual voltage application 2.used for balancing load 3.less amperage on start up

Name 5 types of reduced voltage starters

1.wye/delta 2.auto transformer 3.primary resistor 4.VFD 5.solid state soft starter

Most motors are not designed to start more than ___ times per hour.

10

Force drying a motor is accomplished by applying ___% of the rated voltage to the motor for 2 to 4 hours to dry the coil.

10%

Overlords are sized to not exceed ______ of the rated FLA to the motor?

125%

Below what level of frequency will motors experience the highest motor losses?

15 HZ

A motor that has an insulation class testing A should not exceed ____°F

221°F

What are the voltage and amperage limits of SCR constructions

2500V and 3000A

The majority of industrial application normally use ________ motors.

3 ph induction

OCPDs must be sized to protect from fault currents they can range from _____ to _____

30KA to 200KA

A dual voltage wye connected motor has ____ separate circuits.

4

A motor started in wye configuration receives approximately ________% of the normal voltage and also approximately_______%

58% volts & 33% torque

A dual voltage wye connected motor (12 lead) has how many winding circuits?

6

A solenoid coil pulls how much times FLA on start up?

6 to 10 times

What is the approximate length of time it takes to transition from wye to delta in a closed transition starter

6-10 seconds

At what percent of RLA during wye delta closed transition starting does a motor transition from wye to delta?

85% of RLA

Which 3 ph motor starter mentioned in ch 15 is not considered an actual reduced voltage starter

Across the line

The NEC defines OL and overcurrent as what?

Any current in excess of the rated current of equipment or the ampacity of the conductor

What is the purpose and function of the 1M contactor

Applies line voltage to motor windings T1 T2 & T3 always pulled in

The _______ starting method provided the highest possible starting torque per ampere of the line current

Autotransformer

The amount of reduced torque is adjustable when using the ______ starting method which has taps

Autotransformer

________ starting is one of the most effective methods of reduced voltage starting

Autotransformer

Troubleshooting a solenoid coil NC 24V you measure 5 V at your solenoid what could be your diagnosis and why?

Bad common;bad supply voltage

What is not an example of a solid state switch?

Biacs

What is the purpose of the air gap in the armature

Break the magnetic field

Of all the OCPDs discussed which is the most sensitive to fault currents?

Circuit breakers

List 2 pros and cons each for water cooled starters

Con-terrible water quality & it requires more components Pro-water is an effective heat transfer medium & temp is easy to regulate

The _____ circuit determines when and how a motor starts

Control

An electric OL senses changes in

Current and temperature

What is the purpose and function of the 2M contactor

Delta or run contactor energizes T4 T5 & T6 of the motor to line voltage

_________ fuses are normally required for part winding starting

Dual element

What resistance should be read in the windings of a 3 ph motor?

Each windings resistance should be equal

What prevents S and 2M contractors from pulling in at the same time?

Electrical & mechanical interlocks

What is the benefit of the bypass contactor in a solid state starter

Eliminates need to cool starter

A IFM flow sensor trips because heat is pulled away from the sensor head, as the thermal conductive sensor is messing flow T or F

F

A three wire control circuit is not as safe as a two wire control circuit T or F?

False

Eddy current is the unwanted current generated in the metal structure of a device due to the rate of change in the DC magnetic field T or F

False

What are 2 separate ways motors are cooled in our industry?

Fans & fins

The maximum recommended acceleration time depends on the motor _____ size.

Frame

What is not a type of solenoid configuration 1.full port 2.plunger 3.horizontal action 4.Vertical action

Full port

________ starting is the least expensive and most efficient means of starting a motor for applications involving small HP motors.

Full voltage

What is the control point of the SCR?

Gate

What causes high temperatures in solid state starters?

Gates firing;SCR operation

What are 2 fault currents?

Ground fault & short circuit

What is used to remove heat from SCRs in these high temperature cabinets

Heat sinks

The longer a motor takes to accelerate the _______ the temp rise in the motor.

Higher

What is the definition of interrupting rating of a device?

Highest current at rated voltage that a device will interrupt the circuit.

Name the 3 most important motor nameplate information.

Hp RPM Frame

Explain the importance of of wiring both the low and high voltage contacts of an overlaod

If low voltage is not wired-single phases High voltage-will not open circuit no protection

Reduced voltage starting provides ______ current draw over a longer period of time

Incremental

What are the 3 main components of the VFD

Inverter Rectifier DC bus

How does wye delta reduced the voltage to the windings?

It reduces by connecting the windings in series or wye

What is the purpose and function of the line reactor used in the VFD starters?

It reduces harmonics

_______ is a type of motor control in which the motor may be bumped slightly

Jogging

What is the purpose and function of the capacitor in the DC capacitor bud bank?

Maintain voltage levels when voltage fluctuates

What type of starting method allows you to start or stop multiple motors independently of each other.

Multiple motor starter

What is the most common type of thermistor and the base temperature for standardizing all thermistors?

NTC; 77°F

What are 2 types of wye delta starters

Open transition Closed transition

How do you differentiate between the two types of wye/delta starters

Open transitions has 3 contractors and closed has 4

A _____ is a condition that occurs when the load connected to the motor exceeds the full load ampere rating of the motor.

Overload

An electrician can observe the even blackening of all motor windings that occurs when a motor has failed due to?

Overloading

Thirty percent of motors fail due to _____?

Overloading

List 3 ways a motor can overheat internally

Overloading Overcycling Poor air ventilation

When connecting a dual voltage 3 ph motor for low voltage are the windings connected in series or parallel

Parrallel

The motor stator windings must be divided into two separate electrical circuits of equal value when using ____________ starting method

Part winding

What is the difference from Ph to Ph short and Ph to ground short.

Ph to Ph short is when the motor windings insulation fails and the windings touch each other and Ph to ground is when the winding insulation fails and the winding touch the motor casing

Define plugging a motor

Plugging a motor forces a running motor in a reverse direction to rapidly stop the motor

List 2 pros and cons for refrigerant cooled starters

Pros-most efficient heat transfer method & uses the same refrigerant as the chiller Cons-repairs are more expensive & it requires sub cooled liquid

What is another name given to reproducing AC sine waves used in the DC circuit?

Pulse with modulation

How does a solid state starter start up and operate a motor?

Pulses to operate SCRs to slowly bring motor up to full speed; operate motor, mechanically loading and unloading

What is not a typical device used for a 2 wire control?

Pushbutton switch

Explain the proper procedure to troubleshoot a thermistor

Remove thermistor from the circuit, place in ice water 32°F, measure resistance, compare to manufacturers resistance.

A_______is the rotating part of the AC motor. The stationary part is the_______where the electromagnetic field is produced. This coil of wire allows electricity to pass through it without shorting wire to wire because it is__________.

Rotor Stator Enamel coated

Explain the procedure practiced to troubleshoot an SCR using a multimeter

Set your meter to the diode scale check for forward and reverse bias between the line voltage and the DC bus.

What is the purpose and function of the S contactor

Short or shunt contactor ties T4 T5 and T6 in wye configuration

___ is the operation of a motor designed to operate on 3ph but only operating on 2ph

Single phasing

What is the advantage of using VFD starting over solid state or other reduced voltage starting methods?

Speed can be reduced/RLA can be reduced electrically

On wye delta starters what contactors are energized in the following start to run sequence order?

Start-1M And 1S Transition-1M and 2S RUN-1M and 2M

______ voltage is any higher than normal voltage that temporarily exists on one or more of the power lines

Surge

Define thermistor

Temp sensitive resistor whose resistance changes with change in temperature

How is a motor rating affected when operating at altitude above 3300'?

The motor will derate or reduce capacity

What physically happens to a motor when it's running as the applied power's phase unbalance is increasing?

The motors temperature will proportionally increase as well.

Why do OL and fuses not trip or open on startup when the motor draws LRA (up to 6x FLA)

They have a time delay to overcome initial inrush current caused by high torque required to initially start the load.

What 2 methods are used to cause or start transition in closed transition wye-delta starters

Time delay or current

A _______ is provided in a primary resistor starting control circuit to short the resistors after the motor accelerates to a specified point.

Timer

Why does a soft starter use SCRs facing both directions per ph?

To allow positive and negative waves to be pulsed to motors

What is the reason for reduced voltage starters in general

To reduce inrush current

What is the main goal of using a reduced voltage starter with a 3 ph induction motor?

To reduce the large current draw or inrush current at start up

A motor will not start and the motor overloads will trip if the starting _______ is reduced too much.

Torque

Part winding starting usually classified as reduced voltage starting because of the resulting reduced current & _______

Torque

What is the purpose and function of the 1A contactor

Transition contactor energized transition resistors

A three ph motor can run on single ph power and go virtually undetected in some cases T or F?

True

Autotransformer starting may use its ________ advantage to provide more current on the load side of the transformer than in the line side

Turns ration

What are 3 ratings found on a fuse?

Voltage rating Interrupting rating Rating of the fuse (amps)

What are 3 ways solid state starters are cooled?

Water cooled (glycol) air cooled; refrigerant cooled

The _______ starting method is used when it is necessary to restrict inrush current to predetermined increments.

primary resistor