Meters
We use CAT III meters in the elevator trade. What working voltage is this good for?
600 Volts
A step down transformer has more or less windings in the secondary windings?
Less
What does commutation mean?
Switching
What is armature reaction?
The distortion or reduction of the main magnetic field flux caused by the current in the rotating armature windings.
Interpoles are used to reduce armature reaction
A DC motor has fields and an armature. What does a AC motor have?
Rotor and stator
What does LoZ mean?
Low Impedance
Define inductance?
Opposition to current flow change in an electromagnetic device
When representing current flow there is an X and a dot. What direction does the current flow?
From the X to the dot
What is a compound generator?
It has both a series and shunt field
What is the RPM of a 6 pole 60 hz motor?
Formula:
Synchronous RPM = 60 × ƒ ÷ ( P/2 )
f = hz
Synchronous RPM = 60 (seconds) × f (Hz) ÷ (# Poles ÷ 2)
= 60 × 60 Hz ÷ (6 ÷ 2)
= 3600 ÷ 3
= 1200
What is the difference between continuity and resistance?
Continuity place low voltage to determine whether a path is open or closed.
Resistance is the reading of a circuit in ohms.
The secondary winding of a 2,300 to 115 V transformer has 18 turns. How many turns are there in the primary winding?
360 turns
How can we reduce ripple from a DC generator?
Adding more loops to armature
Field poles are made of thin laminations. Why are these poles not solid pieces?
The laminations reduce eddy currents and hysteresis losses.
FYI:
Occasionally, brass shims are used to intentionally reduce the strength of a pole piece for adjustment.
How does a squirrel cage induction motor interact with EMF?
Rides along on this sweeping magnetic field like a surfer rides the crest of a wave.
What symbol is diode test?
Cross with an arrow pointing left
Transformers are designed to comply with Department of Energy CFR 431.196 energy conservation standards. What efficiency does this standards require?
Above 97.7% efficient
Define Induction?
Induction is the creation of an EMF in a conductor through relative motion between the conductor and a magnetic field.
All ferrous materials retain an amount of residual magnetism after being magnetized. What circuit in a DC generator is used to stop this?
Suicide Circuit
A salesperson asks you what type of ac motor is needed to replace a bad motor on a hydraulic elevator? You will also be installing a new soft start with the motor.
Old motor info: across the line starter/ 460volt/ 15hp
A 6 lead 460 volt 15 hp motor
You are working on a 120 volt circuit. There are two 60 ohm resistors in series. What voltage should you read if you read across only one resistor?
60 volts
A 240 volt to 120 volt transformer has an open winding on the primary winding. What voltage will be read across the primary winding?
240 volt
Thumb=conductor motion
Index=Magnetic Field
Middle=EMF
You are troubleshooting a 1963 Otis elevator with an MG set. You notice the elevator seems to be jumping from leveling speed to high speed. What could possibly be the problem?
P.S. This is a Ward Leonard System
Check Resistor 1 - 3 and contacts 1 - 3
You get a call for a elevator not running. You check incoming and find a blown fuse on the three phase power. How should you proceed troubleshooting?
LOTO, check motor resistance and grounds