Materials:

1. Ugly’s Electrical References or National Electrical Code Book
2. Allen –Bradley Heater Table
3. Heaters
4. Fuses
5. Starter

Purpose:
The purpose of this exercise is to teach the trainee how to size fuses, overload protection, wiring, and conduit for a motor circuit.

Procedure:
Complete the calculations for each of the steps below.  After completing your calculations select the proper heater and fuse sizes for the circuit in the drawing. 

1. Size heaters for M1 and M2 using Allen-Bradley Table 150.
2. Calculate branch-circuit conductor’s amperage rating and size conductors and conduit for M2. Use THHW 75 deg C copper wire and rigid conduit.
3. Calculate branch-circuit short-circuit and ground-fault protection for M2 using dual element fuses.
4. Calculate feeder conductor’s amperage rating and size conductors and conduit. Use THHW 75 deg C copper wire and rigid conduit.
5. Calculate feeder short-circuit and ground-fault protection for both M1 and M2 using dual element fuses.

Quiz:  Motor Protection

1. A short-circuit or ground fault current is an excessive current which ______________________.
   1. is confined to the normal conductive path
   2. flows outside the normal conducting path
   3. does not flow
      
      
2. An overload current is an excessive current which ________________________.
   1. is confined to the normal conductive path
   2. flows outside the normal conducting path
   3. does not flow
      
      
3. Short-circuit current levels can be ____________ times that of normal operating current.
   1. 6 to 10
   2. 2 to 5
   3. hundreds of
   4. zero
      
      
4. List four operational characteristics, specs, or information given on a Motor Name Plate.
   1.  
   2.  
   4. 
      
      
5. Overload currents are ___________ times that of normal operating current.
   1. 1 to 2
   2. 100 to 1000
   3. 6 to 10
   4. 15 to 30
      
      
6. When sizing conductors for a motor branch circuit, the conductors should have a current carrying capacity rating of no less than ______% listed full-load current of the motor.
   1. 100
   2. 125
   3. 150
   4. 200
      
      
7. When sizing dual element fuses for motor branch circuit protection, the fuses should be rated at no less than ______% listed full-load current of the motor.
   1. 100
   2. 150
   3. 175
   4. 225
      
      
8. A _________ fuse can be sized closer to the full-load current of a motor.
   1. single-element
   2. dual-element
      
      
9. An example of motor branch-circuit overcurrent (short-circuit and ground fault) protection is a(n)
   1. feeder
   2. overload relay
   3. temperature detector
   4. dual-element fuse
      
      
10. The motor-running overcurrent protection device is usually a(n)
    1. instantaneous-trip breaker
    2. dual-element fuse
    3. overload relay
    4. nontime-delay fuse