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| (IL) or several lights (SL) from such series circuits (Fig. 6-11), either for safety in having the lights electrically isolated from the main circuit, or when the lamps operate at different current ratings than the main circuit. |

| 8. Other transformers and autotransformers having characteristics special to their application include those for sign lighting (Fig. 6-12), fluorescent, mercury, sodium, and halogen vapor lamps, for motor starters, (Fig. 6-13), for x-ray equipment, for welding, for small intermittent use as in bells and annunciators. Ignition coils for use with internal combustion engines are also essentially two-winding transformers (Fig. 6-14). |

| STUDY QUESTIONS |

| 1. What is an autotransformer and where is it used? |

| 2. How does the operation of an autotransformer differ from that of the two-winding transformer? |

| 3. What are some advantages and disadvantages of an autotransformer? |

| 4. How are autotransformers connected in polyphase circuits? |

| 5. What is an induction voltage regulator and where is it used? |

| 6. What is a step-type regulator? What is it also called? |

| 7. What are instrument transformers and where are they used? |

| 8. How are current transformers (CT) and potential transformers (PT) connected in a circuit? |

| 9. What precautions should be taken with current transformers and potential transformers? |

| 10. What is a constant-current transformer and where is it used? |

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