Fire & AC motors

Question 1

2 types of fires

Answer 1

• Slow-may not ignite,very smoky
• Fast-Ignites quickly,flames quickly

Question 2

4 types of detector heads

Answer 2

1. Optical-Scattering of light by smoke to receptor
2. Heat-measuring heat in room
3. Infra red-phototransistor detects flicker produced by smoke
4. Ionisation-current in chamber reduced when smoke enters chamber

Question 3

How AC inductor works

Answer 3

• 440v 3ph 60hz applied to stator
• rotating mag field set up in windings
• EMF induced in rotor which interacts with stator rotating field
• Torque applied to rotor

Question 4

A

ADV + Disadv of ac induct motor

Answer 4

+
Smaller,simplier,easy to maintain,no elec connect betwn rotor & stator

- High starting I,High fuse rating,
poor speed control