Questions for test

3 heat switch: if there are two elements and each have a resistance of 100 ohm, and voltage is 230V, what its resistance and power will be in high, medium and low position?

simmestat: how does simmestat work on a stove hotplate or grill on and off in a fixed cycle.

motor:Can u tell 4 types of single phase motor ? And how do they work by?

net work :How to calculate resistance and current of a hearter which has label states 2200W,230V ?  

appliance test : what's the propuse of the appliance test?

protecting: 25A fuse has a fusing factor of 1.5, what's minimum fusing current is? 

SHADED POLE MOTOR

A shaded-pole motor is one type of AC single-phase induction motor. It is basically a small squirrel cage motor in which the auxiliary winding is made of a copper ring surrounding a portion of each pole.This auxiliary winding is called a shading coil. Currents in this coil delay the phase of magnetic flux in that part of the pole enough to provide a rotating magnetic field. The direction of rotation is from the unshaded side to the shaded (ring) side of the pole.The effect produces only a low starting torque compared to other classes of single-phase motors.

These motors have only one winding, no capacitor nor starting switch, making them economical and reliable. Because their starting torque is low they are best suited to driving fans or other loads that are easily started. Moreover, they are compatible with triac based variable-speed controls, which often are used with fans. They are built in power sizes up to about 1/6 hp or 125 watts output. For larger motors, other designs offer better characteristics.

PSC Vs SLIPT PHASE MOTOR VARIANT

• Permanent split capacitor motors compare split-phase motors with one crucial differernce. The PSC motor has a run capacitor,eliminating split-phase motor's BIACcentrifugal switch and using the start windings during operation.
• Benefits of a PSC Motor:

1.  No entrifugal switch to fail
2.  better performance&less slip
3.  less heat buildup&more frequent starts
4.  lower cable costs&lower operating costs
5.  smoother,quieter operation

INDUCTION CSRC MOTOR & CSIR MOTOR

• induction is used primarily to fill the need of motors using a single phase motor for efficiency reasons. So rather than having to modify three phase motors to run in single phase, the motor is instead changed to single.

• CSIR MOTOR

A start capacitor is connected in series with the start winding of the CSIR motor to provide a larger phase shift when voltage is first applied to the motor. The increased phase shift causes a stronger magnetic field to pull on the rotor to cause it to begin to spin.

The start capacitor can provide large amounts of capacitance for a short period of time, such as during starting. After the motor is started, the capacitor must be removed from the circuit so that it won't overheat. This is accomplished with the end switch. The electrical diagram in this figure shows the capacitor connected in series with the start winding. When voltage is first applied to the motor, both the start winding and the run winding will be energized. When the rotor reaches nearly full rpm, the end switch will open and disconnect the start winding and capacitor from the circuit. That is, no current will flow through either the start winding or the capacitor and they can cool down and be ready for the next time the motor is started. When the motor is de-energized and the rotor slows to a stop, the end switch is closed again and the start winding and capacitor are reconnected to the circuit for the next start.
Since the start capacitor is physically mounted on top of the motor, a metal cover is placed over it to protect it from damage. Since the capacitor’s case is made of plastic, it can easily be cracked and damaged if the motor is used in a harsh industrial environment.

• CSRS MOTOR

CSCR and CSIR controls both start a motor the same way-with a “start capacitor” that shifts the motor’s electrical phase slightly, creating starting torque. As the motor approaches running speed (in about 1/3 second), a relay in the control opens, removing the start capacitor from the circuit. Here’s where the controls differ.

Conductors and Insulators

• conductors: Gold, sliver, copper, aluminum
• insulators: Teflon, mica, glass, rubber-like polymers

• 

  Different types of insulators have different properties. Such as high thermal resistance, resistance of pressure, and insulating strength, which can fit different requirements of working environments. Also for different conductors have different properties of electric conductivity.
• temperature: the high temperature of working environment will lead insulators to broken easier than usual.
• 
  

  tensile strength: for example, Unit cross-sectional area of insulating material can withstand the tension, for example, cross-sectional area per square centimeter of glass can withstand the pull of Newton 1400.

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