UNIT 18: APPLICATION OF MOTORS

On any given motor, there will be the manufacturer and the model number. The manufacturer sticker will give most of the power supply information, including:

1. Voltage

2. Current capacity in amperes

3. Frequency in hertz/cycles per second

   1. Phase

Every motor operates around +/- ____ % of its rated voltage

10%. Ie a 208 v motor can operate 228.8 to 187.2

Explain why a motor that is receiving too low of voltage would overheat

If the voltage is lower than expected, the motor’s current draw will go up, because its trying to do its job but lacks the power to do so. As the motor draws this high current it will eventually start to overheat

Explain why a motor that is receiving too high of voltage would break

If the motor is receiving too high of voltage, it will burn out because its windings are not able to take on such high amounts of voltage. Thus the windings will burn out and the motor will overheat

What does UL stand for?

Underwriters laboratories- its a type of approval stamped onto compressor motors

This is the reserve horsepower a motor can operate at if need be for a limited amount of time

Service factor

A service factor for a motor of 1.35% means:

That the motor can operate for a limited time at 35% higher than its specified rating

What is the main determination behind the phases a motor receives?

Its application

T/F: Three phase motors cannot run on one phase power, but single phase motors can operate on two phases of three-phase power

True

What type of application would require an explosion proof motor?

May be used in a room that contains explosive gases. Normal motors with centrifugal starting switches might accidently ignite the gas and blow up the motor. Thus, an explosion-proof motor enclosed in housing can be used

What type of application would require a TECM (totally enclosed electronically commutated) motor?

TECM motors are used in applications where the area is very dirty. This keeps the motor protected from unusually high levels of gunk

What type of application would require a drip-proof motor?

Applications where there is a danger of water falling on and damaging the motor may use drip-proof motors

What does a motor’s insulation class signal?

The insulation class determines how hot the motor can safely operate in a particular ambient temperature situation

What are the two main types of bearings?

1. Sleeve


1. Ball

What two factors largely determine bearing selection?

1. Load characteristics


1. Noise level

This type of bearing is used when the load is light and noise must remain low, such as for a fan motor that is on a residential furnace

Sleeve bearing

Residential and light commercial applications normally see this type of bearing

Sleeve

What is the difference between oil ports and permanently lubricated bearings?

Oil ports require oil to be added into the bearings periodically by hand, while permanently lubricated bearings require no maintenance. Perminately lubricated are phasing out the oil port types

This type of bearing is a little louder and used with larger fans/pumps which are far enough away from the conditioned space that the noise will not be noticed

Ball bearings

While sleeve bearings use oil, ball bearings use:

grease

This is what determines how a motor will be secured during its operation:

its mounting characteristics

This type of mounting includes bolted metal to metal to the frame of the fan or pump and will transmit any motor noise into the piping/ductwork. Thus have louder sound “issues”.

Rigid-mount motors

This type of mounting uses different methods of isolating the motor and bearing noise from the metal framework of the system so as to make the motor less noisey than the rigid-mount

Resilient-mount motors

What are the four basic mounting styles:

1. Cradle mount

2. Rigid base mount

3. End mount

4. Belly-band mount

These are devices that connect the motor (driving device) to the driven load (fan)

Motor drives

What are the two main ways driving devices (motors) drive their loads?

1, Belts

2. Direct drive

What is the purpose of a motor drive?

The function of a motor drive is to transfer the motor’s rotating power (energy) to the driven device (the fan or other thing that needs to be powered)

What is the biggest pro to using a belt-drive motor drive?

The strength of the belt drive is its versatility. Both its pulley size and the speed of the driven device can be changed, which makes it very easy if the capacity of a compressor or a fan speed must be changed after the system has already been installed

What is this a picture of ?

A belt-drive motor