In this part we will provide information on some good habits that should have maintenance personnel to accomplish their work satisfactorily.
Why wear out the brushes on a DC motor?
The use of carbon brushes is the result of mechanical friction and electrical erosion. Friction produces carbon dust, the result of electrical erosion is the vaporization of carbon with a small physical residue.
Friction: Coal and copper bar has a high coefficient of friction. For the friction coefficient is small, the switch must have a good movie.
Erosion: This may be the result of improper film on the switch.
What is a good movie to switch?
When electric current passes through the coal and copper bar in the presence of water vapor, forming a microscopic layer or film around the switch. A good movie is dark brown, bronze or brown burnt chocolate. Consult with a color chart switch to know the condition of your switch.
What if I want to install an AC motor drive after ...
a) stored for a period of less than 1 year?
It needs no modification or special test.
b) stored for a period between 1 to 2 years?
Apply power to drive an hour before giving the command boot (charging time 1 hour).
c) stored for a period between 2 to 3 years?
Using an AC power source. Apply 25% of the input voltage for 30 minutes. Increasing the voltage to 50% for 30 minutes. Increase to 75% strain for 30 minutes.
Increase the voltage to 100% for 30 minutes. The converter is ready for operation (charging time 2 hours).
d) stored for a period of 3 more years?
Proceed as above but the periods must be 2 hours (8 hours charge time).
Physical location of the drive
The location of 19H control is very important. Be installed in a place protected from direct exposure to sunlight, corrosives, harmful gases or liquids, dust, metallic particles and vibration. Exposure to these elements may reduce shelf life and degrade the control performance.
There are several other factors should be carefully evaluated when selecting the installation site:
1. To be effective in cooling (heat dissipation) and the maintenance, control must be mounted vertically on a flat vertical surface, smooth and non-flammable. When the control is mounted in a cabinet, use the information provided watts loss in Table 2-1 so as to provide cooling and ventilation (4 watts per amp continuous output).
2. To permit proper air circulation, you should leave a gap of 5 cm (two inches) or more around the control.
3. Front access must be provided to open the control cover or remove it to make service and to allow viewing the display (LCD) on the keyboard. (The keypad may optionally, be mounted remotely from a distance of 30 meters [100 feet] of control).
Controls that are installed in a cabinet mounted on the floor leaving room should be located to open the cabinet door. This space will also have enough air circulation for cooling.
4. Reduced capacity for altitude. Up to 1 000 meters (3300 feet) are not required reduction. More than 1 000 meters, reduce the current and peak output by 2% per 305 m (1 000 feet).
5. Temperature derating. Temperature reduction in capacity. Up to 40 ° C are not required reduction. Over 40 ° C, reduce the current and peak output by 2% per ° C. The maximum temperature is 55 ° C.
