On behalf of the company, we are currently undertaking a project for Terrapin Control system, a major client of this company, which was scheduled to last for 15 weeks. We have already covered 7 weeks, but the last four weeks have been marred by frequent power outages, consequently degrading most of our tests. As a result, we have found ourselves two days behind schedule, with no provision for additional time to see the project through, as each day spent past the prescribed deadline will see the company incur a $1,000 penalty.
To prevent future power outages from affecting and degrading our tests, we reckon that we need an alternative source of energy, which will automatically start up in the event of a power outage. Below are the available back up sources of energy which suffice the energy strength needed for the oven and the freezer in which our tests are conducted. Company analysts have narrowed down to two alternative sources of energy which would best serve our current needs. The strength specifications of the power supply for the oven should be 240 volts, 60Amp, while those of the freezer should be 120 volts, 40Amp. We need two backup systems, one for the freezer, and one for the oven.
Alternative power supplies
There is a broad division of alternative power supplies. The company analysts mandated us to make a choice among these energy sources: line-frequency also known as conventional power supply, switched-mode power supply, uninterruptible power supplies and on-machine power supplies. These are the devices best suited to addressing the problem at hand, but we have to pick one energy source for both devices. The electrical supply circuit selected must conform to all national and local electrical codes. We hereby analyze the available alternative energy sources before giving a recommendation on which one we expect the company to avail with us.
Uninterruptible Power Supplies
These are generally used to provide emergency power to a load in the event of the failure of the input power source, which in most cases is the mains power. It provides a near-instantaneous protection from input power outages by means of diesel generators. The runtime of most uninterruptible power supplies is less than 30 minutes, which can only allow the proper shutting down of the equipment. This is therefore not feasible for the project.
Line frequency/ convectional power supply
This is considered a relatively simple design meant to act as a medium for low DC power voltages. Should the line frequency power supply be faced with high current, it becomes increasingly bulky, and there ought to be the need to deploy large frequency transformers meant to synchronize the electronic regulation circuits. This power supply is sometimes referred to as linear. However, it has been termed as a misnomer due to the conversion of AC voltage to DC is non-linear (Basso, 2001).
The switched-mode power supply
This is a small, complex but very efficient power supply. This power supply sees the AC being directly rectified. The latter is then filtered in order to acquire a DC voltage. Essential to this study, it should be noted that switching occurs at extremely high voltages and frequencies ranging from 10 kHz-1MHz. In essence, there is the enablement of a technician to use transformers while filtering various capacitors of different sizes (Brown, 2010).
Such perspectives lead to advantages of using the switched-mode power supplies as opposed to linear frequency power supply. It is cheaper to install and maintain than the line frequency power supply.
On-Machine Power Supplies
These are resistant to harsh environmental conditions as they are vacuum encapsulated in potting material, a strategy that helps in providing resistance to shock, humidity, as well as vibration. They are used to minimize voltage drop in the event of a line loss. Their design allows them to be directly mounted on the machines with no enclosure required. They are, however, pretty unreliable in the event of power outages, therefore not feasible for the current project.
There was also the suggestion of the employing the services of an on-site technician who would be present at night rather than buying or leasing alternative energy sources, but it is imperative to note that the presence of a technician will not prevent a power loss, hence cannot prevent the degradation of the project.
From the analysis above, the switched mode power supply is preferred over the linear frequency power supply due to the safety measures associated with the system. Its advantages outnumber those of the linear frequency power supply. For instance, the switched mode power supply has a feature known as crowbar circuit which protects all users from harm. It also protects the device from short circuits, if there should be abnormal power detections.
The Costs Involved
This involves a direct choice between buying completely new equipment and leasing power supply equipment. Although it is cheaper than the linear frequency power supply, the switched mode system is by all means expensive to install and maintain, considering the fact that it may no longer be needed after the completion of the current project. Leasing the system for a period of eight weeks would be more feasible for the company in the long run. The cost of buying a new switched mode power supply system runs up to $46,400, without installation and maintenance costs while the monthly cost of leasing the system is slightly below the $15,000 mark. Since it is needed for just eight weeks, which adds up to two months, the cost of leasing will approximate to $30,000. This is $16,600 less than the cost of buying a new system. Leasing the system, therefore, is more economical than buying one.
It is hoped that this system will be availed to our engineers on the ground to ensure timely completion of the project, while avoiding unnecessary fines to the company. A lot of consideration has been put to all the listed alternative sources, plus many others, before the switch-mode power supply system was picked. The provision of this device will enable the team to continue with the experiments, which will warrant the timely completion of the project, which will enhance the company’s corporate image. Thank you in advance.
Basso, C. P. (2001). Switch-Mode Power Supply Spice Cookbook. Washington: McGraw-Hill Professional.
Brown, M. (2010). Power Supplies Cookbook. Phoenix: Newnes.