How to Select a rectifier for a telecom power system?

The overall elements you should pay attention to are cooling,operating temperature, electrical parameters, and system connectivity. Let's talk about it one by one.
 

Cooling Methods

The cooling method employed in the telecommunications power system is perhaps the most critical consideration in choosing a rectifier. In fact, the choice of cooling regime can affect the rectifier's physical size by a factor of up to 2.5.

Fan cooling and convection cooling are the main methods used to cool a rectifier. Telecom systems have traditionally favored convection cooling for its low maintenance cost and long product life compared to that of fans, which add cost and impose noise and space penalties.

However, a poorly designed enclosure using convection-cooled rectifiers can result in a system that is much more unreliable than a system using fan-cooled rectifiers. Hot spots in convection-cooled systems can be difficult to avoid. A convection-cooled rectifier requires an efficient enclosure design to achieve optimal cooling. Critical semiconductors in fan-cooled products can be more reliable because they exhibit lower temperature rises than in comparable convection-cooled systems.

New rectifiers have alarm and control features that can monitor fan performance and allow the rectifiers to be easily replaced in the field. Thus, fan-cooled rectifiers can be reliably maintained in a cost-effective manner.

Input voltage

Another critical factor in rectifier selection is the input voltage range. Designers now often specify input ranges to suit world voltage ranges of 85 to 264 V or more. In practice, for most applications, neither end of the voltage range is optimum. Providing full parametric performance over a wide input voltage range can significantly increase the rectifier's cost and size, as well as increase the amount of cooling required.

Some applications require rectifiers to operate fully over wide input voltage ranges. However, other applications require only short-term capability for input voltages below a threshold level. Thus, careful selection of input voltage range can eliminate the need to manage the power dissipation on a continuous basis, resulting in substantial cost and size savings.

Temperature range

Another key consideration when selecting a rectifier is the operating temperature range of the telecom equipment. To minimize cost and maximize a power system's capability, the designer must look closely at the temperature extremes and determine if full performance is required.

More specifically, some equipment may require continuous low-temperature operation without any performance compromises, in which case the power system must be fully rated and meet all parameters. But in other applications where low-temperature operation is required only briefly, the user can save costs by specifying the rectifier to start up at the lowest required temperature and fully meet all parametric requirements at a higher temperature.

Signal requirements

With the right thermal management and monitoring features within a rectifier it is possible to automatically offer more power at lower temperatures. Otherwise, the rectifier's output capability would be restricted to the safe power level that can be sustained at the maximum ambient temperature.

Thus, alarm signals and other control features should be factored into the rectifier selection. Sometimes only an output-healthy/rectifier-fail alarm signal is needed, but other times the rectifier must incorporate a very sophisticated signal package, with or without local displays.

Rectifiers with intelligent signal packages give the end user easily programmable options such as output current signal, current-limit programming, forced-current share, and battery temperature compensation. A low-voltage-disconnect module inside a rectifier is another enhancement for some medium-power applications. This module prevents permanent battery damage when the power mains fail and the battery voltage falls below a threshold level.

System Connectivity

Another issue to consider is the way that a rectifier is connected to a system. The three ports that need to be connected are the ac input, dc output, and alarm signals. 

Basic rectifiers can have a screw terminal for the power connections and a simple multipin signal connector, but these are becoming unpopular because they are relatively difficult to install or replace. While a popular alternative is a hot-plug rectifier. This unit can be automatically connected to the ac supply, the dc bus, and alarms monitoring circuits as the product is slid on to its support shelf. Installation or removal requires no real skill.

Hot-plug rectifiers cost more to produce than more basic products with screw terminal connections. However, if the cost of installation and maintenance is taken into account, they can be more cost effective than basic rectifiers.

Other rectifiers that fall in between the basic and the hot-plug types are also available. A unit with an input connector, output connector, and signal connector that does not automatically make connections as it is installed on a shelf can still be hot swapped. However, this process requires greater skill to ensure that the system integrity is maintained during the process of changing or installing a rectifier.

The right choice of connectivity for a rectifier depends greatly on the application and location. Hot-plug rectifiers are preferable in a remote location and where installation or maintenance has to be done without a skilled worker. Where skilled technicians are available, a more basic rectifier may be more suitable.

KELINGYIZHI Communication Technology are trying efferts to supply customers with high performance rectifier modules and provide more reliable telecom power systems to worldwide. Rectifier module from well-known brands like Huawei, ZTE, Vertiv and Eltek. We sincerely provide before&after sale services to every customer, if you still need help on how to select rectifiers for telecom power supply system, feel free to contact us!