Monthly Archives: July 2018

How Are Bus Plugs and Ducts Used in Manufacturing?

All buildings whether commercial or residential require some sort of electrical power in order to provide lighting, outlets and other electrical devices. For commercial buildings, you have power needs for machinery, lighting, cooling systems, and other types of electrical needs. Typically, in a residential building, you have electrical service entering the house with cables. This is different then how electrical power is distributed in commercial and manufacturing settings.

Commercial buildings, especially those used by medium or large-scale manufacturing businesses use a larger type power distribution system that requires a much different way to run power through the manufacturing spaces of the building. Unlike residential power distribution which uses cables to carry the power throughout the home, commercial building use bus ducts or sheet metal runs with either aluminum or copper busbars.

History of the Busway Power Distribution System

The busway and bus bars were first introduced in the US back in the 1920’s at the request of the auto industry in Detroit, Michigan. The system gave them the necessary versatility that was needed for supplying power to the assembly line equipment that was being used in the manufacturing facilities at the time. Over the years since, there have been numerous innovations that have improved on the original design and installation procedures.

 

Commercial Power Distribution System Components

Heavy duty machinery typically found in manufacturing plants have unique power requirements which cannot be served by typical power distribution systems that are found in most residential homes and most commercial buildings. For these unique power requirements, there is a power system that is designed especially suited for this type of need. Bus Ducts and Bus Plugs are combined to deliver the necessary power to each machine

 

Bus Ducts – Bus Ducts also referred to as busways are sections of sheet metal with bars attached to them that are made of either aluminum or copper.  The sections are connected together in order to reach each piece of machinery that is needing the power. This type of power distribution system requires trained, certified professional electricians to install them and ensure that they are in full operation at all times.

 

Bus Plugs – Bus Plugs are specially designed components that work in tandem with the busbars in a unique type of power distribution system that is typically installed in a large-scale manufacturing facility. Each bus plug is used to connect directly to busways that are running throughout building to deliver the power to equipment like large motor starters and other power switching equipment.

Indoors and Outdoors Power System

One of the benefits of using this type of system in a manufacturing facility is that it can be used both indoors and outdoors to deliver the necessary power to different parts of any operation. The unique design of the system helps to prevent voltage drops across each of the numerous sections of the bus ducting throughout the building.

 

The system can also be fitted with a trolley system that is designed to deliver power to equipment that is designed to move frequently. There are also cables that are used to deliver the power directly to the trolley itself.

 

Learn more about J & P Electrical Company and their vast line of new, surplus, and refurbished industrial electrical components including: circuit breakers, bus ducts, bus plugs, disconnects, fuses, panel switches, tap boxes, and transformers at www.jpelectricalcompany.com.  To contact one of our product reconditioning specialists, call 877.844.5514 today.

Power supply ins and outs

While the switching power supply data sheet may document compliance to over two dozen general specifications, focusing on the input and output specifications and the safety standards that impact installation highlights some of the basics of specifying and integrating the device.

Most power supplies have the input voltage well supported with a nominal range of 85-264 Vac suitable for use with any 115- to 230-Vac supply. The typical voltage frequency range covers any 50- or 60-Hz supplies, as well.

From an integration standpoint, things start getting interesting when discussing nominal current and inrush current. It is common for the input to most power supplies to be internally fused, but adding supplementary fusing or, preferably, a miniature circuit breaker (MCB) to the input that can be turned off and on is best practice. The full load input current is noted in the data sheet and fusing between 150% to 500% of the specification, and wiring with suitable gauge wire, is appropriate. For example, when wiring 2 A to 10 A switching dc power supply, include a 10 slow-blow fuse or MCB and 16 AWG wire to protect input wiring.

From an integration standpoint, things start getting interesting when discussing nominal current and inrush current.

However, be certain that the fuse or MCB can handle the inrush current. While the inrush duration is less than half an ac cycle, it can be six to 20 times the full load input current. This can certainly trip fast-blow current protection devices, so check the manufacturer’s recommendations as slow-blow fuses and circuit breakers are likely needed.

The power supply output voltage and the nominal output current or maximum output power are likely the most important specification for the application, but there is more. From the voltage side, there is output adjustable range, overvoltage protection, voltage tolerance and ripple to consider. These output-voltage specifications can impact sensitive applications, such as analog circuits or test systems, but most 24 Vdc power supplies can deliver the needed potential.

The output current may need a closer look—specifically, nominal output current and current limit method. This includes protection against short circuit and overload. This power-supply output protection often resides internally to the device, but that doesn’t mean additional protection is not needed when integrating it.

Short-circuit protection is often built-in to the power supply and will shut off output power when a short circuit fault occurs. The input power typically will need to be cycle off to on to reset this fault.

Many power supplies use a feed-forward current limit method on the output. This limits the maximum overload current to 110%, 150% or 200% of nominal current, depending on the power supply selected. With this method and when an overload condition occurs, the current continues to rise to the limit, but the voltage drops to maintain constant power. This disrupts the constant voltage feature of a power supply but can help to start an electric motor with high inrush or power through other high-inrush events.

These feed-forward current limit events may cause devices, such as cameras, light curtain controllers or safety relays, to intermittently lose power. The switching power supplies’ built-in protection from overload can also affect the output protection methods required. Adding fuses, MCBs or electronic-circuit-protection (ECP) devices to the output circuit can help to capture and isolate the circuit causing the overcurrent by tripping the protection device.

Translated to design considerations, that means to separate high-inrush dc circuits, such as motors, from low-level circuits, such as controllers, HMIs and safety relays. Distribute the dc power output through multiple protection devices such as fast-blow, non-time-delay or slow-blow circuit breakers depending on the connected load. For even better detection of overcurrent faults, the ECP monitors both current and voltage. A prolonged undervoltage condition can help to indicate the circuit causing the problem.

Designing the dc power distribution to feed power through multiple protection devices also enables the use of smaller gauge wire. The use of smaller wire is common in discrete and analog I/O and other signal cable runs.

The discussion above regarding output short circuit and overload is related to general safety specification, met by many power supplies, for Protection Class 1 (IEC 536 or NFPA 70, Article 725). While Article 725 does cover some low-voltage industrial control, some computer networks and other remote-control, signaling and power-limited circuits, it’s as much about usage and power limitations that differentiate it from power circuits.

Class 1 discusses the portion of wiring in the power-supply circuit between the overcurrent device and the connected equipment. Class 1 circuits have a voltage requirement of less than 30 V and a power restriction of less than 168% of the device’s Volt-Amp rating, and overcurrent protection is required.

Some power supplies meet Class 2 requirements—upgraded output protection for the connected loads. This class focuses on the circuit between the Class 2 power supply and the connected equipment. It protects the circuit from fire and the personnel from electrical shock.

There are many requirements for Class 2 circuits, but wiring to the power-supply load side does not require a fuse if the proper wire is used. An example of this is power over Ethernet (PoE) cables. Without proper current limiting and wire size, 100 cables together in a bundle could cause quite a fire.

Original Source: https://www.controldesign.com/articles/2018/power-supply-ins-and-outs/

Original Author:  Dave Perkon, technical editor

Fused Disconnect Switch vs Circuit Breakers

For all those people who are looking for major differences between fused disconnect switches and circuit breakers, this post will eradicate all your confusions and help you to make the best choice. Before proceeding further, let’s shed some light on why you need devices such as circuit breaker panels and fused disconnect switches.

Electrical circuits in residential and commercial establishments are designed to carry a certain amount of current. Due to any reason, if more current passes through them, it can lead to dire circumstances where sensitive appliances and equipment can be destroyed. In some situations, this overflow of current through electrical circuits can also result in a fire that can prove to be extremely fatal for the inmates of the building.

In order to prevent such a situation from happening, different devises such are used that serve the purpose of protecting overcurrent in wires. These devices, in a current overflow situation, disconnect or open the circuit. This helps in preventing the fire from erupting. Thus, there are fewer chances of any damage to be caused to appliances and equipment installed in the building. Devices such as circuit breaker and fused disconnect switch also work in case of short-circuit situations.

Now that you are aware of the basic function of both these devices; let’s now have a look at major differences between them.

Fused Disconnect Switch

A fused disconnect switch, as the name suggests, is a combination of a fuse and switch. The fuse shuts the circuit off and switch disconnects it in case of an issue. Switches are designed to be shut the power off manually. On the other hand, fuse works in the opposite way. They are made up of a small filament that melt down in case of a current overflow. A fuse’s current rating is preset. Thus, when the current exceeds the rating of the fuse for a longer period of time it melts automatically. As a result, the circuit is disconnected.

A point to note here is that when a fuse disconnects the circuit, it can be used again. Power can only be restored if the fuse is replaced by a new one.

Circuit Breaker

With circuit breaker, there is no issue of getting a new fuse every time it turns the power off due to the overflow of current or short-circuit. Thus, it is often considered a better option for many appliances. Circuit breaker panels can also be turned off in a manual way as they also serve the functions of a switch. This feature makes them handy if you want to do get some electrical work done in the building.

A circuit breaker disconnects the circuit automatically with the help of an electromagnet it features when it detects overflow of current or a short-circuit. After the problems have been fixed, it only needs to be turned back on for restoring power.

A Final Word

To sum it up, both these devices can help a great deal to eliminate issues caused by the overflow of current or short-circuit. As stated above, a circuit breaker disconnects the circuit both automatically and manually and a fused disconnect switch offers the same purpose. The difference lies in their design and functionality. Thus, when selecting them, take into consideration the electrical requirements of your premises for taking the best decision.

Learn more about J & P Electrical Company and their vast line of new, surplus, and refurbished industrial electrical components including: circuit breakers, bus ducts, bus plugs, disconnects, fuses, panel switches, tap boxes, and transformers at www.jpelectricalcompany.com.  To contact one of our product reconditioning specialists, call 877.844.5514 today.