Once the heat inside the cabinet reaches critical temperatures for the components, component failure results.

One way to cool a cabinet is by electrical fans. Another is air conditioning…yes, that’s right. Your control panel might be air conditioned while you sweat your …. off in the maintenance office.

One more way is through venturi cooling, and information from one of the companies that provides those products is right here.

And, if you are in need of a custom control panel, built to your drawings, or if you need one designed and built from scratch, check this out.

Like yourself, I wander around the blog world too, and occasionally find a site that complements this one very well.

I found a site that does that…providing the visitor with a lot of information about electric motors.

Under “Types of Motors” Sawdustmaking.com offers this info.

This motor is used where stops and starts are somewhat frequent. Common applications of split phase motors include: fans, blowers, office machines and tools such as small saws or drill presses where the load is applied after the motor has obtained its operating speed.

Capacitor Start

This motor has a capacitor in series with a starting winding and provides more than double the starting torque with one third less starting current than the split phase motor. Because of this improved starting ability, the capacitor start motor is used for loads which are hard to start. It has good efficiency and requires starting currents of approximately five times full load current. The capacitor and starting windings are disconnected from the circuit by an automatic switch when the motor reaches about 75% of its rated full load speed.

Uses

Common uses include: compressors, pumps, machine tools, air conditioners, conveyors, blowers, fans and other hard to start applications.

If you want more information from their site on electric motors, please click here.

And to get your electric panel questions answered, and a quotation on a custom control panel if you wish, please click here.

The signal to or from the PLC can be in many forms . The typical signal would be 4-20MA (could also be 0-20MA, 0-10VDC). Other examples would be an RTD, a thermocouple, millivolts, etc.

When this signal is an input to a PLC it would be used to monitor devices in the field, such as a flow meter, a pressure transducer, level transmitters, feed back from drives, or any other of the many devices used to measure a process.

When the signal is an output from a PLC it would be used to give a speed reference to a device in the field, such as an inverter or dc drive, a positioning control, regulating valve or any other device that can accept an analog signal as a input to control it.

Analog signals are usually used in a PLC with a PID loop which is a closed loop control.

A typical example of a PID closed loop control would be an input to the PLC from a flow meter and an output from the PLC to an ac drive. The operator or PLC programmer would have entered a set point for the flow into the PLC program. The PLC will compare the flow measurement from the flow meter with the set point and depending upon whether the flow is above or below the set point, will increase or decrease the signal to the drive. The drive in this case is activating a pump and the increase or decrease in signal will result in and increasing or decreasing of flow to bring it closer to the desired flow rate. The further the input is from the set point, the greater the change in output will be.

More about PID loops in another discussion. If you need help with any control challenges, why not ASK JIM?

PLC is the acronym for Programmable Logic Controller. Okay, we can see where the PLC comes from, but then what is a programmable logic controller?

A PLC is a computer similar in concept to, but different from, a desk top or laptop computer. It has internal programs, data storage and input devices like the desktop or laptop computer, but it provides more capabilities than just those basic computers.

The PLC will have the ability to accept incoming information from a variety of devices on a piece of machinery, not just from the mouse or keyboard found on the home computer. The incoming information might be from push buttons, timers, toggle switches, proximity switches; the incoming signal can be from many different sources and these sources can feed information to the PLC through the PLC’s Inputs.

Once the PLC receives an input from somewhere, it executes the control program that has been programmed into it by the PLC programmer. This program then may create an output signal of some sort.

The Outputs are part of the PLC as well, and allow a broad range of equipment to be connected to them. As the CPU executes the program, it will send information to the correct PLC Output (if it’s been programmed correctly), and that output signal will then cause some other external device on the machine to function.

Even though the PLC has a central CPU (central processing unit) just like the home computer, it differs by having more than just two inputs (mouse & keyboard), and it differs by being able to send control commands out from itself to initiate action somewhere else on a machine.

PLC’s are often quite small (in comparison to their P.C. cousins) though those with large numbers of Inputs or Outputs (I.O. points) can get quite large. They are installed inside of a control panel enclosure on or near the machine they control. Wires leading from the various Input devices to the PLC, and those from the Output’s of the PLC, enter or exit the enclosure through holes drilled in the enclosure wall.

Control panel enclosures can be made of aluminum, mild steel, stainless steel or fiberglass.

For more information on the various materials, and the gaskets commonly used for seals, please click here and follow the links to Rantro Tips.

We’ve been reviewing the specifications of the various NEMA ratings in this series of blogs, and this is the last, where we’ll review ratings 6-13.

If you need more information about machine control panels and accessories, why not Ask Jim?

NEMA 6

NEMA 6 enclosures have to be constructed for use either indoors or out, must provide a degree of protection against persons accidentally being able to come in contact with equipment inside the pane. NEMA 6 also means the panel will provide protection against falling dirt, hose-directed water, and will prevent the entry of water into the panel should it be temporarily submerged at a limited depth. Contents and the panel must remain undamaged by the build up of external ice on the panel enclosure.

NEMA 6P

All the same conditions as NEMA 6, but this panel must prevent the ingress of water if the panel has a prolonged submersion at a limited depth.

NEMA 7

A NEMA 7 enclosure is used indoors in locations with classifications as Class I, Groups A,B,C, or D, and shall be capable of withstanding the pressures resulting from the internal explosion of specified gases, and must contain such explosion sufficiently that an explosive gas-air mixture existing in the atmosphere surrounding the panel enclosure will not be ignited. Any enclosed heat generating devices shall not cause external surfaces of the panel enclosure to reach temperatures capable of igniting gas-air mixtures in the surrounding atmosphere. NEMA 7 enlcosures shall meet explosion, hydro-static and temperature design tests.

NEMA 9

The are panel enclosurs intended for use indoors, in locations classified as Class II, Groups E, F, or G, and shall be prevent the entrance of dust. Any enclosed heat generating devices shall not cause external surfaces of the panel enclosure to reach temperatures capable of igniting or discoloring dust on the surface of the enclosure, or igniting dust-air mixtures in the surrounding atmosphere. Enclosures must meet dust penetration, temperature design tests, and aging of gaskets if used.

NEMA 12

These are enclosures construction (without knockouts) to be used indoors, and to provide a degree of protection to persons from incidental contact with enclosed equipment. They must also provide a degree of protection against falling dirt, circulating dust, against lint fibers, and dripping or splashing of liquids.

NEMA 12K

Offers all the same protections as NEMA 12, these enlcosures have knockouts.

And last but not least….

NEMA 13

These are enclosures for indoor use, and to provide a degree of protection to persons from incidental contact with enclosed equipment. They must also provide a degree of protection against falling dirt, circulating dust, against lint fibers, and against the spraying, splashing, and seepage of water, oil and non-corrosive coolants.

In our continuing blogs about NEMA ratings for electrical enclosures, today we’ll look at the NEMA 4 and 5 ratings. NEMA rates panels on a scale of specification numbered 1 through 13, with numbers 1, 4 and 12 normally used for panels.

NEMA 4

To be classified as a NEMA 4 panel, the enclosure must be constructed for either indoor or outdoor use, to provide a degree of protection to prevent incidental contact to enclosed equipment by any personnel, to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, and splashing or hose directed water. The enclosure must remain undamaged by the external formation of ice on it. NEMA 4 panels are normally constructed of painted carbon steel.

NEMA 4X

To be classified as NEMA 4X, the panel must provide all the protection as noted in NEMA 4, as well as provide protection of the panel enclosure itself from corrosion. NEMA 4X panels will normally be constructed of stainless steel, or fiberglass.

NEMA 5

A NEMA 5 classified panel provides a degree of protection to personnel against incidental contact with the enclosed equipment, and to provide a degree of protection against falling dirt, settling airborne dust, lint, fibers, and dripping or splashing of liquids.

Need more information about machine control panels? Click here.

We use a NEMA rating to identify the particular protection level of Machine Control Panel Enclosures.

NEMA ratings for control panel enclosures number 1 through 13 although the common ratings for enclosures are NEMA 1, 4 and 12. In this blog we will review the various control panel enclosure ratings.

NEMA 1
This is the lowest NEMA protection rating for a control panel enclosure. In order for the panel box to be considered as NEMA 1, it must provide a basic level of protection from persons coming into incidental contact with the contents of the panel box, and it must provide protection from the panel box contents being exposed to incidental contact with falling dirt.

Panels with NEMA 1 rating are general purpose because they lack gaskets. They should only be used indoors in a dry location.

NEMA 2
A panel with NEMA 2 rating must provide the protection as outlined under the NEMA 1 standard as shown just above, as well as providing protection for the panel contents from dripping or splashing liquids.

When electric motors are operated they generate heat. Some motors generate lots of heat (probably those that don’t show the motor efficiency on the plate) and some less so.

Heat generation by the motor indicates a of loss of energy, as the electricity is being used to generate heat rather than rotation. The more heat the motor generates, the less efficient it is in turning electricity into rotary motion.

Motors with higher efficiency ratings likely have more metal in their construction. Insulated metal is placed between the laminations to reduce eddy currents that produce energy wasting heat.

If you have an efficiency rating on the motor data plate of your motor, you will see a rating in percent, as in 86%, or you might see it as a decimal, as in .86.

When purchasing a motor, higher efficiency motors will reduce operating costs.