Features and Options

Resistive Elements
Wirewound

Wirewound resistive elements consists of an open helical stainless steel wire wrapped around a tubular porcelain core, allowing for fast and efficient cooling. In general wirewound resistive elements are ideal for low current conditions, offering excellent power dissipation, stable resistance, and shock-proofing.

wirewound-cutout-2

Edgewound

Edgewound resistive elements are strip type elements, essentially a stainless steel tape wound on tubular porcelain insulators. A rod is placed inside these resistive elements to form the resistive assembly. They are used in general for medium-level currents, touting shock-proofing, and compactness.

DSCN0507

Stamped Grid

Generally used for low resistance and high current, grid resistors are made with punched steel sheet with holes at in each end for mounting. Grids are then stacked on insulated steel rods. Mica washers are inserted between grids for insulation, and the rods are mounted between steel end frames. To obtain the best electrical connection, we weld grids together.

MegaResistors Stamped Grid Resistor

Enclosures
NEMA 1

Enclosures constructed for indoor use to provide a degree of protection to personnel against access to hazardous parts and to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt).

IP20
Protected against solid foreign objects of 12.5mm in diameter and greater. Not protected against water ingress.

MegaResistors NEMA 1

NEMA 3R

Dynamic Braking Resistor NEMA 3R

Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain , sleet, snow); and that will be undamaged by the external formation of ice on the enclosure.

IP23
Protected against solid foreign objects of 12.5mm in diameter and greater.
Water falling as a spray at any angle up to 60° from the vertical shall have no harmful effect.

Dynamic Braking Resistor NEMA 3R

NEMA 4

Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water); and that will be undamaged by the external formation of ice on the enclosure.

IP56
Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the satisfactory operation of the equipment; complete protection against contact.
Water projected in powerful jets (12.5mm nozzle) against the enclosure from any direction shall have no harmful effects.

MegaResistors NEMA 4

NEMA 4X

Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water); that provides an additional level of protection against corrosion; and that will be undamaged by the external formation of ice on the enclosure.

IP56
Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the satisfactory operation of the equipment; complete protection against contact.
Water projected in powerful jets (12.5mm nozzle) against the enclosure from any direction shall have no harmful effects.

MegaResistors NEMA 4

Enclosure Materials
Galvanized Steel

A protective coating of zinc is applied to steel. The zinc provides cathodic protection due to its greater negative electrochemical potential, making it the metal of preference to be consumed (when rusting). It often shows an aesthetic feature known as spangle, crystallites inside the coating. All of our galvanized steel material meets specific ASTM coating standards.

Once the galvanized steel is prepared, it is then treated for painting with a non-metallic iron phosphate coating. This heavily improves paint adhesion and increases corrosion protection if the metal’s paint film is broken. After the steel has been phosphatized, it is then powder coated. Powder coating cures in heat, forming a “skin”. This creates a harder finish, tougher than conventional paint.

Galvanized steel is a generally cost-effective and reliable material to prevent corrosion and damage to your product.

Galv Steel

Stainless Steel

The most widely used stainless steel is the “304” type, comprised of 18% chromium and 8% nickel. We also offer “316” grade stainless steel, comprised of 18% chromium and 10% nickel.

Stainless steel is touted for its resistance to corrosion and staining, and low maintenance needs. If your product will be used in an environment subject to corrosive conditions then we recommend using stainless steel over galvanized steel. The 304 grade steel provides greater resistance to corrosion than galvanized steel, and the 316 grade steel provides even more resistance than the 304.

Because stainless steel is comprised of chromium and nickel throughout the material itself, it provides corrosion resistance for a longer duration as it does not rely on a coating for protection. This leaves painting to be an an optional layer of protection. We generally use stainless steel with a natural finish unless otherwise specified.

If you need the high corrosion resistance paired with long-term usage, then consider stainless steel as a very viable alternative to galvanized steel.

SS

Anodized Aluminum

Anodizing is a process used to increase the thickness of a natural oxide layer formed on the surface of metal. Aluminum when exposed to any gas containing oxygen at room temperature will form a surface layer of amorphous aluminum oxide, which is very effective against corrosion.

We recommend anodized aluminum if you have specific corrosive conditions that are not or cannot be met by stainless steel. It is a very effective method of protecting against certain corrosive conditions.

anod alum

Other Optional Features
  • Normally open thermal switches
  • Junction box
culus

What are Dynamic Braking Resistors?

The purpose of a dynamic braking resistor is to slow down or to quickly stop a motor by draining excess voltage and keeping it within safe tolerances. Our rheostatic resistors dissipate the excess voltage as heat. This can help to lower the wear and tear of friction braking components, enable faster braking and eliminate the risk of a runaway due to overheating.

When removed from a power supply, most DC motors will act as electrical generators due to their permanent magnets. If a resistor is then connected as a load, the energy produced by the rotational inertia of the DC motor will be dissipated by the resistor slowing down the motor. While AC motors do not have permanent magnets in their rotors, they do have an induced magnetic field created by the rotating magnetic field in the stator. The energy lost in the stator will backfeed into the variable frequency drive (VFD), which will rise the voltage on the DC bus in the VFD. The greater the difference between the output of the VFD and the rotor’s actual speed, the more energy will be fed into the VFD. If the VFD tries to brake the motor too quickly, the voltage will rise too much and damage the VFD. Most VFDs will shut down as a safety feature before this happens, and the motor will coast to a stop by friction alone. With appropriately sized braking resistors the motor can be stopped much more quickly without raising the voltage to unsafe levels.

Braking resistors with smaller ohmic values will help motors stop faster but will also dissipate more heat. This will require the use of more mass in the resistor or a heat sink to keep its temperature within a safe limit.

Advantages

  • Faster braking of DC and AC motors.
  • Lower wear and tear of friction braking components.
  • Keep motor voltages within safe levels.
  • Eliminate risk of a runaway due to overheated friction brakes in some motors.
  • Reduce wasted time during braking.
  • Increase life of the equipment.
  • Improved service reliability.
  • Designed to absorb thermal expansions and contractions.

24 Month Guarantee

All of our products have a minimum 24 month guarantee. We are fully committed to ensuring your satisfaction.

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