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Marathon Electric Generator Review

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For over 60 years, people have known that Marathon means reliable power.

If you need a backup power system in case of an emergency or high-performance generators to power your daily operations, Marathon Generators has you covered. In addition, they provide guarantees on all of their products.

Their extensive line of industrial generators, with outputs ranging from 5 kilowatts to 4000 kilowatts, is built to last and tailored to meet the specific requirements of your business.

Marathon Generator has helpful people on hand to answer questions and provide assistance with any issues that may arise with their products.

Marathon Electric is an affiliate of the Regal Rexnord group. The Regal Rexnord Corporation is a world-renowned manufacturer of mechanical and electrical motion control and power generating devices.

Regal Rexnord, which is headquartered in Beloit, Wisconsin, also has locations in Mexico, Europe, and Asia where it produces and sells products and provides services.

Marathon Electric Generator Review

Harsh Duty Generators - 10 watts to 800 watts, 60 and 50 Hz

These sturdy gadgets can hold up against anything, from the humid, salty air of the sea to the scorching, dry, dusty conditions of a mining operation.

With reinforced windings, fully enclosed exciter stators, and heavy-duty rectifier assemblies, Marathon's Harsh-Duty alternators provide dependable performance with minimal upkeep.

Places these generators can be used:

  • Quarry and aggregate pits
  • Mining
  • Barges
  • Chemical plants
  • Huge factories 
  • For any request within fifty miles of the coast
  • Buildings and locations for lease
  • Moviemaking as an industry
  • Work in the Oil and Gas Fields
  • Refineries, related to agriculture and water systems
  • Houses and other buildings that are located in remote places.

Harsh Duty Exciter

Their expertise lies in producing heavy-duty exciter stator motors. To protect the winding and jumper sleeve ends, fiberglass tape is toroidally wrapped around the coils. Sleeves are rolled up on every coil to coil jumper.

The windings are then thoroughly submerged in varnish to provide a tight seal. All of the exciter stator is then varnished with a two-component, anti-tracking top coat finish to ensure the highest possible level of protection against harsh, high-humidity conditions.

Main Stator Winding Strength

Multiple cycles of dipping and baking in 100% solid varnish are performed on the primary stator windings. The primary stator is then given the ultimate in protection from the harsh marine environment by being coated in a two-component, anti-tracking top coat finish varnish.

Wet Winding

Since 100% uptime is critical in industrial applications, Harsh Duty® Generators employ single-piece laminations and wet layer winding processes to create the most reliable rotor structure available.

Rectifier Assembly

Harsh duty generators are commonly used in parallel Make-Before-Break-Transfers, strong motor starting loads, and extremely non-linear loads. With diodes chosen with ratings of 300% above worst case design requirements, Marathon® Generator's high duty rectifier assemblies are built to handle harsh voltage transient surges and over-current circumstances. For ultimate environmental protection, diodes are welded case stud type and hermetically sealed.

Selenium surge suppressors come standard on all 360 and larger framed versions. Selenium suppressors have a heat-sink capacity up to 40 times greater than that of a Metal Oxide Varistor, making them an excellent choice for protecting diodes under high loads (MOV).

Support Systems

If PMG excitation support is required, one of two voltage regulators that are PMG-ready can be installed on a HARSH DUTY generator. The isolated PMG power supply is used in conjunction with the tried and reliable Digital Voltage Regulator (DVR) to regulate the voltage by 14%, allowing for maximum motor starting capability and consistent voltage output independent of the generator's load.

The DVR offers 300% short-circuit support to provide a long, dependable service life and 14 different security mechanisms, several of which may be adapted to your specific application. The PM500 is an advanced voltage regulator and generator protector that is both analogue and robust. The PM500 is a powerful yet easy-to-use analogue controller with enhanced full-wave dynamic performance, maximum motor starting capabilities, 300% short circuit support, and six independent protective features. It also has voltage regulation of 14%.

Top of the Range Insulation

Popular insulation solutions are designed to operate in these types of controlled environments. There is often a lot of moisture, dust, sand, grit, or other airborne pollutants in a factory. Because of the extreme conditions present in industrial settings, the useful life of a standard insulating system may be drastically reduced.

Marathon Generator Guide

The generators used in marathons are synchronous AC generators that are brushless, self-excited, and include an external voltage regulator.

The six essential components of a generator are the main stator (armature), main rotor (field), exciter stator (field), exciter rotor (armature), rectifier assembly, and voltage regulator. Keep in mind the following to make sense of the aforementioned terminology:

The field provides the direct current (DC) power, the rotor spins, the armature generates alternating current (AC), and the stators don't move. 

An exciter is the moving part of a generator that produces an electromagnetic field to excite the armature, which is rotating. It is expected that the static field will be the primary source of residual magnetism in the generator (exciter stator).

Even when the exciter stator (field) is not electrified, the exciter rotor (armature) can still create AC voltage thanks to the remaining magnetism. The revolving rectifier assembly converts this AC power to DC and supplies the main rotor with it.

The main rotor (field) induces a voltage into the main stator of the generator as the shaft of the generator continues to rotate (armature) (armature). The automatic voltage regulator can run at rated speed thanks to the voltage created by the main stator's main stator by the exciter's residual magnetism.

When the regulator supplies power to the exciter field, the terminal voltage of the generator rises. This residual magnetism technology eliminates the need for the regulator's special field flashing circuit.

Once the generator has established the initial residual voltage, the regulator will supply a controlled DC field voltage to the exciter stator, resulting in a regulated terminal voltage from the generator.

Start-up

Here's what you need to do to get the generator set up and running for the first time.

The load must be unplugged from the generator output. Either the primary circuit breaker or the fused disconnect must be in the "open" setting.

Second, activate the power supply for the automated voltage regulator. Remove the fuse or disconnect and insulate one of the power wires leading to the regulator.

Third, verify that the primary mover was started in accordance with the manual's directions.

If the flat contains space heaters, check sure they are switched off. Some setups have the main circuit breaker or transfer switch's auxiliary contacts automatically activate the space heater circuit when the generator is connected to the load.

Set the proper speed after the main mover has been started. Check the generator's label to see what it's called.

This first test is meant to discover any wiring issues without putting the gadget in danger by using the regulator. The voltage between each line and the neutral must be equal. If the voltages are stable, turn off the set and reattach the regulator.

If the voltages are not stable, turn off the equipment and check the connections. Consult the factory if the issue continues to exist. There should be between 10 and 25 percent of the original voltage present after turning off the regulator.

It's recommended to keep track of the residual voltage and driver RPM in order to use them as a reference point in case of future problems.

Power on the generator and adjust the terminal voltage using the regulator voltage. If the regulator allows for fine-tuning of the stability, do so as directed.

Check the balance of all line-to-line and line-to-neutral voltages once more. For future reference, it is recommended to record the generator's terminal voltage, driver speed, and no load excitation (DC voltage to the exciter stator).

Turning off the main breaker will stop the load.

Watch the generator's output current to make sure it doesn't go above the nameplate rating.

Examine the generator's frequency (speed) under load. Modify as needed.

Shutdown Procedure

There are no hard and fast rules on when to turn off the generator, but certain best practices can extend the life of the machine.

It is recommended that all loads be disconnected prior to shutdown (open the main circuit breaker or use a disconnect). This is especially important if loads can be damaged by low voltage or low frequency during generator "coast down."

To prevent any voltage from being applied to the generator when it is at rest, it is necessary to remove all sources of power. Failure to comply may result in injury to workers or damage to equipment.

Thirdly, if the system includes built-in heaters, the heater circuit should be activated.

Maintenance

The following steps should be followed for routine equipment maintenance to ensure a long service life and reliable operation. The frequency of servicing will be based on the conditions under which the machine is being used.

Make sure the intake and exhaust air screens are always clean and debris-free. A decrease in cooling air flow and an increase in operating temperatures are the results of a clogged intake air screen. The lifespan of the generator will be shortened and it may be damaged if this continues.

Secondly, all Marathon generators come equipped with double shielded ball bearings that are permanently oiled. After every thousand hours, be sure to check the bearing(s) to ensure they are running smoothly and quietly. If you have a generator that runs nonstop, you should swap the bearing every time you have a major engine service.

Conduct routine inspections to determine if any pollutants have settled inside the windings (such as dirt, grease, etc.). If the machine's winding components have been badly soiled with oil and grime, it should be taken apart and cleaned thoroughly.

The generator should only be cleaned and dried by a professional service center because only they have the right equipment and chemicals for the job. 

Check the DC no load excitation voltage once every 2,000 hours or in combination with regular engine maintenance. Check this reading against the one taken right after powering up.

Problems with the exciter, main field, or rotating rectifier assembly could be to blame if the excitation voltage is much higher than the reference value when the load is removed. Make that the RPM is consistent with the first evaluation.

Monitor insulation resistance using a 500-volt mega-ohm meter. The minimum acceptable reading is two megaohms. When the reading drops below the threshold, it's time to get the generator serviced by a professional.

Service

The methods of repair outlined in this section can be performed on-site with only a few commonplace items. All service procedures should be carried out by trained maintenance personnel. Spare components can be purchased directly from the manufacturer or through a certified service center.

Field Flashing

Restoring the generator's magnetism requires connecting a 12-volt battery to the exciter field and running it as described below.

Disable the power source first. The F+ and F leads of the exciter field must be removed from the regulator.

Secondly, connect the battery's positive and negative terminals using the F+ and F- leads, respectively. To achieve this, you can use a length of lead wire to unplug the battery from its terminal (batteries may explode when exposed to an electric arc).

After 3–5 seconds, disconnect the F– lead. The result should be an inductive arc. You should try drawing the arc again if you don't see any results.

Third, link the F+ and F- leads back to the regulator. The generator must be restarted and terminal voltage must be checked once it has been generated. If the terminal voltage doesn't come on, try field flashing again, or check out the troubleshooting guide.

Installing a Replaceable Bearing

Using a bearing puller, remove the existing bearing. Once the bearing has been removed from the shaft, it should be replaced. It is imperative that when replacing bearings, you use the EXACT SAME TYPE and SIZE as the ones that came with the machine.

When placing an order from the parts list, be sure to include both the unit's serial number and the corresponding part number. It is recommended to heat the bearing to no more than 100 degrees Celsius (212 degrees Fahrenheit) in an oven.

A light layer of clean lubricating oil should be applied to the rotor shaft's press fit area. With heat-resistant gloves on, slide the bearing over the shaft's end until it meets the shoulder of the shaft. The bearing must be pressed onto the shaft and seat, but not too firmly.

If the bearing gets caught on the shaft prior to being put against the shoulder, you can use a piece of tubing that is slightly larger than the press-fit region to push the bearing into its ultimate position. Apply light pressure with a delicate mallet, focusing just on the inside race.

Rectifier Assembly Removed

The rectifier assembly must be taken apart before the opposite drive end bearing bracket and bearing can be taken apart. Take off the three exciter rotor leads from the heat sinks and the two main rotor leads from the main rotor posts. Remove the screws holding the rectifier assembly to the shaft to remove it.

Diode Replacement

Before reinstalling the diode on the heat sink, a thin layer of conductive heat sink compound should be applied around its base (do not coat the threads). When mounting a diode to a heat sink, you should be cautious not to overtighten the retaining nut.

Up to 28 lb-ft of torque existing lead wire from failed diode may be unsoldered and resoldered on replacement if not damaged.

Final thoughts

When it comes to generators, nobody does it better than Marathon, who have a solid reputation for producing robust models that can withstand the harshest environments. I would suggest checking out their offerings especially if you're in a remote and difficult environment.

About Tom Bell

Hey, I’m Tom, the owner of Generator Reviews! I built this website to help you get the very most out of your generator and select the correct one for your personal circumstances. This site contains reviews of virtually every generator, detailed buying guides, as well as maintenance advice to help you keep yours in tip-top shape!

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