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Alternators and inverters are changing to better provide electrical power for motorcoaches

Alternators and inverters are key to operating motorcoaches today. With all of the electronic devices on a coach, from lights to video to air conditioning, more electrical power is needed.

And batteries can only provide so much energy. Enter alternators and inverters.

“From an operator’s point of view, they obviously want reliability, they want up time and they want to obviously have the system deliver to their requirements,” says Clive Harley, corporate VP of engineering for Prestolite Electric, a manufacturer and supplier of alternators, starters and other electrical equipment and services.

While the basics of alternators and inverters haven’t changed much over the years, there have been improvements in form and function that benefit motorcoach operation.

Harley says that alternators have become smaller and have more power density, which makes them more efficient. Key to this is the lowering of internal resistance and temperature, done by use of higher-grade materials in the magnetic circuit.

“They typically have a lot more output now than they have had over the last 20 years,” he said. “Now you have 350 to 400 amps. Obviously [operators] want to run TVs and lights, so the alternators need to work nicely with the inverters. They also need to be able to recharge the batteries.”

Harley also said that different winding technologies for the stator, the stationary electrical generating part, are being used—much thicker conductors arranged in a different structure makes use of all of the space available, as well as get rid of unnecessary heat.


Design changes

Harley pointed out that it’s important to have the motorcoach manufacturer involved when adding electronic accessories so they can be built into the design of the vehicle.

“The fundamental design of the vehicle doesn’t include additional loads, like third-party inverters,” he said. “Some inverters are not well protected in the sense of electrical noise.”

According to Harley, some third-party inverters don’t have good electrical noise dampeners, and they have components that produce voltage spikes in the system. Those spikes can damage things like engine control units and alternator regulators, possibly rendering any warranties void.

“Component selection is important,” he said. “Stick with the manufacturer’s recommendations. If you want to put an inverter on, go back to the manufacturer. It’s the best course of action.”


Future power

While the basics of alternators and inverters haven’t really changed, Harley does see some improvements coming.

“We’ve got product with inverters built into the alternator and that’s used in motor-generator capabilities,” he said. “So, in some cases, you’ve got an alternator-looking device that has an inverter built onto the back of it. What that system allows for is good action between the alternator and the inverter.”

Harley said this design allows for the alternator to become a motor in some cases.

“For example, you could have the power steering pump driven off the motor side of the alternator,” he said. “So, you have two belts. With one belt, the engine drives the alternator and if you want the alternator to drive the power steering pump, the clutch opens up, the engine disengages, and the alternator becomes a motor and drives the power steering pump, or the motor for the air conditioning unit.”

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