By Mike Sokol • July 30, 2018 An "old school" WhisperWatt 125 AC generator. Back in the day all generators for stage productions were large, diesel-powered beasts. Pulled in on a trailer, the good ones were quiet, had a large enough fuel tank to last through a show (and then some), and offered single-phase 120/240-volt or 3-phase 120/208-volt power. We hooked them up with Cam-Lok connectors using 2/0 or 4/0 cable and often placed them up to 100 feet from the stage on pavement so they didn’t sink in the mud. A large show, also with lots of tungsten (ugh) lighting, usually required one or more WhisperWatt 25 to 125 kVA (kilo-volt-ampere) generator(s). But the times they are a changin’, and with the introduction of more efficient power amplifiers, smaller instrument amplifiers (or none at all), and LED lighting, the need for 100 kW of electrical power to run a show has largely been eliminated (unless you’re doing something on a Beyoncé or Trans-Siberian Orchestra scale, of course). I’ve worked a bunch of medium-sized outdoor events in the last few years where we didn’t have to rent a traditional trailer-mounted “genny” and run all of the accompanying heavy 2/0 feeder, but rather simply deployed one of the newer gasoline inverter generators and downsized power distribution. Remember that today, unless it’s a reggae or hip-hop show, actual power requirements for a modern PA system are about 1/8 of rated power. So a 12 kW (kilowatt) system will only need about 1,500 watts of actual power. Of course, mileage can vary depending on things like amplifier and lighting power factors, but it’s pretty amazing how much power can be delivered by modern inverter generators. Likely Suspects Inverter generators work differently than classic AC (alternating current) units since they don’t produce AC voltage directly. In an AC generator, there’s a gas or diesel engine locked to a specific RPM (revolutions per minute) by a governor that spins what’s essentially a big magnet to produce the power directly. So as the engine speed goes up or down from load changes, so does the frequency of the power. Likewise, don’t assume that power is actually at the desired 60 Hz unless it’s measured/verified with a meter. While running at 59 or 61 Hz generally isn’t a problem with most modern electronics, it can wreak havoc with a Hammond B3 organ that has its tone wheels locked to the line frequency with a synchronous motor. In an inverter generator, power actually starts out as 12-volt DC (direct current). which is then stepped up to 120-volt AC via a sine-wave inverter. The beauty of this is that the frequency and voltage output of the generator are under electronic control, and the AC power from an inverter generator is often cleaner than what comes off the utility pole. In addition, they can be set to an “eco-throttle” mode when a lot of power isn’t required, which allows the engine to automatically reduce its RPM (and noise) down to more of an idle speed. I use this mode for jazz, bluegrass, public speaking and outside wedding events where background noise must be kept to a minimum. The miniscule Honda EU2200i (left) and muscular EU7000iS inverted generators. Honda is a leader of the pack when it comes to smaller, quieter, inverter units. While other sources offer great options as well, most of the rental houses I work with only supply Honda models, which deliver extended engine life, clean power, and low noise levels. Here are three units in my own inventory and/or that I rent for small- and medium-size outside shows. First up is the Honda EU2200i, rated at 2,200 watts with a duplex 120-volt/20 amp and twist-lock outlet (on the companion version). I employ it for smaller political events (ground-breaking ceremonies, roadside stages, acoustic acts, etc.). The original Eu2000i is nearly as capable, albeit without the twist-lock 30-amp AC outlet for parallel mode, which allows you to hook a pair of them together for twice the wattage output. Both weigh about 50 pounds, will run most of the day on a gallon of gas, and are so quiet that you can often stash them right behind the stage without running long power cables. Next is the Honda EU3000iS, offering electric start and rated at 3,000 watts, although only 120 volts is available on a 3-wire/30-amp twist-lock outlet. It’s super quiet and has a 3.6-gallon fuel tank that only needs a single filling to run all day. Weight is at about 130 pounds, with a downside being no built-in wheels or handles. I’ve used this model for events with up to 36 LED lighting instruments, and a 6,000- to 12,000-watt PA system. Finally, there’s the Honda EU7000iS, rated 7,000 watts with 120/240-volt available on a 4-wire/30-amp twist-lock outlet. It will easily support long events on just 5 gallons of fuel. Weight is 260 pounds, but there are integrated wheels and flip-up handles so it’s easy to move around. I’ve run some significantly large sound and lighting systems off of just one of these, and they usually rent for around $100 per day. Read the rest of this post 1 2 About Mike Mike Sokol System Designer & Audio Educator Mike Sokol does sound system design and training for JMS Productions, his consulting company in Western Maryland. Visit www.livesoundadvice.com for his educational articles and videos, and email him at [email protected] with comments and suggestions. http://www.livesoundadvice.com Tagged with: AC Concerts electricity Festivals generators Grounding Live Sound International Mike Sokol Power Sound Reinforcement Systems · all topics Subscribe to Live Sound International Subscribe to Live Sound International magazine. Stay up-to-date, get the latest pro audio news, products and resources each month with Live Sound.