Mobile diesel generator mounted on a trailer, used to supply large sets with electrical power when no permanent tie-in is available.
Technical Details
Standard tow plants use air-cooled Deutz or Perkins diesel engines running at 1500 rpm, generating a constant 50Hz mains frequency via synchronous generators. Typical models like the Himoinsa HYW-45 deliver 45 kVA with a 68-liter fuel tank, achieving 12 hours of runtime at 75% load. Soundproofed variants (Super Silent) reduce noise levels to below 65 dB at 7 meters. Automatic Voltage Regulators (AVR) ensure a constant 230V ±2%, while digital controllers monitor operating hours, fuel consumption, and maintenance intervals.
History & Development
Tow plants became established from the 1960s onwards, paralleling the development of portable HMI lights in Hollywood. Early models from Onan and Kohler reached 15-25 kVA and weighed over 800kg. With the introduction of low-noise units by Himoinsa (1986) and later GenSet, these became practical for sound recording in film productions. Modern LED lighting has significantly reduced power demands, making compact 20-45 kVA generators sufficient where 100+ kVA were previously required.
Practical Use in Film
On "Mad Max: Fury Road" (2015), 12 tow plants of 100 kVA each powered the desert shoots in Namibia, as mains power was unavailable. Night shoots for "Blade Runner 2049" utilized low-noise 45 kVA units for HMI daylight fixtures without sound interference. In the series "The Crown," mobile generators enabled filming in historic buildings without access to the power grid. Standard practice: place generators at least 20m away from sound recording, distributing power via rubber cable ramps and CEE distribution boxes.
Comparison & Alternatives
Tow plants differ from stationary units by having an integrated drawbar and road homologation. Container generators (from 200 kVA) require crane transport but offer higher output for large productions. Modern lithium battery packs, such as the Voltstack series, replace small generators for short shoots but have a maximum capacity of 20 kWh. Hydrogen fuel cells (Toyota Mirai technology) are used for emission-free interior shoots but cost three times as much as conventional diesel units.