Generator set

A generator set is often the central energy source on construction sites, in concrete demolition, in special demolition, as well as in rock excavation and tunnel construction. It reliably supplies electrical consumers with voltage and frequency-from the hydraulic power pack for concrete demolition shear or hydraulic wedge splitter to lighting, ventilation, pumps, and measuring instruments. Especially where no power connection is available or the supply is unreliable, a suitable generator set enables the planned deployment of the tools and systems from Darda GmbH. In temporary or remote operations, a correctly specified generator set increases schedule reliability and protects connected equipment through stable power quality.

Definition: What is meant by a generator set?

A generator set (also generator, power generator, or backup power unit) is understood to be a unit consisting of a prime mover and a generator that converts mechanical into electrical energy. Jobsite-ready units usually deliver 50 Hz at 230 V (single-phase) or 400 V (three-phase) and are designed to ensure the starting currents of motors, voltage stability, and protective functions for the safe operation of electrical consumers. For applications by Darda GmbH-such as supplying hydraulic power packs, which in turn drive concrete demolition shear, combi shears, Multi Cutters, steel shear, cutting torch, or rock wedge splitter-a generator set is frequently the link between construction site reality and reliable power supply. In practice, auxiliary features like automatic start, remote monitoring, and fuel safety provisions can further increase operational reliability. Always verify regional voltage and frequency requirements before commissioning.

Design and operating principle of a generator set

A typical jobsite generator set consists of an internal combustion engine (diesel or gasoline), a synchronous generator, control (AVR or inverter), fuel system, acoustic enclosure, cooling, and protective devices (overcurrent, temperature, oil, RCD/residual current protection if present). The generator produces single- or three-phase power depending on the configuration. An automatic voltage regulator (AVR) keeps the voltage stable during load changes; inverter generator sets shape the generator voltage into an especially clean AC waveform with low total harmonic distortion (THD). For operating the electric motors in hydraulic power units, voltage and frequency stability is crucial to positively influence starting behavior, heating, and service life.

Brushless alternators with AVR are common on jobsites; versions with separate excitation or permanent magnet generators (PMG) offer improved short-term stability during motor starts. Pay attention to enclosure sound attenuation, insulation class, and ingress protection of outlets and distribution gear. Where controls and sensors are sensitive, inverter variants can provide additional headroom on power quality.

Requirements in concrete demolition, special demolition, and rock excavation

In Darda GmbH’s application areas, a generator set encounters specific requirements:

• Concrete demolition and special demolition: selective deconstruction with concrete demolition shear, combi shears, and Multi Cutters requires a quiet, low-emission, and voltage-stable supply-often in city centers or buildings with sensitive surroundings.
• Building gutting and cutting: varying loads, frequent starts of the hydraulic power packs, additional consumers such as slurry and cooling water pumps as well as lighting.
• Rock excavation and tunnel construction: island operation, long cable runs, dust exposure, limited ventilation; generator sets are preferably positioned outside critical areas.
• Natural stone extraction: continuous operation for hydraulic wedge splitter and rock wedge splitter, robust construction, long runtimes, and fuel autonomy; including rock and concrete splitters.
• Special deployment: temporary grid feed-in, redundancy, special protective measures, and load management for sensitive devices.
• Environmental and compliance aspects: site-specific restrictions on noise and exhaust, handling of fuel near water protection zones, and documentation obligations for inspections.

Sizing: correctly planning kW, kVA, and starting currents

Correct sizing begins with the sum of all power ratings, the type of consumers, and their switching behavior. Hydraulic power packs for concrete demolition shear and hydraulic wedge splitter are often driven by three-phase motors whose starting current can be multiple times the rated current. Reserve capacity is essential to avoid voltage dips and nuisance trips of protective devices.

Basics of power rating

Generators are specified in kVA. For resistive loads, kW ≈ kVA × cos φ. With motor loads, power factor and efficiency must be considered. In addition, reserves must be provided for starting currents. As a rule of thumb, plan apparent power for the continuous load plus a headroom tailored to the highest starting current and the regulation dynamics of the generator set.

Starting currents of motors

• Direct-on-line start: typical starting current 5–7 × rated current
• Soft starter/frequency converter: starting current 1.5–3 × rated current
• Star-delta start: typically 2–3 × rated current when correctly applied and permitted by motor design
• Hydraulic power packs with pressure relief at startup noticeably reduce the starting demand

Example calculation (simplified guidance)

A 7.5 kW three-phase motor (cos φ ≈ 0.85) for a hydraulic power pack supplying a concrete demolition shear:

• Rated apparent power: 7.5 kW / 0.85 ≈ 8.8 kVA
• With direct-on-line (6 ×): generator set often 3–4 × rated apparent power → approx. 26–35 kVA
• With soft starter (2 ×): generator set 1.6–2.5 × → approx. 14–22 kVA

Note: These are practice-oriented reference values. Exact figures depend on motor data, starting method, generator regulation (AVR/inverter), and cable lengths. Include additional consumers and plan an appropriate safety margin for environmental influences and aging.

Load management and power peaks

Consumers operated in parallel (e.g., hydraulic power pack, pump, lighting) should be switched so that starting peaks occur at different times. Never start all large motors simultaneously unless the generator set is sized for it. Sequenced starting via soft starters, time relays, or drive ramps significantly stabilizes the voltage and frequency profile.

Power quality, frequency, and protective functions

For the reliable supply of hydraulic power packs and controls, THD, voltage regulation, and frequency constancy are important. Inverter generator sets deliver a very clean sine wave; classic synchronous generators with AVR are robust and well suited for motor loads when adequately sized.

Voltage drop and cable lengths

Long feeders between the generator set, site distribution board, and consumers increase voltage drop and the required starting current. Larger cable cross-sections and short cable runs improve the starting behavior of the motors in hydraulic power packs. As guidance, aim for ≤ 3% voltage drop on individual feeders and ≤ 5% in total under operating load.

Protective measures

• Residual current protection: selection and use must always comply with general electrical rules; special versions may be required with variable-speed drives.
• Earthing/equipotential bonding: plan depending on location and application; island operation, ground rods, and bonding to conductive parts must be professionally assessed.
• Overcurrent/overtemperature protection: ensure adequate protection of the outgoing circuits and observe the protective devices specified by the manufacturer.
• Insulation and phase sequence monitoring: in isolated operation, use appropriate monitoring; verify correct rotation for three-phase motors before loading.

Fuel, emissions, and noise

The choice of prime mover affects operation, environment, and permitting.

• Diesel generator sets: high efficiency and long runtime, suitable for continuous operation.
• Gasoline generator sets: light and compact, often for smaller outputs and mobile deployments.
• Sound-insulated enclosure: reduces sound power level-important for inner-city deconstruction with concrete demolition shear or combi shears.
• Exhaust routing and ventilation: exhaust gases must not flow into work areas or tunnel zones; plan sufficient fresh air supply.
• Emission requirements: vary by region; deployments in sensitive areas may require additional measures.
• Fuel logistics: provide safe storage, spill containment, and refueling concepts matched to runtime and access constraints.

Installation, transport, and environmental influences

For a generator set to reliably feed Darda GmbH’s hydraulic power packs, location and peripherals must be carefully planned.

Installation site

• Firm, level ground, sufficient distance from buildings and combustible materials
• Good ventilation, no recirculation of hot exhaust air
• Weather protection, IP-rated sockets/distribution boards for dust and moisture
• Vibration control and anchoring as required to protect devices and cabling

Cables and distribution

• Adequate conductor cross-section to limit voltage drop
• Robust site distribution boards, mechanical protection against damage
• Labeling of circuits and clear assignment of loads
• Verification of phase sequence and correct motor rotation before commissioning

Derating and operating altitude

At high ambient temperature or great elevation above sea level, available power and cooling reserve decrease. Provide design margins. Typical guidance: consider approx. 1% power reduction per 5 K above 25 °C and approx. 3% per 300 m above 1000 m, unless manufacturer data specify otherwise.

Practical application scenarios with Darda GmbH products

• Concrete demolition in a city center: a soundproofed diesel generator set supplies an electrically driven hydraulic power pack that drives a concrete demolition shear. Starting currents are limited via a soft starter; lighting and dust extraction run on separate feeders.
• Natural stone extraction in a quarry: a robust three-phase generator set feeds hydraulic power packs for hydraulic wedge splitter and rock wedge splitter. Long feeders are installed with larger cross-sections to reduce voltage drop.
• Tunnel advance and special deployment: the generator set is positioned outside the tunnel tube; hydraulic power packs for combi shears, Multi Cutters, or steel shear are supplied via weatherproof distribution boards, keeping waste heat and exhaust gases outside the workspace.
• Strip-out and cutting in existing buildings: a compact generator set provides 400 V for the hydraulic power pack and 230 V for auxiliary consumers; starting peaks are managed by staggered switching.
• Night-time selective deconstruction near sensitive areas: a low-noise generator set operates behind temporary acoustic barriers; refueling and maintenance are scheduled to avoid operational peaks.

Operation, maintenance, and availability

The availability of a generator set determines the workflow on the construction site-especially when hydraulic power packs for concrete demolition shear or hydraulic wedge splitter run continuously.

• Observe maintenance intervals (oil, filters, cooling, seals)
• Ensure fuel quality; refuel only when stopped and with spill protection
• Test protective devices; visual inspection of cables and plug connections
• Keep spare parts and operating supplies in stock; document operating hours
• Conduct periodic load tests under realistic conditions and monitor voltage, frequency, and THD
• Maintain starter batteries and keep replacement belts, fuses, and RCDs appropriate to the installation concept

Costs, efficiency, and load profile

Cost-effectiveness depends heavily on the load profile. An oversized generator set operated continuously in partial load consumes relatively more fuel. Better is a sizing that efficiently covers the typical continuous load and absorbs power peaks via start management, soft starter, or short-term higher reserves. Where possible, load bundling and temporal staggering can reduce fuel consumption and lower noise emissions. Avoid prolonged low-load operation on diesel engines to prevent unfavorable operating states; plan for periodic higher-load phases when feasible.

Checklist for selection and operation

1. Record consumers: power, phase (230/400 V), starting behavior; prioritize hydraulic power packs for concrete demolition shear and hydraulic wedge splitter.
2. Determine generator set rating: kVA with reserves for starting currents, voltage stability, and cable lengths.
3. Quality of supply: select AVR or inverter to suit motor loads and controls.
4. Fuel and noise: check runtime needs, and emission and noise requirements at the deployment site.
5. Installation and cables: plan ventilation, weather protection, cross-sections, protective devices, earthing/equipotential bonding.
6. Load management: define start sequence, avoid concurrent peaks.
7. Maintenance and documentation: organize intervals, operating hours, inspections, and spare parts stocking.
8. Commissioning: verify voltage, frequency, and phase sequence under load; confirm correct tripping of protective devices.
9. Environmental margins: account for temperature and altitude derating and set appropriate alarm thresholds in controls.

Technical deep dive: interfaces to hydraulic power packs

Darda GmbH’s hydraulic power packs convert electrical into hydraulic power for tools such as concrete demolition shear, combi shears, or a rock wedge splitter. For trouble-free operation, the following is recommended:

• Adequate generator inertia and regulation quality so that pressure spikes (load steps) at the hydraulic valve do not cause the voltage to collapse.
• Use soft starters or frequency converters as appropriate; ensure compatible residual current protection technology.
• Start hydraulics preferably with a depressurized system; design control so the motor is only loaded after reaching nominal frequency.
• Keep voltage drop on the feeder to the hydraulic power pack low; select plugs and couplers with a degree of protection appropriate to the environment.
• Check phase sequence and motor rotation before coupling to the hydraulic load; use phase-failure and undervoltage relays where suitable.
• With drives that can feed energy back, avoid regenerative operating states toward the generator; use braking resistors or adapted ramp-down profiles if needed.