Nominal voltage is a fundamental rating of electrical equipment and determines under which supply conditions machines, drives, and controls operate safely and with the intended performance. In the context of Darda GmbH’s hydraulic demolition and splitting technology—from hydraulic power units for demolition through hydraulic rock and concrete splitters to concrete demolition shears—the selected nominal voltage directly affects deployability, cycle times, and operational safety on the construction site. Anyone planning demolition works, building gutting, rock excavation, or natural stone extraction should consider nominal voltage early to design power supply networks, cable routing, and generator sets appropriately.
Definition: What is meant by nominal voltage
Nominal voltage is the voltage specified by the manufacturer for which an electrical device, assembly, or system is designed. It describes the range in which the intended functions are reliably fulfilled under normal environmental conditions. Nominal voltage must be distinguished from the actual operating voltage, which can fluctuate depending on network quality, load condition, and cable length. For AC, ratings such as 230 V or 400 V indicate the voltage level, often supplemented by the nominal frequency (e.g., 50 Hz). In hydraulic power packs that drive concrete demolition shears or rock and concrete splitters, nominal voltage in particular defines the design of electric motors, controls, and protective devices.
Nominal voltage in hydraulic power packs and drive technology
Darda GmbH hydraulic power packs are available in various electrical versions, typically as 230 V single-phase or 400 V three-phase variants. The chosen nominal voltage influences inrush current, available pump speeds, and thus pressure and flow rate. Undervoltage leads to longer cycle times, increased heating, and possible tripping by motor protection. Overvoltage can overload components. For continuous work such as concrete demolition, special demolition, or tunnel construction, 400 V is often used because three-phase networks provide more stable starting and continuous power. Indoors or for temporary deployments, 230 V can be sensible, provided cable routing and protection are coordinated accordingly.
Significance of nominal voltage for rock and concrete splitters and concrete demolition shears
For rock and concrete splitters and concrete demolition shears, the nominal voltage of the hydraulic power pack’s supply indirectly affects mechanical performance: A stably supplied motor delivers the calculated flow to the pump—the hydraulic pressure builds quickly, and the splitter cylinder or the shear achieves its designed force predictably. Voltage drops caused by extension leads that are too long or too thin, by contrast, lead to slower stroke movements, delayed pressure build-up, and higher stress on the power packs. For precise building gutting, controlled rock excavation, or natural stone extraction, a power supply matched to the nominal voltage and correctly dimensioned cables are therefore crucial.
Typical voltage levels on construction sites
In German-speaking countries, 230 V (single-phase, 50 Hz) and 400 V (three-phase, 50 Hz) dominate. Three-phase networks offer advantages in hydraulic applications regarding starting torque and efficiency. For temporary construction power supply systems, ensure correct protection, suitable plug devices, and sufficient network stability.
Voltage drop, cable lengths, and conductor cross-sections
Voltage drop along extension leads is one of the most common causes of performance issues. The longer the cable and the smaller the cross-section, the more the voltage at the power pack drops—especially critical during motor start. This leads to increased current draw, heating, and possibly activation of protective devices. Cable routing matched to the nominal voltage with an appropriate cross-section keeps voltage drop within permissible limits.
Practical rules to minimize voltage drop
- Route cables as short as possible; avoid unnecessary lengths.
- Select a sufficient conductor cross-section; prefer larger cross-sections.
- Fully unwind cable reels to reduce thermal loading.
- Measure or observe devices under load (start-up behavior, motor protection tripping).
- Use three-phase supply (400 V) for high loads where permitted and available.
- Place supply points as close to the hydraulic power pack as possible.
Frequency and network type: impact on motors and pumps
Besides nominal voltage, network frequency (typically 50 Hz) is decisive. Deviations change the speed of induction motors and thus the pump flow rate. Operate equipment only within the ranges indicated on the nameplate. Network types (e.g., TN or TT systems) and their protective measures influence the choice of residual current protection and grounding. These points must be clarified carefully in advance of the work—especially in tunnels, access shafts, and temporary construction power supply distributions.
Nominal voltage with mobile generator sets
Those operating hydraulic power packs via mobile generator sets must ensure that the nominal voltage remains stable—even during load transients such as motor start. Suitable voltage regulation (e.g., AVR) and sufficient power reserves are important. Unfavorable combinations of small generator capacity, long cables, and high inrush currents lead to undervoltage, which immediately manifests as longer cycle times of concrete demolition shears or reduced splitting performance. Grounding and protective measures must be executed in accordance with generally accepted engineering practice.
Protective measures, IP ratings, and environmental conditions
The electrical equipment must match the nominal voltage and the environment. IP ratings indicate suitability for dust, moisture, and splashing water—a relevant aspect in deconstruction, in tunnel heading, or in the quarry. Residual current protection devices and correct overcurrent protection complement safety. In potentially conductive environments (wet surfaces, contact with reinforcing steel), pay particular attention to the proper condition of cables, plugs, and couplers.
Low-voltage controls and auxiliary voltages
In addition to the mains nominal voltage for drives, many systems use auxiliary voltages (e.g., 24 V DC) for controls, solenoid valves, or remote controls. Stable supply of these circuits is important so that safety and control functions remain reliable. Voltage drops in auxiliary circuits show up as delayed switching or faults that can be misinterpreted as hydraulic problems.
Planning and use in concrete demolition, building gutting, and rock excavation
In deployment planning for concrete demolition and special demolition, building gutting, rock excavation, and tunnel construction, nominal voltage should be treated as its own work step: Where is the feed (230 V or 400 V), how are the cables routed, what cross-sections are required, and what load profiles will occur? For rock and concrete splitters, this can determine the achievable splitting force per time window; for concrete demolition shears, it affects uniform closing and opening times, which are essential for controlled demolition works.
Marking, nameplates, and documentation
Nominal voltage is indicated on the hydraulic power pack’s nameplate and in the technical documentation, often supplemented by rated current, frequency, and IP rating. Symbols such as “~” (AC) or “3~” (three-phase) facilitate assignment. These details are the binding basis for selecting connectors, overcurrent protection, and cable cross-section.
Practical examples from application areas
- Concrete demolition indoors: A 230 V power pack supplies a concrete demolition shear. Short, adequately sized cables prevent voltage drops and keep cycle times stable.
- Tunnel construction: 400 V three-phase supply with central construction power supply distribution. With coordinated cross-sections and short feeders, hydraulic pumps operate in the optimal range.
- Natural stone extraction in the quarry: Operation via a generator set. Power reserve and voltage regulation ensure that rock splitters complete their splitting cycles without undervoltage.
Accessories and compatibility
When combining power pack, cables, and controls, ensure that the nominal voltages of all components match. Different plug systems and codings serve to avoid incorrect connections. Solenoid valves, remote controls, and sensors must be supplied according to their auxiliary voltages so that the hydraulic function of concrete demolition shears and splitter cylinders can always be actuated safely.
Use terms correctly
Nominal voltage denotes the design value. Operating voltage is the actual voltage present in operation and may differ. Test voltage describes voltages used to stress components for testing; it is not relevant in normal operation. For the design of hydraulic power packs, their motors, and protective devices, nominal voltage is always decisive.
Checklist: Consider nominal voltage in the workflow
- Check nominal voltage and frequency on nameplates (power pack, controls, accessories).
- Define the supply level (230 V or 400 V) and provide suitable connectors.
- Plan cable routing: as short as possible; dimension cross-sections adequately.
- Assess voltage drop; fully unwind cable reels.
- For generator set operation, ensure power reserve and voltage regulation.
- Adapt protective measures (overcurrent protection, residual current protection, IP rating) to the environment.
- Perform a functional test under real load; observe start-up behavior and cycle times.