Fixed speed, simple sequence
Review DOL or star-delta starting against supply limits and machine acceleration.
SOLUTIONS / APPLICATION GUIDE
Motor controls & automation
Compare starting methods around the machine, supply and operating sequence. Plan control, protection and commissioning together.
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CHOOSE YOUR APPROACH
Start with the application.
Controlled acceleration
A soft starter may suit a fixed-speed duty; starting torque and thermal limits still matter.
Variable process demand
A VFD can control speed. Review motor compatibility, harmonics, cooling and cable length.
BUILD A USEFUL BRIEF
Bring these details.
- Motor nameplate, voltage and full-load current
- Driven machine, torque profile and starts per hour
- Control voltage, interlocks and emergency-stop requirements
- Cable length, environment and supply capacity
Can any motor use star-delta starting?
No. It needs a suitable three-phase motor, accessible winding terminals and a voltage rating compatible with delta operation on the supply. Verify the nameplate and load torque.
COMPONENTS THAT COMPLETE THE APPLICATION
Specify the whole working system.
Start with the equipment duty. Add the control, protection and measurement functions that your project needs; these are options to review, not a pre-approved assembly.
Images are AI-generated illustrations of equipment categories, not LOVATO model photographs. Confirm dimensions and ratings from the selected model datasheet.
Motor protection & control
Motor protection circuit breakers
Protect individual motor circuits as part of a coordinated starter.
Confirm: Motor full-load current · fault level · starter coordination.
Compare selection details ↗
Motor protection & control
Contactors
Switch motors or other loads using the appropriate utilisation category.
Confirm: Load type and duty · coil supply · auxiliary contacts.
Compare selection details ↗
Motor protection & control
Motor protection relays
Monitor overload conditions within the motor protection scheme.
Confirm: Motor current · trip class · reset strategy.
Compare selection details ↗Motor protection & control
Soft starters
Explore controlled starting for fixed-speed machinery.
Confirm: Starting torque · load inertia · bypass arrangement.
Compare selection details ↗
Motor protection & control
Variable speed drives
Match motor speed to process demand where the application permits.
Confirm: Motor current · load torque · speed range and cooling.
Compare selection details ↗Control & signalling
Pushbuttons and selector switches
Define clear local commands and machine operating modes.
Confirm: Operator function · contact blocks · ingress protection.
Compare selection details ↗
Automation & control
Micro PLCs and HMI
Define the operating sequence, inputs and operator interface together.
Confirm: I/O schedule · communications · operator screens.
Compare selection details ↗Automation & control
Switching power supplies
Budget the control-system DC demand and start-up requirements.
Confirm: Output voltage · continuous current · inrush and derating.
Compare selection details ↗Explore all 36 component families ↗
Continue into equipment & assemblies
Motor Control & Automation ↗DOL & Star-Delta Starter Panels ↗Variable Frequency Drive (VFD) Panels ↗PLC, SCADA & BMS Automation Panels ↗METHODS & WORKED EXAMPLES
Understand the estimate.
These examples use the default inputs. Change the live controls above for your own scenario; the reference examples below remain fixed.
Motor starting current — worked example
Example inputs
- Motor rating: 55 kW
- System voltage: 415 V — industrial
- Phase: 3Φ (three phase)
- Starting method: Direct on line (DOL)
- Efficiency: 92 %
- Power factor: 0.86
Example result
- Full load current: 96.7 A
- Starting current: 580 A
- Starting multiplier assumption: 6 × FLC
Assumptions & limits
- Starting multipliers are illustrative, not measured inrush or guaranteed torque.
- Verify motor nameplate, load acceleration, supply limits and starts per hour.
- Preliminary planning only. Final selection needs project-specific engineering verification.
Motor energy comparison — worked example
Annual kWh = rated shaft kW × load fraction × annual hours / efficiency fraction. Cost difference uses the entered energy tariff.
Example inputs
- Rated shaft power: 30 kW
- Shaft load: 75 %
- Existing efficiency at duty: 88 %
- Replacement efficiency at duty: 93 %
- Annual running hours: 4000 h
- Energy tariff assumption: 25 KES/kWh
- Installed replacement cost: 150000 KES
Example result
- Existing annual energy: 102,272.7 kWh
- Replacement annual energy: 96,774.2 kWh
- Annual cost difference: 137,463 KES
Assumptions & limits
- Both motors deliver the same shaft duty. Use efficiency at this load, not an unrelated nameplate point.
- Tariff is your scenario input, not a published utility rate.
- Simple payback excludes finance, maintenance, downtime and tariff changes. Negative difference means higher operating cost.
- Preliminary planning only. Final selection needs project-specific engineering verification.
Technical reference: US Department of Energy: motor systems guide. This reference does not certify the website calculation or an NPE assembly.
MCB / MCCB / ACB sizing — worked example
Example inputs
- Load value: 160
- Unit: Amps
- System phase: 3Φ (three phase)
- System voltage: 415 V — industrial
- Load profile: General power
- Fault level: 25 kA
- Altitude: 1700 m
- Ambient temperature: 35 °C
Example result
- Nominal rating (In): 200 A
- Device frame: MCCB (moulded case)
- Tripping curve: Curve C (5–10× In)
Assumptions & limits
- Altitude derate: 0 % at 1700 m
- Temperature derate: 4 % at 35 °C
- Load profile factor applied: 1.1×
- Preliminary planning only. Final selection needs project-specific engineering verification.
METHODS & WORKED EXAMPLES
Understand the estimate.
These examples use the default inputs. Change the live controls above for your own scenario; the reference examples below remain fixed.
DC control power budget — worked example
Example inputs
- DC output voltage: 24 V DC
- PLC and other continuous load: 25 W
- Simultaneously held DC coils: 6
- Holding power per DC coil: 3 W
- Simultaneous sensors: 10
- Power per sensor: 0.5 W
- Reserve allowance: 25 %
Example result
- Connected continuous load: 48 W
- Budget with reserve: 60 W
- DC output current budget: 2.5 A
Assumptions & limits
- Pload = PLC / other W + coil count × holding W + sensor count × sensor W.
- Pbudget = Pload × (1 + reserve / 100); Ibudget = Pbudget / DC voltage.
- Reserve is a planning assumption, not a manufacturer requirement.
- All listed loads must match the selected DC voltage. AC coil VA and DC coil watts are not interchangeable.
- Check coil pull-in peaks, simultaneous starting, temperature and altitude derating, overload behaviour and branch protection separately. This tool does not select a supply model.
- Preliminary planning only. Final selection needs project-specific engineering verification.
Method reference: MEAN WELL — Power supply selection FAQ
Three-phase voltage unbalance — worked example
Example inputs
- L1–L2 voltage: 415 V
- L2–L3 voltage: 410 V
- L3–L1 voltage: 420 V
Example result
- Average line voltage: 415 V
- Maximum deviation: 5 V
- Voltage unbalance: 1.2 %
Assumptions & limits
- Unbalance (%) = 100 × maximum absolute deviation from the average / average.
- Use line-to-line readings taken under the same operating condition.
- No pass/fail limit or trip delay is selected. Check equipment limits and investigate supply conditions with a qualified engineer.
- This method uses voltage magnitudes only; it is not an IEC negative-sequence calculation.
- Preliminary planning only. Final selection needs project-specific engineering verification.
Method reference: US DOE — Energy Management for Motor-Driven Systems