Electrical calculation

Transformer & MCC
sizing

Estimate coincident demand, transformer rating, MCC incomer and busbar capacity from project-defined load groups and design criteria.

Registration required for results

Project criteria remain blank.Enter approved demand, loading, derating and impedance values. The rating ladders are preliminary only and do not constitute selection of a transformer, breaker or MCC assembly.

01 / Project inputs

Define the electrical demand

Your details

Required so Metsiworx can retain the calculation record and contact you if an engineering concern is identified.

Full nameOrganisationEmail addressTelephone

Project

Project or pump stationClient or municipalityProject locationSupply or MCC reference

Load groups

Enter electrical input kW, not motor shaft-output kW. Demand factors represent the expected coincident operating proportion.

Load group 1 · requiredDescription

QuantityInput per unitkWDemand factor%Power factor

Load group 2 · optionalDescription

QuantityInput per unitkWDemand factor%Power factor

Load group 3 · optionalDescription

QuantityInput per unitkWDemand factor%Power factor

Load group 4 · optionalDescription

QuantityInput per unitkWDemand factor%Power factor

System and design criteria Required project criteria

LV line voltageVDesign margin%Maximum transformer loading%Transformer derating factor%Transformer impedance%Maximum busbar loading%

Transformer fault current is calculated at its LV terminals from entered percentage impedance, assuming a stiff upstream source. Actual upstream impedance, LV cable impedance and rotating-machine contribution are excluded.

Calculation and equipment reference basisTransformer: applicable SANS 780, IEC 60076 and utility/project requirements. LV MCC assembly: applicable SANS/IEC 61439-1 and 61439-2. Incomer: current ABB SACE technical data, with ABB preferred by Metsiworx.The calculator determines required ratings only. Confirm the transformer manufacturer's offered standard size and impedance; confirm the selected ABB breaker frame, trip unit, rated voltage, breaking capacity and discrimination; and obtain design verification for the complete MCC assembly.

02 / Registration requiredSubmit your details to view the calculation.

The full calculation record will be delivered to Metsiworx.

02 / Preliminary result

Awaiting inputs

Preliminary common transformer rating— kVA

Confirm availability, impedance and project standard with the manufacturer or utility

Coincident demand—

Required transformer capacity—

Transformer LV full-load current—

Minimum incomer current rating—

Minimum busbar design current—

Preliminary assembly rating—

Transformer-terminal fault—

Minimum withstand screening—

No result calculated.

Enter and verify all required project values.

Open cable sizing and voltage drop →Request an engineering review →

Important: Preliminary sizing only—not a final electrical design, protection study or certification. Verify network fault level, discrimination, harmonics, earthing, motor starting and equipment ratings.

Calculation basis

Demand, capacity and fault level
kept visible

Diversified demand

Each entered load group contributes coincident kW and kVA using its quantity, electrical input, demand factor and power factor.

Equipment capacity

Entered design margin, transformer loading, derating and busbar loading criteria determine the preliminary standard ratings.

Fault screening

Entered transformer impedance provides a transformer-only LV-terminal prospective short-circuit current and withstand screening value.

Transformer & MCCsizing

Define the electrical demand

Your details

Project

Load groups

Demand, capacity and fault levelkept visible

Diversified demand

Equipment capacity

Fault screening

Transformer & MCC
sizing

Demand, capacity and fault level
kept visible