Calculate before you draw
Calculators we use ourselves. No registration, no data sharing — your entries never leave your browser. Each one states the formula and the assumptions behind it, so you can verify the result rather than trust it.
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A guide, not a design to standard. We give no warranty for the correctness of the results, the applicable standards and case-by-case verification govern.
Cables and installation
- 01Cable cross-sectionThree-phase: A = (√3 · L · I · cos φ) / (κ · Δu)
- 02Voltage dropThree-phase: Δu = (√3 · L · I · cos φ) / (κ · A)
- 03Cable resistanceR₂₀ = L / (κ · A)
- 04Cable lossesThree-phase: P_v = 3 · I² · R
- 05Maximum cable lengthThree-phase: L_max = (Δu · κ · A) / (√3 · I · cos φ)
- 06Current-carrying capacityI_z = I_z0 · f_temperature · f_grouping · f_other
- 07Parallel cablesA_total = n · A
- 08Conductor temperatureϑ_conductor = ϑ_ambient + (ϑ_max − 30 °C) · (I_B / I_z)²
- 09Cable capacitanceC = C′ · L
Short circuit and impedance
- 10Short-circuit currentIᵣ = Sᵣ / (√3 · Uᵣ)
- 11Cable impedanceR = L / (κ · A) · [1 + α · (ϑ − 20 °C)]
- 12Network impedanceFrom power: Z = c · U² / S_k″
- 13Short-circuit current at the far endZ_loop = Z_upstream + R_L + R_PE
- 14Thermal short-circuit withstandA_min = I_k · √t / k
- 15Length and disconnectionZ_max = c · U₀ / I_a with U₀ = U / √3
Motors and drives
- 16Motor currentThree-phase: I = (P / η) / (√3 · U · cos φ)
- 17TorqueM = 9550 · P / n (P in kW, n in min⁻¹, M in Nm)
- 18Starting currentI_A = I_N · (I_A / I_N)
- 19Star-delta startingI_A(delta) = I_N · (I_A / I_N)
- 20Soft startingI(U) = I_A · U / U_N
- 21Motor efficiencyP_in = P_out / η
- 22Speed control instead of throttlingFlow: Q ∝ n
- 23Speed and slipn_synchronous = 60 · f / p
- 24Setting the motor protectionDirect on line: I_e = I_N
- 25Single-phase motorP_in = P_out / η
- 26Motor feederP_in = P_out / η
- 27Required motor ratingP = M · 2π · n / 60
Protection and discrimination
- 28PFD and SILPFD = PFD_sensor + PFD_logic + PFD_final element
- 29PFH and SILPFH = PFH_sensor + PFH_logic + PFH_final element
- 30Protective conductor sizeThermal: A = I · √t / k
- 31Earth rodR = ρ / (2π · L) · ln(4L / d)
- 32Touch voltageU_B = I_fault · R_return
- 33Residual current protectionI_leakage = n · I_device + I_cabling
- 34Check discriminationOverload: I_n(upstream) / I_n(downstream) ≥ factor
- 35Connecting a surge arresteru = L · di/dt
Power quality and compensation
Calculating is the easy part.
A formula gives you a number. Designing a plant also demands installation method, grouping, discrimination, the standards in force and a look at the installed base. That is what we take on.
Contact
Tell us what it is about.
A phone call or three lines is enough. From the very start you talk to the people who will later work on your project, not to a distribution list.
Direct
- Phone+49 (0) 5247 4070-66
- Emailinfo@fisekon.com
- AvailabilityMon – Fri, 8:00 – 17:00 CET
Locations
33428 Marienfeld (Harsewinkel)Gütersloh officeWagenfeldstr. 2
33332 Gütersloh
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