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Carelabs

IEEE 1584 · Engineering

Motor Start Analysis Services in Italy | Carelabs Experts

Motor Start Analysis. A motor starting study calculates the voltage dip and acceleration time a large motor causes at startup, confirming your system can start it without nuisance tripping, excessive running current, or instability elsewhere in the facility. Carelabs models across-the-line, autotransformer, reactor, and variable frequency drive starting methods to recommend the right one for your load.

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Simulated, then measured

A starting study predicts what will happen. Commissioning verification establishes what actually happened. Where the two disagree, the model was wrong about something worth knowing.

What We Deliver

Prediction before procurement

Voltage dip, acceleration time and torque margin are simulated before the starting method is selected, so direct-on-line, star-delta, autotransformer, soft starter and drive are compared against the real load curve rather than by general preference.

WHY IT MATTERS

The simulation is not the commissioning record

Predicted and actual starts diverge when transformer impedance differs from the assumed value, when the driven load has more inertia than specified, or when supply conditions differ from the data provided. Each is worth discovering at commissioning.

  • Load speed-torque and inertia characteristics taken from the driven machine rather than assumed, since fans, pumps, compressors and conveyors behave very differently during acceleration.
  • Voltage dip assessed at every busbar, because a start that is comfortable at the motor can drop out contactors on an entirely different part of the installation.
  • Transformer impedance taken from test certificates where available, as typical values shift dip predictions materially on a weaker supply.
  • Repeated starting duty assessed where the process requires it, since thermal limits rather than electrical ones usually govern permissible restart frequency.
  • Standby generation modelled separately where present, as generator impedance produces a substantially deeper dip than the distributor's supply.
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DELIVERABLES

What you receive

Issued against CEI 64-8, with the simulated prediction and the measured result presented side by side.

  1. 1Predicted voltage dip at every busbar through the acceleration period
  2. 2Comparison of starting methods with the dip and torque consequence of each
  3. 3Measured start trace recorded at commissioning, retained as the installation baseline
  4. 4Reconciliation of prediction against measurement, with any divergence explained
  5. 5Protection settings verified against the measured starting current
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How the work runs

01

Collect motor and load data

Nameplate values, starting characteristics and the driven machine's torque and inertia data are gathered, since the load governs the outcome as much as the motor does.

02

Establish the supply

Source impedance is derived from the distributor's fault level and transformer data, because dip depth is a direct function of supply strength.

03

Simulate the start

The motor is modelled dynamically in ETAP and acceleration is simulated with voltage, current, torque and speed tracked throughout.

04

Select the method

Where the predicted dip is unacceptable, starting arrangements are compared on the same model so the recommendation rests on simulation rather than habit.

05

Measure at commissioning

The actual start is recorded at the motor and the busbar, producing the verified trace that becomes the installation's reference.

06

Reconcile and issue

Measurement is compared against prediction, divergence is explained, and protection settings are confirmed against what was actually recorded.

Frequently asked questions

Because the simulation rests on data that may be wrong. Transformer impedance, load inertia and supply strength are all frequently supplied as typical rather than actual values. Measuring at commissioning confirms the prediction or reveals which input was inaccurate, and produces a baseline trace that has diagnostic value for the life of the installation.
It is set by the most sensitive load on the affected busbar rather than by a single number. Contactors typically release somewhere below 70 to 80 percent of rated voltage and electronic equipment varies widely. This is why the study reports dip at every busbar rather than only at the starting motor.
No. It reduces starting current and therefore the dip, but it reduces available torque at the same time. On a high-inertia or high-breakaway load that can produce a start that is too slow or does not complete. Where torque is the binding constraint, a variable speed drive or a different motor selection is the correct answer.
Usually not, provided the supply and the driven load are unchanged. It becomes worthwhile where the network has been extended since the original installation, where the replacement is a different efficiency class with different starting characteristics, or where the driven machine has been modified since commissioning.

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