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# Motor Voltage Drop Calculator (MS Excel Spreadsheet)

## Motors up to 500 HP and 575 Volts

This program calculates voltage drop caused by the starting of motors at the substation transformer primary and secondary leads. Primary system impedance and transformer impedance is taken into account.

Secondary conductor impedance is not. Calculator allows use of a autotransformer reduced voltage starter and provides calculations based on tap setting.

Two calculators are provided. One is based on tables 430-150 & 430-151(B) from the NEC. The tables provide current ratings for motors up to 500HP and 575 Volts.

The other allows full use of motor nameplate data.

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1. Very enjoyable please I like it EEP
Sep 17, 2020

South Sudan electricity corporation,Juba, power plant

2. RAMESH KUMAR KAPUR
Mar 18, 2020

Besides, the suggestion of Chirantan Gupta, Sourse is considered to be infinite, which is not the case always, threfore, Transient Reactance or Transient impedence of the Source also shall be considered to arrive at voltage drop. If all these parameters are considered then the drop will not be limited to rating of the motor/or small motors

3. Benrouissi Ismail
Oct 29, 2017

4. Chirantan Gupta
Apr 15, 2014

There are some vital improvements required. Firstly, the Transformer impedance should have a facility for +ve tolerance of 7.5% since this calculation is mostly done at early stage, when Transformer procurement and testing has not been conducted. Secondly, the cable length and size is required in the mathematical model. Otherwise, we will never know the voltage drop at the motor terminal box. Thirdly, the remaining base load on the bus also needs to be modeled, since this affects the Transformer regulation and the violtage drop.

• Jimuel Medina
Sep 17, 2021

I believe this was modeled in a way that the regulation of transformer and its tap were already identified. I think this is something the author of this article must need to mention in this particular subject.

I think this calculator is good, you just need to know its limitation and youâ€™ll just apply it based on limitation this can be used to.