Case Study #204: How to Determine Amperage for Heaters

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Case Study #204

A customer called in and wanted to know what amperage he would be using on a machine with six heaters. The power supply was 460V, 3 phase power, and the heaters were wired in a delta configuration with two heaters on each branch. (See image below)

To Determine the Amperage:

6 heaters (R₁ – R₆) each at 230V, 1,000W

The resistance of each heater is calculated using the following formula:

R = V² / P

So, the resistance of each heater equals 230² / 1,000 = 52.9Ω

R₁ = R₂ = R₃ = R₄ = R₅ = R₆ = 52.9Ω

Now, we wire two of these heaters in series between two legs of 460V, 3 phase power. Each leg looks like:

In series, we can add resistances and simplify the circuit to look like this:

Now, finding the current is easy.

I = V / R
I = 460V / 105.8Ω
I = 4.35A

So, the amperage is 4.35A for each leg.

Have a technical question about a heating application? Shoot our engineering department an email today at engineering@thermalcorp.com.

Written by Jim Dixon and Shelby Reece
Edited by Kyle Otte
Date Published: 07.11.2019
Last Updated: 09.03.2019