To determine the required transformer VA, multiply the secondary voltage by the required amperes: For example, VA=Volts x Amperes or 28V x 1.2 amperes = 33.6 VA. To determine the maximum transformer current, divide the transformer VA by transformer secondary voltage.

Step-Down transformer If the primary is 500 volts, we will get 50 volts at the secondary. This is referred to as a Step-Down transformer. They are most commonly used in control circuits where the motor voltage is 480V, 600V, or higher. The step-down control transformer would reduce the voltage to pushbuttons or PLCs to 120V or even 24V.

Selection StepsDetermine your primary (source) voltage (V)Determine your secondary (control) voltage (V)Calculate the total amount of VA drawn from your control circuit by determining the Application Inrush VA by using the following industry-accepted formula: Application Inrush VA = √(Inrush VA)^2 + (Sealed VA)^2.

A control transformer is required to supply voltage to a load which requires significantly more current when initially energized than under normal steady state operating conditions. A control transformer is designed to provide secondary voltage stability under a short period of specific overload referred to as inrush.

Industry standard sizes for 480- to 120/208-volt wye transformers are commonly 15, 30, 45, 75, 112.5, 225, 300 and 500 kilovolt-amperes. There are also single-phase 277-or 480-volt transformer sizes available at 5, 7.5, 10, 15, 25, 37.5, 50, 75 and 100 kilovolt-amperes.

Operating at a higher frequency has many benefits, the first of which is size. For any given power rating, the higher the frequency, the smaller the transformer can be. Second, because the transformer is smaller, less copper wire is needed, thus reducing the losses and helping to make the transformer more efficient.

A transformer is an electrical device that trades voltage for current in a circuit, while not affecting the total electrical power. Transformers can be used either to increase the voltage also known as stepping up the voltage, or they can decrease the voltage also known as stepping down the voltage.

## What is the minimum safe distance from power lines?

10 feet Work at a safe distance This is the most important rule: Work at a safe distance from all power lines. The Occupational Safety and Health Administration (OSHA) requires that equipment be kept at least 10 feet away from power lines with voltages up to 50kV.

For a 200 A at 120 V single-phase service, the apparent power is 48 kVA. A 50 kVA transformer wont be installed by the utility. Standard sizes of single phase transformers are 5, 10, 15, 25, 37.5, 50, 75, 100, and so on.

Effect of frequency The EMF of a transformer at a given flux increases with frequency. By operating at higher frequencies, transformers can be physically more compact because a given core is able to transfer more power without reaching saturation and fewer turns are needed to achieve the same impedance.