Are high inrush currents on startup causing damages in the transformer primary circuit ?

Switching ON the primary of an AC transformer can often generate high inrush currents. Applying electric power to the primary of a transformer can lead to more or less big troubles, especially if this operation is intended to be very frequent.

Frequent switching of the primary without adapted solution can lead to damages in the transformer primary circuit.

Inrush current can :

• cause the tripping of the circuit protection and the user may have to increase its current rating to allow a correct operation, leading to safety hazards with a bad coordination of the short circuit protection.
• damage the contacts of the mechanical contactors (arcing, welding because of the bounces at closing).
• damage the primary winding of the transformer especially if the switching frequency is important
• make mechanical stress in the wires and connections because of the magnetomechanical effect
  

Using celduc® relais SSR instead of contactor can improve considerably the switching operation but you should choose the right switching mode.

Our dedicated application note will help you to better understand the difference between :

SWITCHING A TRANSFORMER LOAD WITH STANDARD ZERO-CROSS SOLID-STATE RELAY

SWITCHING A TRANSFORMER LOAD WITH STANDARD RANDOM SOLID-STATE RELAY

SWITCHING A TRANSFORMER LOAD WITH PEAK STARTING SOLID-STATE RELAY

TO MAKE IT SHORT :

A peak starting Solid State Relay allows the starting current of the transformer to be reduced. So our SOP range with a peak control mode  is designed for the start-up of transformer primary circuits and all saturable inductive loads in order to avoid magnetising current peaks.

References available :
–SOP65070: 9A-AC56a
–SOP69070 : 32A-AC56a

SOP69070 can drive up to 32A transformers and is a very efficient control solution for small to medium transformers.

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