Electrodynamic Shaker

Sdyn’s SEV and SEW series of Electrodynamic Shaker produces vibration based on the principle of magnetism. The SEV series is air cooled and SEW series is water cooled, respectively. The product portfolio covers all ranges of shaker, from 10 kgf up to 32000 kgf and beyond.

An Electrodynamic Shaker has two separate coils, one is stationary and the other is dynamic. A stationary coil or Field Coil helps in magnetising the iron to produce magnetic field lines and current flowing in the dynamic coil or Armature Coil interacts with these magnetic field lines to produce motion. This principle of magnetism is based on Maxwell’s Right Hand Rule and Fleming’s Left Hand Rule.

Major Sub Systems of the Electrodynamic Shaker are:

Armature Structure

Our armature features a web structure to minimise weight, while maintaining structural integrity. The pattern can only be casted, therefore, in order to achieve the best quality, we import these castings from one of the world’s most renowned sources. Complete tooling, milling, drilling, and tapping of these castings is performed in our in-house CNC centre.

The winding process is carried out at our headquarters in Roorkee, India. Special epoxy is used to ensure that the coils adhere to each other as well as the armature structure. Air cooled systems use a solid conductor and water cooled systems use hollow conductor with very heavy insulation.

For an air cooled system, power is transferred to the armature coil using highly flexible copper ropes. For a water cooled system, power and water are transferred on the same line using highly flexible copper ropes and hose pipes, respectively. Only oxygen free copper is used to ensure long life of the conductor.

Field Structure

The magnetic circuit design of Sdyn’s Electrodynamic Shaker uses two field coils. Housed inside the shaker’s body, the field coils are always stationary and produce a constant flux which magnetises the iron, creating the two poles in front and back of the armature coil. When AC power flows through the armature coil, interaction of its flux with the magnetic lines flowing between the two poles causes the armature to move. Copper rings are placed directly in the front and at the back of the armature coil with minimal space to cancel the eddy current.

The field coil is the primary source of heating inside the shaker as it is powered with a constant DC supply regardless of the test profile. In an air cooled system, these solid conductor coils are cooled by forced air which flows through the air gaps between the coils. In a water cooled system, these hollow conductor coils are cooled by water flowing inside the coils. To ensure proper cooling of the field coils in a water cooled system, both the field coils are built by stacking multiple disks of thin coils. These discs are connected in parallel for cooling and in series for power.

Suspension System

As the movement of the armature is based on magnetism, no physical contact is established with the shaker body. The armature is freely suspended in the air and without any suspension or auto centering system, it will sit at the bottom of the shaker. To achieve full displacement of the shaker, its armature should be centered. At Sdyn, we have multiple designs to center the armature based on customer specifications and test requirements.

Our standard design utilises four sets of rolling struts spaced 90 degrees apart. Rubber bush and cam bolt is assembled inside each rolling strut to create mechanical stiffness which keeps the armature centered. Our long stroke design utilises four sets of rockers spaced 90 degrees apart. Rocker offers no mechanical stiffness and the armature is centered via DC from the amplifier. Both designs also utilise an internal load support bearing along with an air diaphragm to assist in the centering process with heavy load mounted on the armature.

Isolation System

Our shakers are capable of producing vibrations over a wide range of frequencies at high g levels. These vibrations are produced on the armature head from where they are transmitted to various attachments and fixtures depending on the test. However undesirable it may be, a certain part of these vibrations are also transferred into the body of the shaker. It is necessary to isolate these vibrations in the body of the shaker from its base. This is achieved with a complex array of air bellows and spring placed between the shaker and its base.

For further isolation, air bellows are attached to the bottom of the base or the combo base in case of a system with a Horizontal Slip Table. As a result, all system supplied by Sdyn can be installed in a multistory building as their is negligible dynamic weight due to vibration in the shaker body.

Cooling System

It is not possible to run a shaker reliably without proper cooling because the extensive heat produced inside the shaker can damage the armature coil. Small shakers (50kgf and below) generally feature a permanent magnet instead of a field coil, therefore, they can operate without any cooling at light loads. A similar feature can also be offered with bigger systems to meet certain test requirements like Squeak and Rattle test being performed on an air cooled shaker.

A shaker can either be air cooled or water cooled. Each method has its own key features, advantages, and disadvantages. Selecting a cooling method that meets customer’s test requirement is crucial. Both these methods are breitling replica discussed below:

An air cooled shaker features a centrifugal blower for forced air cooling. A hose pipe connects the bottom of the shaker to the blower which sucks air from a perforated sheet at the top of the shaker. It is very important to ensure that the blower is not located in close vicinity of the shaker because this might cause the exhaust air from the blower to be sucked back by the shaker. In this scenario, the shaker’s temperature will keep increasing as it is being cooled by the same air in a loop, causing thermal runaway and even burning of the armature coil. To ensure safety and proper operation of the cooling system, various sensors are installed in the shaker that are mentioned below:

Air Pressure Sensor – To ensure sufficient air pressure for proper suction
Air Temperature Sensor – To stop the system if the air temperature is too high to ensure proper cooling

Due to suction, audible noise is always present near the shaker and the blower. It is suggested to take measures during installation to prevent this audible noise from creating an un-conducive working environment for the test/ lab personnel.

Water Cooling Method

A water cooled shaker features a dedicated cooling system for storing, circulating, and cooling distilled water that is used for cooling. The system is assembled in two 19-inch racks of 42 unit height. Pressure pump is installed in the cooling rack to circulate distilled water at high pressure through the shaker’s field and armature coils. Heat exchanger is installed in the cooling rack to cool this distilled water with another supply of water from a cooling tower or chiller at the customer’s site. To ensure safety and proper operation of the cooling system, various sensors are installed in the cooling racks that are mentioned below:

Liquid Pressure Sensor – To measure the water pressure in the pipes in order to detect any obstruction in the pipeline
Liquid Flow Sensor – To measure the water flow in the pipes in order to detect any leakages in the pipeline
Liquid Temperature Sensor – To measure the temperature of the incoming and outgoing water in order to detect overheating

Technical Specifications