Technology

Blowout Magnets - What They Are & Why Use Them?

The one big problem facing anyone switching a high current DC load is how to turn off the arc which is generated when the switching contacts open. By comparison, switching AC is easy, the arc is self-extinguishing every time the waveform crosses zero which happens several times, depending on the AC frequency, whilst the contacts open and move apart.

Contact Resistance Versus Contact Pressure

The relationship between contact resistance & contact pressure explored. This paper seeks to simplify the wealth of information available (mostly highly detailed equations) from learned papers & publications & discusses relevance to the everyday application of electro mechanical relays. The basis is that as contact pressure increases, contact resistance decreases.

Contacts - Their Construction & Materials

A simplified overview of the construction of contacts and the materials they are made of, including common materials we use in Durakool relays to manufacture reliable high quality relays. Key features of those materials together with application information as to where and where not those materials are suitable to be used are also included in this helpful document.

EV Battery Charging Applications - Relays & Contactors

Electric vehicles, in one form or another, have been around for over 100 years. Early vehicles used lead acid batteries and worked at 6V and upwards. Lead acid EV’s are still around in the 21st century in large numbers (think forklift trucks or golf carts, for example) but Lithium based batteries are replacing them, especially in applications such as cars, vans and trucks.

How to Avoid The Most Common Relay Problems

Do you know how to avoid the most common relay problems?

Everything begins with really knowing your application before you select a solution! With solid information about the 8 factors to consider, the Durakool team can guide you to the most robust and efficient solution available.

HVDC Contactors and Failure Modes

A useful Durakool technical presentation regarding correct and incorrect HVDC contactor positioning. Typically an electric vehicle (EV) will have two main contactors positioned in the feed from the battery to the electronic motor drive. There may be others used as part of the pre-charge, discharge or charging circuits. The principle function of the main contactors is...

HVDC Relays & Contactors Conductor Size & Heat Dissipation

A presentation by John H Merrill providing information regarding HVDC Relays & Contactors Conductor Size & Heat Dissipation, commencing with the principles of DC switching and detailing terminal temperature conditions best taken into account when selecting the correct product for your application and the environment in which it is to be used.

HVDC Relays & Contactors Overview

A helpful overview of Relays and Contactors including, DC switching considerations, information on Paschen's law, the principles of DC switching and when DC currents and voltages are high enough, details of arc extinguishing and how to stop the arc from forming, terminal considerations and the design of relays and HVDC contactors.

Durakool Latching Relays

A technical note explaining in detail, Durakool latching relays and contactors (electro-mechanical relay/contactor with contacts that are stable in two positions without voltage applied to the coil – “Bi-stable Relay”). Voltage is applied to the coil only to enable the contacts to change state – the coil does not have to be energised for the contacts to stay in either position.

A Layman's Guide to Coil Suppression

Why it is common practice to put a diode in parallel with a relay coil and importantly, the effect this has on the relay’s performance. Are there suitable alternatives? A two page guide designed to help would be users to be aware and to avoid potential pitfalls which could be costly and time wasting if unarmed with correct information.

Relay Contact Forms - An Explanation

Over many years different short forms describing contact arrangements used by switches, relays and contactors have evolved.

This technical document lists a number of the most common variants, using a diagram to assist with  understanding the various contact arrangements (contact forms).

Switching Polarised and Non Polarised DC Contactors

This technical document is a six page presentation by John Merrill, one of The Durakool Team, in which John has detailed key information regarding the switching of polarised and non polarised DC contactors. The document explains the DC contactor structure and working principle together with the arc extinguishing system.

Temperature & its effect on Electro Mechanical Relay Operation

A three page technical document highlighting how failure to understand or make allowances for the effects of temperature on electro mechanical operation can lead to the relay failing to operate when called to do so, or worse, the premature failure of the contacts! A much neglected and misunderstood area in the application of electro mechanical relays.