Directory for Selecting Relay Types For correct use of relays you have to understand on what conditions you are going to use the relays and know how to select proper ones. Sometimes the contacting points, coils and environmental conditions of the relays are very important. Following points of characteristics and notes will be helpful in selecting right relays. The most important points are listed below for selecting right relays: (A) Consideration of the coil part 1. Are you going to use DC or AC to the coil? 2. The shape of the wave of the voltage which will be added to the coil 3. Manner and current of magnetic excitation The necessity of special magnetic exciting current 4. Impedance of the coil Action and release voltage (B) Consideration of the contacting points 1. Types and group number of contacting points 2. Loads of the contacting points AC or DC loads? Is it resistant load or inductance load, or capacitive load, or combined one? Is there any counter-electromotive force or impact current? 3. Contact points loading level How big is the current, and the current load will be connected or not? 4. Action switching frequency 5. Requirement for electrical action times (C) Environment 1. Environmental temperature and humidity ranges 2. atmosphere environment 3. Vibration and impacts (D) Insulation 1. Strength to high voltage 2. Insulation resistance (E) Installation 1. External sizes 2. Terminal installation and welding 3. Ways to install (F) Others 1. Weather Safety standard and/or other standards required? 2. Weather there are special characteristics or conditions?