A high voltage DC relay is an electromechanical device that switches high voltage DC current on and off repeatedly using low voltage.
This process protects your electrical equipment from damage, fire outbreaks, short-circuiting etc.
High voltage DC relays are normally designed as open. The electrical current energizes the coil which pulls the plunger.
Different DC relays have varied current and Voltage ratings. The bottom line though is that they have become major components in various modern equipment. They convert DC power to any of the required loads with optimized efficiency and performance.
Hotson offers different high voltage DC relays with unique capabilities and features. These take from a few tens of current amperes and voltage up to thousands. Also, there are different sizes depending on your application ranging from small handheld devices to complex ones for superior purposes. 

When the electric current passes through the relay, the electromagnet establishes a strong magnetic field.
The field pulls the armature into the copper coil creating an electrical arc. Then, the electrical currents flow into the device in which the relay is mounted.
When there is no current flow, the spring pushes the armature, breaking the connection. The switch performs the primary role of a high voltage DC relay by continuously turning the current ON and OFF. 

• Electrical vehicles (EV)                     
• Photovoltaic
• Wind power systems                           
• Energy storage systems such as CPU
• EV DC battery charging stations       
• Lighting 

We use two main technologies for our hermetically sealed high voltage DC relays. These are ceramic and epoxy.
The ceramic high voltage DC relays are filled with hydrogen whereas epoxy is filled with nitrogen gas.
We use these two technologies to eradicate extreme relay discharge. When the arc forms, it can never extinguish on its own. The continued arching means damage to the contacts. To extinguish arching, we adopted a gas filling technique.
The gas required for this purpose must be very active and have a stable molecular structure.
The hydrogen gas possesses all the above characteristics hence its use in ceramics. However, owing to the small molecular weight of hydrogen, epoxy cannot properly seal it. That’s why Nitrogen is preferred for epoxy sealed DC relays.
Examples of ceramic sealed high voltage DC relays include; EVH400, EVH300, EVH250 etc.
Epoxy sealed high voltage DC relays include; EVQ 10, EVQ 30 and EVQ 50.

If you’re looking for high voltage DC relays, you should know that it’s not a one-size fits all. Different high voltage DC relays have different uses and needs. Ensure you know exactly what you’re looking for to avoid inconveniences.
Generally, consider the following factors before buying your high voltage DC relays:

• Reliability
• Safety
• Compactness
• Lightweight
• High voltage cut-off
• Current rating of the load
• Voltage rating of the load
• The type of load
• Latching operation
• Compatibility

1. Reliability 
They have good working characteristics and low failure rate under all operating conditions. They have large contact surfaces which reduces the current interruption caused by loose contacts. They have quick operational characteristics which reduces sparking when the switch is operated. Reduced sparking helps to reduce wear and tear thereby minimizing the operation cost and increasing the lifespan of the relay.
2. Safety 
Safety is paramount in the operation of all electrical components. DC Relays are designed with an enclosure made of insulating material such as Bakelite, nylon and thermosetting plastics to insulate and protect the contacts and the machine operator. Safety is therefore ensured due to inherent safety design.
Our high voltage DC relays are very stable and can be used even in harsh environments. They can operate under extreme temperatures between -400c and 85+0c.
3. Compactness
Modern designs of high voltage DC realys are more robust and efficient. The individual components are closely packed hence reducing the overall cost of the relay making them cheaper.
4. Lightweight
Your high voltage DC relay should be small in size and does not produce noise during current transmission or switching.
5. High voltage cut-off
DC relays come in many forms with varying capabilities and features. They range from having the breaking current of several amperes to thousands of amperes. This makes them applicable in almost all electrical circuits depending with the load requirement of the circuit
6. Current rating of the load
The current rating of the load determines the size of the relay to be selected since different loads have different ratings. Small loads will go with small rated relays while large loads need high rated relays. Any attempt to violate this rule will lower the efficiency of the relay or damage the relay completely.
7. Voltage rating of the load
The higher the voltage, the higher the sparking. Each high voltage DC relay should be operated  at its designed voltage to avoid damage. Our relays can switch high voltages ranging from 12V to 1500V and currents from 10A to 600A.
8. The type of load
Three-phase relays should be connected to three-phase loads while single-phase relays to single-phase loads 
9. Latching operation
A relay with high latching speed is good because it minimizes sparking and reduces wear and tear of the contact surfaces.
10. Compatibility
The relay should be compatible with other electrical components in the circuit for their maximum performance. These components include the power control system; like, mechanical interlocks, bus bars, thermal overload relays and motor protection circuit breakers. 

They don’t have hysteresis losses and therefore no power loss associated with their operation. Hysteresis loss is caused by alternating current as it alternates between the positive and negative maxima through zero line.

• Have high voltage cut-off and high current cut-off making them suitable for all industrial and domestic purposes.
• Enables the operator to control a remote located machine without necessarily going near the machine.
• They are not affected by high temperature hence suitable for industrial application and in places where machines experience high temperature during operation

If your high voltage DCrelay stops working or doesn’t start at all, trouble shoot in the following ways.

• Ensure that the coil is not broken or damaged since a damaged coil will stop the operation or reduce the efficiency of the relay.
• Check the voltage level of the supply system to ensure that it is correct. Low voltage and fluctuating voltage will hinder the optimum functioning of the relay.
• Checking whether the pressure of the contact spring is high enough to break the circuit when the power is switched off.
• Ensure the contacts do not stick together.
• Ensure the coil receives power when the current is switched on. 

Since high voltage DC relays play a big role in electrical circuits , it is important to ensure they are serviced regularly to prevent them from failing suddenly during operation. For good performance and high efficiency, ensure that they are in good working condition before they are installed in the circuit. Also, ensure that the IEE regulations regarding the use of relays are followed.