Difference of smart motor protector and thermal relay-Compere

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Difference of smart motor protector and thermal relay

Release time：2018-12-27 ~~Times of browsing：~~

The development of motor protection device is also integrative with the development of technology. Now, the widely used motor is developed from traditional thermal relay, and the thermal relay as the traditional protection device is still widely used.
So, what is the difference between intelligent motor protector and thermal rely in application?

The thermal relay has a single function, and it has the defects of poor repeatability and inability to be used again after the failure of large current. However, it is widely used due to its low price and simple structure.

The intelligent motor protector has various functions compared with thermal relay, and can be used repeatedly, the action is sensitive and the measurement accuracy is high. However, the price of smart motor protector is relatively higher than other motor protection devices., and the initial purchase cost of adopting the smart motor protector to protect motor is higher too.

However, in the long run, the overall cost that adopt smart motor protector is the lowest.

Comprehensive comparison between intelligent motor protector and the thermal relay:

Item	Motor protector	Thermal relay
National policy	Continuously promote and apply energy-saving product	Eliminate outdated models
Principle	Integrated circuit	Machinery, heat principle
Protect process	Electrical signal transmission and electromagnetic action	Heat transmission, Mechanical action
Protect function	Loss phase, stall, blocked, overload inverse time protection, start overtime, phase sequence protection, three phase unbalance, short circuit, heat accumulation overload, underpowered, overvoltage, leakage, temperature, analog input, external fault, contactor break overflow, TE time, etc.	Loss phase, stall, blocked, overload inverse time protection
Measurement function	Measure the voltage, current, power, energy and frequency	No
Control function	On site, remote, bidirectional, start triangle, Self-coupling reducing voltage, anti-shaking start, no-voltage restart	No
Reliability	Electronic components. high repeatability, high accuracy, high reliability	Dual-metal piece, easy aging, inferior repeatability, accuracy, reliability.
Reflect time	Fast, action in time, can be set according to the customer requirement.	Slow, protection is not timely
Recovery time	Fast, can be set according to the customer requirement, can reach millisecond level	Slow, manual two minutes, automatic five minutes.
Price	Relatively high	Relatively low
Annual cost	Max. power 5W, annual electricity bills are about $7	Min. Power 60W, annual electricity bills are about $90
Security	Serialize to circuit, low safety factor	Parallel to circuit, high safety factor
Communication	Modbus, Profibus, RS485	No
Application occasion	High protection requirements for industrial automatic occasion	No need system integration, low protection accuracy for small power field.
Overload requirement	Solid, liquid and gas load	Solid load, load flat
Installation position	No special requirement	No vibration, no heat source, dispose of the installation below.

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