- Every Electrical device has defined voltage range in which device works precisely & provides maximum efficiency. That’s why voltage must be balanced & stable inside the range.
- Voltage out of the range can produce unwanted losses in the form of heat, vibration & sound. In worst cases it can damage the device.
- Stable & balanced voltage is also the first priority in Electronics, voltage variation can damage the whole circuitry.
- In 3 phase induction motor the direction of rotation can be changed by just interchanging 2phases connected to the motor. A specific task needs specific direction of rotation. Hence, Reversal of direction leads to an unwanted & dangerous situation. Direction of rotation is also very important. Supply sequence shouldn’t be changed at any cost that’s why phase reversal protection is also very important.
THAT’S WHY Protection from unbalanced voltage, phase loss, & phase reversal is very important. This is the reason, In special machines like CNC,VMC & even in main distribution panels supply monitoring devices are being provided.
In this post, we are going to discuss supply protection device that is Gic make Series-SM175 & CAT.No.MD21DF.
Supply monitoring device SERIES-SM175; CAT.NO.MD21DF
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Features of the Device
- Monitors sequence of 3phases & provides protection from phase reversal, & phase failure.
- Provides protection in Under Voltage & Over voltage scenario with Adjustable Undervoltage & Overvoltage range.
- LED Indications for all the faults.
- Adjustable time delay for fault condition.
- for Error signal, 1 changeover relay is provided.
- Easy knob setting for voltage adjustment
Specifications of the device
- Supply Voltage (Un): 208 to 480VAC, 3phase 3wired
- Frequency : 47 to 63 Hz
- Power Consumption: 3VA(max.)
- Operating Temperature: -15°C to +60°C
- Storage Temperature: -20°C to +80°C
- Dimensions (mm): Width× Depth× Height (18×59×90)
- Weight: 70 grams(approx.)
- Degree of protection: IP20 for terminals| IP30 for housing
- Mounting: Base/DIN Rail
- Changeover Relay: There is 1 relay with 1NO & 1NC points, Contact rating is 5Amps @250 VAC/30VDC
- Release time/trip time: (for under-Voltage & over-voltage)- 0.5 to 15 sec. Selectable// Release time is the time which starts when supply crosses the permissible limit, After completion of release time relay operates.
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Phase reversal time: <65msec.
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Phase loss time: <65msec.
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LED Indications:
- Healthy- RV led continuously ON
- Phase Reversal- RV LED Flashing
- Over Voltage- Over Voltage LED continuously ON
- Under Voltage- Under Voltage LED continuously ON
- Phase fail- All LEDs are OFF
Trip level
There are four knobs are provided. Upper most knob is reference voltage knob(Un). 2nd & 3rd knobs are limits knob for Under-Voltage & over-Voltage respectively. These knobs are percentage knobs, it takes percentage of reference voltage.
Under Voltage (-2to-20% of Un), Over Voltage (2 to 20% of Un), Phase loss- Yes, Phase Reversal- Yes (Un= selected/reference voltage )
For example
Let suppose reference voltage is set on 400 Volts. Under-Voltage & Over-voltage both the knobs are set on 5%.
5% of 400=20
@ Upper limit for Overvoltage becomes,
400+20=420
@ Lower limit for undervoltage becomes,400-20=380
Last & fourth knob is release time knob. Which is been described next.
Connection Diagram
3 phase power supply Red, Yellow & Blue are connected to L1,L2&L3 respectively. There is no need to connect extra auxiliary supply to the device.
Single relay is provided at bottom of the device. Relay’s 3 contacts Common, NO & NC are provided on the device where 15 is Common, 16 is NC & 18 is NO.
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Merits of the Device
- Compact in size with DIN rail mounting.
- Voltage limit can be set easily with provided knobs.
- Operating time is also adjustable.
- No extra Auxiliary supply needed for the Device.
Summary
Supply monitoring devices are special devices which are utilized to monitors the line voltage. On phase loss, Phase reversal, undervoltage & overvoltage conditions these devices are utilized to get an alarm or trip out the system. There are multiple types of voltage monitoring devices equipped with multiple functions & features. But basic function remains the same Which is easily be understandable through this post.
Hope! You like the post. If you have any doubt, suggestion or query please do comments.
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