- 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 been connected.
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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Where is Supply Monitoring Relay Used?
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CNC / VMC machines
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Induction motor panels
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Compressor panels
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HVAC systems
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Distribution panels
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Lift and elevator control panels
Features of SM175
- 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 SM175
- 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 for supply monitoring device SM-175
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.
FAQs for supply monitoring relay SM-175
Q1. What is a supply monitoring relay?
A device that protects equipment from phase failure, phase reversal, over-voltage, and under-voltage.
Q2. Can SM175 work on single phase?
No, it is designed for 3-phase systems only.
Q3. What happens during phase failure?
The relay trips within milliseconds and disconnects the control circuit.
Q4. How to set under-voltage and over-voltage?
Set the reference voltage first, then adjust UV and OV percentage knobs.
Q5. Where is this relay installed?
In control panels to protect motors, machines, and sensitive equipment.
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.
Hi, if my line voltage is 240v, will it function
Do I calculate the ov and uv % 240v or 220v
Yes, This will work for line to line voltage upto 208 Volts. But this device does not meant for 240 volts single phase system !
Yes, this device functional for the range 208 to 480volts. You can set the voltage range & adjust the UV% & OV%.
This device does not meant for 240 volts single phase system !
could you please me the connection diagram
As described in a post above; L1,L2 & L3 are the 3 phase input terminals where 3 phase power is going to be connected while for signal a changeover relay been provided with 15,16 & 18 terminals in which 15 is common, 16 is NC & 18 is NO.
can you provide me the pCB circuit diagram for this device
Do you means printed circuit diagram ?