DENT Instruments RōCoil TCA-5™
Contents
1. Unclipped sinewave Clipped sinewave Figure 3 2 RoCoil Clipped Waveform TIP Use a true RMS DVM to measure the voltage across the output terminals of the ROCoil TCA 5 A voltage above 250 mV RMS indicates that the signal may be clipped Integration The RoCoil TCA 5 employs an internal precision analog integrator to compensate for the phase angle produced by the RoCoil current sensor vector 4 For this reason the TCA cannot be used with a 333mV split core current transducer unless the phase information is not needed Frequency Selection The RoCoil TCA 5 has been specifically designed and calibrated to work with 50 and 60 Hz circuits The 50 60 Hz slider selects one of two small angle correction vectors and inverting vectors 5 and 6 bringing the amplifier phase within 0 1 degree of the reference conductor phase If the incorrect frequency is selected a phase error of 0 6 degrees will result The sensitivity of the phase to frequency is approximately 06 degrees per Hz The R Coil TCA can be used on portable generators where frequency is not well regulated Consult DENT Instruments for use of the ROCoil TCA 5 on 400 Hz circuits Performance The ROoCoil TCA 5 can be supplied with RoCoil flexible current transformers purchased separately The combined errors of the TCA used in conjunction with supplied CTs is typically better than 1 1000 A 10A 1000 A 2500 A 25A 2500 A 5000 A 50A 5000 A Table 3 1 Min Max Curre2. AC voltage used to power the TCA 5 and power meter from the RoCoil signal conductors by running them in separate conduits as shown in Figure 2 1 The ROCoil signal shield wires should be terminated at the ROCoil TCA 5 end only December 13 2013 7 DENT Instruments RoCoil TCA 5 Powering the TCA 5 The TCA 5 operates from 48 volts DC 10 and has a full power consumption of 30 watts The DC connections are made in the lower right hand corner of the unit inset image The DC connection is polarity sensitive and will only power up if applied with the correct polarity Backwards polarity will not damage the unit but it will not turn on DENT Instruments offers two DIN rail mounted AC DC power supplies for line powering High voltage 200 500 VAC and Low voltage 100 240 VAC The High Voltage model is suggested for all three phase power systems and the Low Voltage model is suggested for single phase residential customers In both cases the AC DC power supply input is connected between two phases of incoming voltage DENT Instruments recommends powering the AC DC power supply through a dedicated breaker to avoid the use of tap rules whenever space allows as shown in Figure 2 1 If the TCA 5 is powered from an auxiliary control transformer rather than directly from line power ensure that the transformer has 30 VA of available capacity DENT Instruments 8 i NSTRUMENTS 30W m A i Eee me ee A J 00060
3. Inverting Summer 4 Phase after Integration 5 Phase Adjust 6 Conductor Phase Calibration Pa Phase Adjust JE Calibration Conductor 5 G Phase a Figure 3 1 RoCoil TCA Vector Diagram Range Selection The RoCoil TCA 5 range selection slider switch selects the primary gain of the amplifier Internal feedback with gains of 1 2 5 and 10 are selected using laser trimmed precision resistors within an inverting precision operational amp circuit shown as vectors 2 and 3 in Figure 3 1 The Current Range Selector is normally set to the nearest value over the size of the breaker feeding the load being measured For example the 1000 amp setting would be used with an 800 amp service breaker If the size of the load is known to be much smaller than the service capacity better accuracy can be obtained by selecting the range closest to the actual usage If the actual current is higher than the selected range the RoCoil TCA 5 waveform will be clipped and will not give an accurate reading The effect of clipping the waveform is illustrated in Figure 3 2 December 13 2013 13 DENT Instruments R Coil TCA 5 Severely clipped waveforms resemble a square wave Ensure that the selected current range of the meter is above the current flowing in the measurement circuit to avoid this condition NOTE The R Coil TCA 5 will not be damaged if the output is over ranged and Vp lt V Vr gt Ve is clipping
4. the CT Orient the CT so that the arrow on the CT connector points in the direction of conventional current flow toward the load Source Figure 2 5 RoCoil Connectors Push the connector back together with the conductor within the loop of the CT Mark and route the ROCoil signal wires to the ROCoil TCA 5 Figure 2 6 Signal Wire Identify and terminate the signal wires for connection to the ROCoil TCA 5 White Brown Bare Table 2 1 Connection Color Code The output connector polarity is marked on top of the enclosure Output connections should be tightened to 0 8 Nm 7 in lbs to ensure a low termination impedance Avoid routing the output wires in close proximity with the signal input wires to avoid introducing feedback Both the input and output circuitry are tolerant of plugging and unplugging under load without damaging the TCA DENT Instruments 10 December 13 2013 R Coil TCA 5 OUTPUT IMPEDANCE BURDEN The R Coil TCA 5 is a bipolar push pull current source that operates internally from a 1 0 volt DC power supply The design senses the output current using a precision resistor and drives a pair of MOSFETS through a feedback loop to control the current Linearity and precision is maintained as long as the requested current can be delivered within the voltage compliance of the DC supply The fraction of voltage drop allowed by the output circuity i e the voltage loss due to current flowing through the
5. 0 iT Figure 2 2 DC Connections December 13 2013 R Coil TCA 5 Where enclosures are required to protect the RoCoil TCA 5 from exposure to the local environment the following graph courtesy of Hoffman Enclosures provides an indication of the smallest allowable enclosure size The internal enclosure temperature cannot be allowed to exceed 60 C 140 F if full 1 current is demanded from the RoCoil TCA 5 An enclosure having a surface area of 3 square feet or larger is recommended for a typical design case 20 C temperature rise 20 watt internal load 6 7 watt square foot 75 The RoCoil TCA 5 can be mounted as a panel unit using the slide out tabs on the back or mounted on a 35 mm width DIN ea Figure 2 3 Top hat EN 50022 Rail Sealed Enclosure Temperature Rise Ambient F MJ QU Oo lt q QU oe QU 2 mur p wv CL Temperature Rise Above Ambient C 4 6 8 10 12 14 16 Input Power Watts Square Foot Unfinished Aluminum and Stainless Steel Enclosures Painted Metallic and Non metallic Enclosures Figure 2 4 Sealed Enclosure Temperature Graph December 13 2013 9 DENT Instruments R Coil TCA 5 Connecting Current Outputs 1 2 3 4 5 Open the CT by squeezing the connector latch and pulling it apart Connect the CT around the conductor to be measured Make sure no other conductors are within the loop formed by
6. DENT Instruments RoCoil TCA 5 5 Amp Transconductance Amplifier a r 7 en 7 Po a Fi Fi Fi EL a E g igg eee eee Pome a D _ _ _ _ _ Operator s Guide R Coil TCA 5 Operator s Guide ROCoil TCA 5 2013 DENT Instruments Inc All rights reserved This manual may not be reproduced or distributed without written permission from DENT Instruments Trademarks RoCoil and RoCoil TCA 5 are trademarks of DENT Instruments Inc DENT Instruments 925 SW Emkay Dr Bend Oregon 97702 USA Phone 541 388 4774 Fax 541 385 9333 www DENTinstruments com DENT Instruments li December 13 2013 Table of Contents INTRODUCTION Product DOS CHAOS een a a den aerate SCI TIGA CON seceosnsaticabernedectapatnedGensnees sane tesuetnoeseunamay e Sek FES UI LR ARE SE RS Re ede FIELD INSTALLATION Powering the TCA 5 wisi screassisecsssnnnesannakcossseannossstobsodenieaevaeneeasousneessstonsebanduesess Connecting Current Outputs sise Output Impedance Burden ssssssssssseesesssssrrrrrrrrrrrrrereeessssssrrrrrrrrrreeee THEORY OF OPERATI ON OBS A E N E AN PRINS SS CIS CUO ressis recne ier NENE s E ai ES SV AO eer S E lotion domi Reden SE 16 ON esnan PELTON 1 0 2 A LE descinedineeueniieseeis FREQUENTLY ASKED QUESTIONS December 13 2013 iii DENT Instruments Chapter Introduction Product Description The RoCoil TCA 5 is a three c
7. Supply Current DIMENSIONS MOUNTING Width Base Unit Assembled Height Base Unit Assembled Input Wire Connection Output Wire Connection ACCESSORIES AC DC Power Supply 50 watts Mounting Rail 0 655 mV RMS 0 5 5000 amps 80 dB Signal Range 0 5 00 amps RMS 500 1K 2 5K 5K Amps User selectable 1 25 VA per channel 50 m ohms 3 3 phase or single phase 50 60 Hz Select 1 lt 60 dB 60 deg C 140 deg F 48 VDC 10 30 Watts 0 6 amps DC 48 VDC 15 7 cm 6 2 25 0 cm 9 8 9 0 cm 3 5 12 6 cm 5 0 18 28 AWG 12 18 AWG length dependent Low Voltage 120 240 VAC High Voltage 200 500 VAC TS35 7 DIN Rail Table 1 1 Specifications The ROCoil TCA 5 is limited to 19 amps of peak instantaneous current The 19 amp limit is reached at 6 7 amps RMS when measuring 3 phase loads but is reduced to 4 5 amps RMS when measuring three currents on the same phase NOTE Operating with an output channel over 5 amps RMS can cause the RoCoil TCA 5 to overheat and become damaged All accuracies specified at 20 C 2 C with ROCoil centered on conductor Typical accuracy with ROCoil CTs lt 1 TIP Use a true RMS DVM to measure the voltage across the output terminals of the ROCoil TCA 5 A voltage above 250 mV RMS indicates that the signal may be clipped December 13 2013 5 DENT Instruments RoCoil TCA 5 Safety Summary This general safety i
8. ably reducing the accuracy of the system l TIP Use a true RMS DVM to measure the voltage across the output terminals of the ROCoil TCA 5 A voltage above 250 mV RMS indicates that the signal may be clipped December 13 2013 11 DENT Instruments Chapter Theory of Operation Input Signal DENT RoCoil current sensors produce a signal voltage in accordance with AN po dt V L Where is the current flowing in the measurement conductor and A N 11 and L are determined by the physical construction of the R Coil DENT RoCoils are manufactured to produce 2 183 a which is more commonly expressed as 131 0 mV kA 60 Hz and 109 2 mV kA 50 Hz The ROCoil TCA 5 is factory calibrated for use with DENT RoCoils The use of other Rogowski brands will introduce a scaling error The RoCoil TCA 5 is extremely sensitive and accurately translates conductor currents between 500 mA and 5000 amps into meter currents between 500 uA and 5 0 amps The operation of the ROCoil TCA 5 is best expressed using vector notation and is illustrated as a vector diagram in Figure 3 1 next page The voltage generated by the ROCoil sensor leads the current flowing in the measurement conductor by almost 90 degrees angle exaggerated for clarity labeled 1 The positive X axis 0 degrees is the current vector of the conductor being measured December 13 2013 12 DENT Instruments R Coil TCA 5 1 RoCoil Signal 2 Gain Select 3
9. eating Is there a 24 volt version Not at this time s there a single phase version The TCA 5 can be used on single phase circuits however there is currently no 1 channel model DENT Instruments 15 December 13 2013 RoCoil TCA 5 Can the TCA 5 be used with 333mV current sensors The TCA 5 includes a 90 degree phase shifter It can only be used with 333mV sensors to report current NOT POWER had the 50Hz selector on by mistake Is my collected data any good Yes the phase angle will be reported 0 6 degrees higher than actual which is also about 0 6 low for a PF of 0 866 DENT Instruments 16 November 27 2013
10. erence to radio communications Operation of this equipment in a residential area is likely to cause harmful interference in which case the user will be required to correct the interference at user s own expense Operation is subject to the following two conditions 1 This device may not cause harmful interference and 2 this device must accept any interference received including interference that may cause undesired operation DENT Instruments 6 December 13 2013 Chapter Field Installation Service Panel Power Meter R6Coil Sensors 3 5 Amp Current Outputs ml L Voltaze Leads G ZI _ fad AC DC Power Supply IN LE ER gt e Le re PL oC OK ete QO ne Es en EiS Par Le lt m EMC Filter RG Coil Signals D gel Figure 2 1 Recommended Installation The RoCoil TCA 5 is intended to be wall mounted with the output terminal facing up The RoCoil TCA 5 generates up to 20 watts of internal heat and relies on natural convection to cool itself The unit must have access to fresh air and is not intended to be mounted inside an electrical enclosure The area immediately below and above the unit should be kept clear of air flow obstructions Three RoCoil current sensors will typically be installed inside the service panel at the feeder or around the branch circuit of interest Best practice is to separate the
11. hannel integrating transconductance amplifier that translates the electrical output signal from a flexible RoCoil current sensor to a 5 amp AC current emulating a traditional 5A secondary current sensing transformer This combination enables the flexibility and ease of installation of the RoCoil to be extended to applications having power meters or panels that cannot process a R Coil signal directly The ROCoil TCA 5 is a DIN rail or panel mounted device requiring an external 48 volt power supply available as an option The ROCoil TCA 5 has four selectable current ranges 500 1k 2 5k and 5k amps and is accurate for both 50 and 60 Hz systems The RoCoil TCA 5 has been factory calibrated for DENT R Coil current sensors with an output of 131 0 mV per thousand amps at 60 Hz NOTE The RoCoil TCA 5 has been tested for electromagnetic compatibility EMC as an assembly which includes a discrete filter between the 48 volt DC power suppl and the TCA 5 Removal of this filter may result in sourious results or saturation of the high gain internal amplifier Range Indicator a Figure 1 1 Anatomy of the 5 Amp RoCoil TCA DENT Instruments 4 December 13 2013 R Coil TCA 5 Input Measurement Voltage R Coil Current Range Output Current R Coil Sensing Ranges Maximum Burden Maximum Output Impedance Measurement Channels Frequency Accuracy Channel Cross Talk Maximum Operating Temp POWER REQUIREMENTS TCA Supply Voltage TCA
12. nformation is to be used by both operator and servicing personnel DENT Instruments Inc Conforms to UL STD 61010 1 assumes no liability for user s failure to comply with these Conforms to CAN CSA STD C22 2 No 61010 safety guidelines CAUTION Service panel voltages may contain life threatening voltages QUALIFIED PERSONNEL MUST install CTs or power leads using methods consistent with NEC and local codes i WARNING Use of this device in a manner for which it is not intended may impair its means of protection When connecting the R6Coil TCA 5 to an AC load follow these steps to prevent a shock hazard 1 If possible de energize the circuit to be monitored 2 Connect the CTs to the phases being monitored 3 Use proper safety equipment gloves mask and protective clothing as required Risk of electrical shock Life threatening voltages may be present All work should be performed by a qualified electrician using proper safety equipment Dispose of properly FCC COMPLIANCE This device has been tested and found to comply with the limits for a Class A digital device pursuant to part 15 of the FCC Rules These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment This equipment generates uses and can radiate radio frequency energy and if not installed and used in accordance with the instruction manual may cause harmful interf
13. nt Range DENT Instruments 14 December 13 2013 Chapter FAQS Frequently Asked Questions Howcanltellif the amplifier is clipping The voltage across the output terminals is above 250mV RMS Correct this by using a larger wire gauge or moving the TCA 5 closer to the meter Does output clipping damage the unit Clipping the output signal does not harm the TCA 5 as long as the output current remains less than 5 amps as in the case when the output impedance is greater than 50m ohms or the output wires are disconnected Why does the TCA 5 run so hot Each channel dissipates approximately 5 watts of heat at full power Why is the TCA 5 limited to 4 5 Amps RMS on 3 single phase loads The TCA 5 has a peak internal current of 19 amps s there any configuration that can cause the TCA 5 to fail The TCA 5 will attempt to deliver more than 5 amps if the current being measured is larger than the selected range For example placing the ROCoil current sensor around a conductor with 900 amps flowing through it The TCA 5 will deliver 9 amps of current into the output even though the 500 amp range is selected on the front panel If the output burden is low enough the TCA will deliver the requested current and burn out the channel if this condition persists Note that this scenario is limited to single phase measurements A balanced three phase system will share the current between channels preventing any one channel from overh
14. sum of the wire resistance and meter burden is 250 mV This condition is satisfied at 5 0 amps RMS with a crest factor of 1 414 for an output impedance of 50 m ohms Another way to express this limit is a burden of 1 25 VA The 50 m ohm output impedance plays a critical role in the selection of output wire size and the allowable distance between the power meter and the R Coil TCA 5 The table below has been generated assuming that the meter burden is 5 m ohms leaving 45 m ohms for the wire Note that the meter distance is half the wire length 12 1 588 14 35 14 2 525 8 9 16 4 016 5 6 17 5 064 4 4 18 6 385 3 5 20 10 15 2 4 Table 2 2 Allowable Distance TIP Twisting the output cables together to reduce the effects of electromagnetic interference shortens the physical length of the cable by approximately 20 Table 2 2 sets the practical maximum length between the meter and the RoCoil TCA 5 Extremely short cable connections with large wire should also be avoided Because the amplifier operates from a fixed DC supply voltage the power delivered by the amplifier is the same for a given current regardless of the output impedance The output impedance impacts where the heat is generated If the RoCoil TCA 5 is delivering 5 amps and the output impedance is near zero then the full 1 875 watt burden is placed on the internal MOSFETS The design can tolerate this condition but the temperature of the amplifier will increase consider
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