KCTS Current Transformer Testing System


The Knopp Current Transformer Testing System (Type KCTS) is designed to measure the accuracy of instrument transformers having 5 ampere secondaries and primaries up to 8,000 amperes. When purchased with the optional Type KATC-C1 Comparator, the KCTS is capable of testing transformers with 1 or 5 ampere secondaries. The system uses a high accuracy multi-range current transformer as a reference standard. All ANSI standard burdens are included. The phase angle and ratio errors of the transformer-under-test are measured by the built-in Knopp Automatic Transformer Comparator.


A. General

  1. The test system shall be able to check the accuracy of instrument transformers having primary ranges from 5 to 8,000 amperes.
  2. The test system shall include a built-in, microprocessor-controlled, automatic, auto-ranging comparator.
  3. The test system shall utilize a motor-driven Variac to reduce test time.
  4. The test system shall incorporate protective circuitry to ensure the safety of the operator, the test system, and the transformer-under-test.
  5. The accuracy or calibration of the precision transformer must be traceable to the National Institute of Standards and Technology.
  6. The test system shall be suitable for 60 Hz. operation.

B. Test Ranges

  1. The following primary ranges shall be provided: 5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 80, 100, 120, 125, 150, 160, 200, 250, 300, 400, 500, 600, 750, 800, 1000, 1200, 1500, 1800, 2000, 2500, 3000, 4000, 5000, 6000, 7500, and 8000 amperes.
  2. 400% tests shall be able to be performed on all ranges up to, and including, 2000 amperes.
  3. 200% tests shall be able to be performed on all ranges up to, and including, 4000 amperes.
  4. The secondary current shall be 5 amperes.

C. Test Burdens

  1. The following ANSI burdens shall be switch selectable: B-0.1, B-0.2, B-0.5, B-0.9, B-1, B-1.8, B-2, B-4, and B-8.
  2. These burdens shall be of a passive design and shall be very stable and highly accurate (the resistive and inductive component values shall be accurate to within 1%).
  3. Burdens up to, and including, B-1.8 shall be rated for 400% testing, while the remaining burdens (B-2, B-4, and B-8) are rated for 200% testing.
  4. Provisions shall be made for connection of an external burden.

D. Comparator

  1. The comparator shall be dedicated to the test system. It shall only be capable of testing current transformers.
  2. The comparator shall be automatic and autoranging to provide minimum measurement time. Measurements shall be completed within 5 seconds of adjusting the test current.
  3. The comparator shall digitally display test current and test results. Test results shall consist of ratio error (in % or RCF) and phase error (in minutes or milliradians).
  4. The comparator shall calculate and digitally display the best accuracy class for which the transformer-under-test qualifies.
  5. The comparator shall include protective circuitry which senses error conditions such as wrong ratio or wrong polarity and then automatically removes power from the test system loading circuitry.
  6. The comparator shall offer RS-232 test result output options.

E. System Accuracy

  1. The combined error of the precision current transformer and the transformer comparator shall be no greater than 0.025% on ratio and 2 minutes on phase angle at 100% full load current.

F. Self Check

  1. The calibration of the precision transformer shall be able to be periodically checked by the One-to-One method, whereby the ratio and phase angle performance can be quickly and accurately checked without the use of an external reference standard.

G. Input Power Requirements

  1. The test system shall operate off of 240 VAC or 208 VAC (to be specified at time of order), single-phase service at a maximum 200 amperes.
  2. A separate 120 VAC, single phase, source at a nominal 5 amperes is required.


H. Weight and Dimensions

  1. The approximate weight of the test system shall be 1500 lbs. (680 kg).
  2. The test system shall measure approximately 39 in. (99 cm) High, 55.5 in. (141 cm) Wide, and 35 in. (89 cm) Deep.

I. Instruction Manual

  1. An instruction manual and schematic diagrams shall be furnished with the test system.

J. Options

  1. A cable and hardware kit for connecting the transformer-under-test to the test system shall be able to be purchased separately.
  2. A demagnetizing feature shall be available as an option.
  3. 50/60 Hz. operation shall be able to be specified as an option.

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