Yokogawa CTW User Manual

User’s
Manual

Please read this user’s manual thoroughly to ensure correct use of the
instrument. Carefully store this manual for future reference.

Models CTW15 and CTW35

Clamp-on Current Transformers

IM 77C01W03-01E

3rd Edition: Jan. 2005

1. Cautionary Notes for Safe Use of the Products

The following symbol is indicated on the instrument and in this manual to
ensure safe use.

This symbol is indicated where the operator must refer to instruction s
in the manual in order to protect both personnel and the instrument.
This symbol on the product indicates that the operator must refer to
an explanation in the user’s manual in order to avoid the risk of injury
or death of personnel and damage to the instrument. The manual
describes how the operator should exercise special care to avoid
electric shock or other dangers that may in injury or loss of life.

The purpose of the following conventional symbol in this manual is:

NOTE

Draws attention to information essential for understanding the
operation and features.

2.

Handling Precautions and Installation Location

Cross-check the Model

Make sure the model and suffix codes shown on the data plate attached to
the transformer are the same as specified in your purchase order.

Models Names
CTW15

CTW35

Clamp-on Current Transformer (for 100 A / 1 A)
Applicable cable diameter: less than

Clamp-on Current Transformer (for 300 A / 1 A)
Applicable cable diameter: less than

Φ

24 mm

Φ

36 mm

N OTE

The CTW contains a device for suppressing hazard ous volt ages that

ay arise when the secondary line is open-circuited. m

Install the transformer referring to the following figures.

How to Install and How to Remove

How to Install
Push the B part until it clicks to lock
the A part.
How to Remove
Loosen the A part using a flat-blade
screw driver to unlock, and pull the B
part in the direction of the arrow to
release.

B

A

N OTE

● Note that these current transformers are designed for use with

general-purpose instruments and have no t yet gained any of ficial
certification. They cannot therefore be used for the purpose of
ascertaining wattage or other electric parameters.

● Use each current transformers under a load no greater than its
rated level. When calculating the load, you must calculate the
sum of the load given by the instruments to be connected to the
transformer and the load given by the lead-wire of the
secondary-stage cable.

● The inner-walls of the clamp are treated with rust prev entiv e. But
if rusted, remove the rust with CRC-5-56 (goods on the market)
and spray rust preventive on the inner-walls again for recovery.

Avoid installing the current transformers in locations subject to:
ambient temperatures outside the specified range of -20 °C to 50 °C, where
condensation is likely; ambient humidity exceeding 80 % RH, where
condensation is likely; relatively large amounts of flammable or explosive
gas, saline substance, lampblack or dust; splashes of water, oil or solvent;
radioactive rays or intense electric or magnetic fields; frequent mechanical
vibration or shock; or direct sunlight.

3. Installation

W ARNING

Since there is a risk of electric shock during installation, be sure to
observe the following.

● Before connecting the transformer to any other equ ipment, make
sure the circuit is not receiving any power in order to prevent
electric shock.

● Fasten the connecting terminals securely so they will not loosen
readily.

● Do not touch the terminals or any other part of the transformer
when the circuit is live.

● Do not use the transformer under a circuit current greater than
the level specified for that model.

● Do not use the transformer under a circuit voltage greater than
500 V AC.

Example of Installation

Power-source side

K

Cable

Banding band

Secondary­stage cable

l side=black
k side=white

Load side

L

● Attach the transformer to the cable according to the orientation of the
K and L symbols, as shown in the figure.

● Be careful not to make a gap between the inner-walls of the clamp.

● Be careful not to trap any dust between the inner-walls of the clamp.

● Use a crimp-on terminal for 0.75 mm
secondary-stage cable.

● The wires of the secondary-stage cable are color-coded as follows.
k side=white; l side=black

● Fix the transformer with a banding band or the like as shown in the
figure above to prevent it from falling.

2

cables to connect the

1

IM 77C01W03-01E 3rd Edition : 2005.01.15-00

NOTE

When extending secondary-stage cable of the current transformer,
use a covered ring-sleeve or the like and a cable of 1.25 to 2 mm².
The standard cable length is as follows.
Up to 8.3 m for 1.25 mm², and up to 15 m for 2 mm²

4. Disposal

These current transformers, when no longer serviceable, must be disposed
of as industrial refuse.

5. Specifications

5.1 General

The CTW series are clamp-on current transformers that can be installed
much easier than conventional current transformers, w hereby sav ing labor.
These transformers are particularly useful w hen exp anding ex isting system
since you can attach them to a cable without having to cut it.

5.2 Characteristic Specifications

Rated primary current (In) / Rated secondary current:

CTW15= 100A / 1A

CTW35= 300A / 1A
Rated frequency: 50 / 60 Hz
Rated burden: 0.5 VA
Accuracy / Linearity: ±1.0% against rated primary current In
Phase difference: Within ±2° against rated primary current In
Operating circuit voltage: Within 500 V AC
Insulation resistance: 100 MΩ or more at 500 V DC (across core and

Withstand voltage: 2000 V AC for one minute (across core and output)
Operating temperature range: -20 to 50°C (no condensation)
Operating conditions: Indoor location
Weight:

CTW15= Approx. 160 g

CTW35= Approx. 220 g

output)

6. External Dimensions

6.1 CTW15

451.5

k(White) l(Black)

AWG18

6.2 CTW35

571.5

6

3

φ

(2.5)

4

2

φ

36

+20

+ 0

(2.5)

Unit: mm

3444
22

K

64

39

- 0

190

- 5

10

K

L

3844
22

L

80

49

45

k (White)

AWG18

l (Black)

+20

- 0

190

+ 0

- 5

10

IM 77C01W03-01E 3rd Edition: 2005.01.15-00

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