Megger Transformer Winding Resistance/Tap-Changer Ohmmeter Specifications

Specifications

Measuring Principle

Environmental

Electronic Thompson-type circuit

Operating:

32 to 104° F (0 to 40° C), relative humidity to

Input

80%.

120/240 V, 50/60 Hz, 350 VA

Storage:

-40 to +150° F (-40 to +65° C)

Output

Temperature Coefficients:

Current Ranges:

±0.05% of applicable accuracy

5 mA, 50 mA,500 mA, 5 A (dc)

specifications per degree Celsius of resistance

Open-Circuit Test Voltage:

range.

30 Vdc

Rating:

Displays

Continuous use on all ranges

Two high-temperature, 0.7 in. (18 mm), liquid-

Resistance Measurement Inputs

crystal, 31/2-digit displays showing 1999 at full

Two isolated high-impedance inputs, each with

scale. Update rate is approximately three times

separate range control and protection provided

per second.

for flashover caused by inductive kickback.

Ranges

Dimensions

Accuracy: ±0.5% reading, ±0.5% full scale

Instrument

(when current has stabilized).

11" (H) x 16" (W) x 10.5" (D)

Overrange:

280mm (H) x 406mm (W) x 267mm (D)

Lead number one displayed with all other digits

Transport Case

blanked.

13" (H) x 20" (W) x 21" (D)

330mm (H) x 508mm (W) x 533mm (D)

Nominal (ohms)	Resolution (ohms)	Maximum Display (ohms)
2m	0.001m	1.999m
20m 200m	0.01m 0.1m	19.99m 199.9m
2 20	0.001 0.01	1.999 19.99
200	0.1	199.9
2000	1.0	1999

Weight

Instrument:

Net 40 lb (18 kg)

Shipping:

66 lb (30 kg)

Features and Benefits

Direct digital reading saves time, no balancing is required.
Built-in discharge circuit safely discharges the specimen when test is completed, if lead accidentally disconnects or if power is lost.
Electromechanical safety indicator gives a visual indication of a charged or discharged specimen, even if
power to the instrument is lost.
Two independent measuring channels allow simultaneous testing of primary and secondary windings
or measurement of two phases at a time.
The sensitive surge detection circuitry monitors the contact operation of on-load tap-changers for the proper make-before-break sequence. If an open circuit condition exists, the instrument shuts down immediately.
High-accuracy, four-terminal bridge: no lead compensation required.
Electronically generated and regulated current supply overcomes high-inductance transformers quickly,
allowing fast measurements to be taken. Display of measurement occurs only after test current stabilizes.
Wide resistance range allows heat-run testing of many transformer types.
Lightweight and portable, the Transformer Ohmmeter is ideal for use in shop or substation environments.
Over-temperature protection provides automatic current shutdown and LED indication to prevent instrument damage.
Instrument and accessories come in a foam-lined transport case.