HT Instruments Phase and Rotation Meters

HT Instruments Phase and Rotation Meters

Phase Sequence and Motor Rotation Testers determine the phase rotation of energized circuits and the rotation of motors.

Phase Sequence and Motor Rotation Testers…A small cost to protect equipment and your reputation

Phase Sequence and Motor Rotation Testers have two primary functions. Both are necessary to ensure that a motor will rotate in a prescribed direction when energized.

Determine the rotation direction of motors, clockwise or anticlockwise/counterclockwise, before connecting line voltage. Running motors backwards/wrong direction may damage expensive machinery. In these cases, motors are tested on a bench or temporary power is run to uncoupled motors for a rotation test. This can be costly, time-consuming, and hazardous, especially with high voltage motors. Using a motor and phase rotation tester, an electrician can make the final motor connections on the first attempt.

Determine phase rotation or sequence of energized power circuits. The load side (i.e. unpowered motor) and also the supply side should be checked. The phases of the line voltage must also be properly identified so that they can be connected to the motor for the desired rotation. This is true in a new or replacement motor situation, but also when working on switchgear, such as transformers, disconnects, and breakers. Utility crews or plant personnel working on switchgear must correctly connect or the result might be many backward rotating motors at different locations when power is re-applied. This can be very dangerous, plus possibly damage equipment.

Additional uses for Phase Sequence and Motor Rotation Testers

• Identifying polarity and phase of motor windings where the terminal markings have been destroyed or where connection diagrams are lost
• Determine polarity of instrument and power transformers
• Continuity tester in checking electrical circuits

How to select a phase and motor rotation meter?

• Make sure to have the right CAT safety rating for the voltages of live circuits being tested. Potential transformers (step-down transformer) are required for measurements on systems above the common CAT IV 600 V // CAT III 1000 V limit of many phase and motor rotation testers.
• Dedicated Phasing Testers are available for utility work in the kV range. Applications include checking high voltage fuses, testing for correct phase connections, and testing for absence of high voltage on de-energized lines.
• Each varies slightly in the layout of buttons/switch, LED’s, and operation. Some have a buzzer in addition to LED. Our site has instruction manuals (ask if not posted).
  Look for a model that is easy to learn.

• Hioki has a dedicated Phase Detector with non-contact clips, reducing risk of electric shock and short circuit hazards. The clips do not have any exposed metal to contact the conductor. Clip right over 10-40 mm insulated wires. Similar to voltage detectors, it uses the principle of electrostatic induction. Non-contact phase detectors offers safe and correct phase detection based on the basic understanding that a closed circuit is formed between the conductor, detecting device and the operator with reference to the earth.