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How to test a forward and reverse motor circuit

#How to test a forward and reverse motor circuit install

So we connected it to a CTR-101 curve tracer to run the forward characteristic curve.

The forming current is a minimum current to regenerate the proper operation. The Wikipedia page on Selenium Rectifier mentions that a ‘forming current’ may be required after a long period of disuse, and long period of disuse applies in this case: it had been out of service 40 years or more. Was the selenium rectifier still good? We measured the forward and reverse resistance with a multimeter, and the results were inconclusive. The owner of the bike had replaced the selenium rectifier with a modern three-phase silicon diode array, a much smaller and probably more efficient device. The rectifier consists of three diodes with one common terminal, so that the output is a reasonable approximation of direct current. The alternator is wired to produce 3 sine wave outputs, each 120 degrees apart. We were given a three-phase selenium rectifier, taken from an ancient Honda 150 motorcycle. Selenium rectifiers are recognizable by the cooling fins, which are often painted green or orange. The selenium rectifier replaced the vacuum tube rectifier in the period 1950 onward and was in use until the 70’s. If the sequence is reversed, then the relay de-energize the circuit.Before the invention of the silicon diode, designers had the choice of germanium point contact diodes for low currents, copper-oxide rectifiers in instruments, and selenium rectifiers for power applications.

#How to test a forward and reverse motor circuit install

Only the direction or phase sequence finalized, then we have to install the phase reversal relay. By that we should find out the correct direction of the motor. To install these relay, first we should run the motor without relay. Solid state relay sense the phase sequence of the motor. Hence the disc contact open the circuit and motor will be isolated.

If the direction of the motor is reversed, then simultaneously the direction of the disc also reversed. Under normal condition, the disc does not open the auxiliary contact and the motor starts rotating. The auxiliary contact for particular direction from the disc is given to the motor starting circuit. The disc rotates parallel with the motor. In old days, before microprocessor relays, this protection is provided using motor driven disc working on electromagnetic principle. Learn More: Summation Current Transformer Calculations Mechanical phase reverse protection: VFD has option to change the output voltage to the motor

Drive with VFD we can changes the direction of the motor.

In home island generator, upon changing the phase sequence of the generator, the connected all motor’s phase sequence also changes.

See the reverse sequence will be R-U, Y-W, and B-V. But you should not do in both the places. It can be done either in motor terminal or input three phase terminal. The direction of the motor can be revised by changing the phase sequence of the motor. However, the direction of the motor is purely depending on the direction of rotating magnetic field. In motor terminals are powered by R-U, Y-V, and B-W always gives clockwise direction (Note: It may be reversed). These directions can be controlled doing phase reversal of the motor. The direction of induction motor depends on the direction of rotating magnetic field produced by the stator windings. Learn More: What is Ethernet, Basic, Cabling, Types of Data Transfer Phase Reversal Protection working Principle: Phase reversal protection generally do the job perfectly. So that we need high speed tripping when the phase sequence of the motor changed. But it takes few seconds to operate the tripping circuit. However, Motor over current protection will trip the motor. But the wrong direction, the output of the pump will be affected. But some of the application does not affect the motor example: pumps. These high current damages the motor winding or increase temperature etc. That arrangement blocks the motor rotation if its reverse, due to that the motor take high current (Motor goes to locked rotor condition). i.e The belt conveyor motor mechanical gears are having mechanical reverse direction protection arrangement. But Running a induction motor in reverse direction with mechanical loads causes heavy l oad current flow on the motor’s stator winding and severe damages on the mechanical side when the direction should not have reversed.Įxample cranes, hoists, lifts or in threading mills, belt conveyors. Normally running a motor in reverse direction does not affect the system when the motor is empty (without mechanical coupling).

Phase reversal protection is used to protect the induction motor, from running in reverse direction. Phase Reversal Protection | Induction Motor Protection: