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What is the cause of the compressor if not trip to its overload?
What is the cause of a compressor if not trip to its overload
Why one phase shows 0 Amps while a delta connected 3 phase induction motor runs?
Cause 2 phase is applied to the motor and another phase is disconnected ... in this condition ur motor cannot run longer ,it will trip on over current or burn ur motor winding .
What starting device is used on single phase fractional horsepower compressor motors?
A centrifugal switch is used on the starting winding of fractional HP motors. It is used to start the motor one the start winding and at a predesignated rotational speed the switch opens to de-energize the start winding and the motor carries on running on the run winding. Another device that should be on compressor motors is an unloader valve. Sometimes it is electrical driven and other times it is mechanical. It is used to used to unload the pressure from the compression cylinders. Without this pressure being unloaded the motor has to start against the pressure in the cylinder head and the added current draw on the motor is sometimes enough to trip the overload protection of the motor.
Overload Trip Class - What does it really mean?
Quite often we here of applications in which the motor protection/overload relay 'trips' during motor starting. The remedial action taken by many when faced with this problem is to select and install a replacement overload relay, generally one that provides a higher 'Trip Class' setting, for example, Trip Class 20 in lieu of the standard Trip Class 10.Note: The appears to be a general misconception in industry that Overload Trip Class relates directly to the starting time of a machine. This is not the case.All due care must be taken when selecting a protection relay offering higher Trip Class, as this can result in under protection and subsequent failure of the motor.To select an overload relay with a more suitable trip class, you must in the first instance obtain data relating to the motor's thermal withstand capabilities. That is, you need to know how many seconds (from cold condition) the motor can the sustain Locked Rotor Current before it is compromised.This information is readily available from most leading manufacturers of motors and is generally provided in one of two formats.a) Specific values for Locked Rotor Current and maximum Locked Rotor Time (from 'cold condition' ) are given.b) A Motor Thermal Withstand Curve is provided.With this information available to you, you can refer to the tables given in IEC 60947 to identify the most appropriate Overload Trip Class. This is defined as the one that provides a trip curve as close as possible to but below the overload curve of the motor. Adopting this process will ensure nuisance tripping is minimised and that the motor is adequately protected at all times.Note: If the above processes are adopted but the trip conditions continue, there are 4 possible causes.1. The motor (and overload relay) are not given sufficient time to cool between starts.2. Assuming reduced voltage start (star/delta, auto-transformer, primary resistance, soft start etc., the motor is not delivering torque sufficient to accelerate the connected load to speed. That is the starting current and starting time under RVS conditions exceeds that permissible by the overload curve.3. A more advanced protection strategy such as motor thermal modelling may be required. Motor thermal modelling allows the user to 'match' the curves of the protection device to the connected motor. This is of particular advantage when the motors thermal withstand capabilities and the start condition (starting current and starting time) fall between two curves defined by standard overload trip classes.4. The motor is simply too small for the application.Put simply, the most appropriate protection strategy is the one that allows the motor to be fully utilised without nuisance tripping or fear of motor burn-out.
3 phase 480 volt motor that continually trips the heaters?
By the phrase "trips the heaters" I am assuming that you meant the Overloads. There are 3 possible answers: 1) The Overloads are not the correct size or are in a high ambient temperature envornment. Most manufacturers have sizing charts that take these into account. 2) The motor is bad or in the process of going bad. 3) The motor is overloaded. If you are running a 7 1/2 HP motor on a load that requires 10 HP then the motor will draw too much amperage and trip the overloads.
