Table of Contents
What is a stator core loop test?
The loop test is a procedure for energizing the stator core with an external source of magnetic flux densities to simulate operating conditions. The test models a transformer turn ratio on a single phase – single coil basis for convenience.
What is a core loss test?
A core loss test is the only method of determining how a motor’s core is behaving, what temperatures it is reaching and how it has been improved after repair procedures such as a rewind. Results are logged as part of the overall quality process, and instantly and automatically compared to the component’s history.
What test is performed to find out the core losses of an induction motor?
The no load test and the blocked rotor test are two main induction motor tests, which are performed on induction motor to know the different losses, power factor and efficiency of the induction motor.
What is core loss in motor?
“Core Loss is a Waster of Energy and Destroyer of Motors” Not all power applied to an electric motor is converted to work. Principal sources of energy waste include winding loss (I²R), windage, friction, stray load loss and loss in stator, rotor and armature cores.
What is core loss of stator?
The losses in the stator and rotor iron cores are due to the space fundamental and harmonic fluxes. These losses consist of hysteresis loss, eddy current loss, and excess loss. Hysteresis and eddy current losses are proportional to frequency and square of frequency, respectively.
Why power factor is low at no load?
At no load, an induction motor draws a large magnetizing current and a small active component to meet the no-load losses. Therefore, the induction motor takes a high no-load current lagging the applied voltage by a large angle. Hence the power factor of an induction motor on no load is low.
How do you test a motor with no load?
The no-load test of an induction motor is similar to the open-circuit test of a transformer. The motor is not connected from its load, and the rated voltage at the rated frequency is applied to the stator to run the motor without a load. The 2-wattmeter method measures the input power of the system.
What are the two 2 main types of losses in a motor?
There are two main kinds of losses in electric motors, which are often referred to as iron losses and copper losses. Dealing first with iron losses, these are made up of two ‘components’, namely eddy current losses and hysteresis losses.
How does core loss occur?
The term core loss relates to the total energy lost through the generation of heat. Core loss is the loss that occurs in a magnetic core due to alternating magnetization, which is the sum of the hysteresis loss and the eddy current loss.
How do you calculate core loss?
Core loss is generated by the changing magnetic flux field within a material, since no magnetic materials exhibit perfectly efficient magnetic response. Core loss density (PL) is a function of half of the AC flux swing (½ B=Bpk) and frequency (f).
How do you calculate stator loss?
Example With Calculations
- The synchronous speed of the motor = (50 ×120) / 6 = 6000 / 6 = 1000 rpm.
- Slip = (Synchronous speed – Actual speed) = 1000 – 960 = 40 rpm.
- Percentage slip = [(40 / 1000) × 100] = 4% = 0.04.
What are the signs of a low power factor?
A low p.f. means a higher load current than necessary and accompanying higher line losses. Inductive loads are the main cause of a low p.f., with induction motors the major contributors.
What happens when power factor high?
A high power factor reduces the load on transformers and distribution equipment. A high power factor decreases the I2R losses in transformers, distribution cable, and other equipment, resulting in a direct saving of kilowatt-hour power consumption. A high power factor helps stabilize the system voltage.
When motor runs on no load then?
When the motor is connected across the supply mains without load, it draws small current from the supply mains. This current will flow through the series field and armature, the speed tends to increase so that back emf may approach the applied voltage in magnitude.
What happens if motor runs without load?
In case of electric motors, running on no load does not have any effect on the motor, other than a little bit of wear. It is no problem at all for the motor. For a combustion engine, no load might be a bigger problem.
What is a loop test on a generator?
The Loop test involves exciting or fluxing the stator core to, or near to, the full rated flux of the generator by means of several turns of a high voltage insulated winding through the bore and around the outside of the stator. This induced flux produces fault currents similar to when the generator is in operation.
What is a generator stator made up of?
A key component of the generator is the stator. The stator is made up essentially of windings and an iron core. An iron core can develop core losses because of winding failure, aging and deterioration due to heat. Iron cores are made of thin laminated steel sheets.
What is the best way to test stators?
Two extremely useful testing technologies used for quality control of stator repairs are Loop tests (Ring Flux tests) with Thermography and Electromagnetic Core Imperfection Detector or ELCID. Both have their advantages and also their limitations and thus compliment each other perfectly.
What is core flux loop test?
Core flux “Loop” test is the standard test utilized for evaluating the insulation integrity of laminated stator cores. The test establishes a specific magnetizing level for the core by energizing the loop coil with single phase power.