h��VYo�6�+|LPH��CE`���hv�q�5��ȌW]Y2d�X���P��h��E03�pF3��#ͥ%�p��@�$'�� QZ���h2"ƢT�*�`c �J�NK������O1"$:����� B�=�d��~��[�@#9������ �ۮ�uV8?�\��)u�K�*K�. Winding Resistance. 3. Motor resistance Ra (ohms) Motor inductance La (Henries) Motor inertia Jm (lb-in-sec^2) Load inertia reflected to the motor armature shaft Jload (lb-in-sec^2) Total inertia=Jm+Jload Jtotal(lb-in-sec^2) Note that the above values are stated for a single winding with dc motors, and are the phase values for a BLDC motor. 23 0 obj <> endobj 21 0 obj <>stream - Winding DC Resistance Test - Follow USACE procedure - Three sets of results total (A to B phase, B to C phase, C to A phase) - Correct values to 40°C using the formula in step 8. Testing For Open & Short In Motor Winding. Place the meter lead on the winding that has the lowest reading. The winding temperature should be 25°C ± 15°C. Here I assume a two pole distribution because it makes the explanation eas-ier. Resistance between two winding and winding - frame should be more than 1,5 Mohm. The algorithm is intended to capture slow variations of stator resistance which are given by the changes in stator windings temperature. Winding resistance, the resistance of a length of copper wires or bars from one end to the other, is a measure of DC voltage and current and the application of Ohm’s law as follows:. The reading of the motor winding machine can be displayed on the multimeter screen that is resistance in ohms. 137 0 obj <>/Filter/FlateDecode/ID[<9D9EBC62EF019E42A82C33BDF3C2C770><9D9EBC62EF019E42A82C33BDF3C2C770>]/Index[113 70]/Info 112 0 R/Length 120/Prev 540273/Root 114 0 R/Size 183/Type/XRef/W[1 3 1]>>stream Here’s a real world example. 3 shows a typical scale, which reads increasing resistance values from left up to infinity, or a resistance too high to be measured. ` ?j� When a permanent magnet DC (PMDC) motor fails to operate properly, or fails to run at all, one sensible troubleshooting step is to measure the winding resistance to determine if there’s an open circuit or a short circuit, either between turns of the same winding, between two windings in the same motor, or between a winding and ground. It depends on the size of the motor. The specific resistance depends on winding wire size. where R is resistance in Ohms, V is voltage applied in Volts and I is the resulting current in Amperes. (Four and six pole motors run at 1720 to Capacitor Start Motor. h�bbd```b``.�% ���d]"����0��f� f���"�`v?�9"��@� 182 0 obj <>stream Resistances of three winding should be same (+/- 5%). Winding resistance of three-phase AC motors is measured between their terminals (all three combinations). Three-phase motors: measure the resistance line-to-line for all three combinations. (See 4 and 6 pole distri-butions on the handout from class.) The Winding Arrangement section also displays the following values (in electrical degrees): Transient FEA Input Data This information is used when calculating the motor performance using the 2D time transient finite ele-ment field solver. winding check with ohmmeter1.pdf - Free download as PDF File (.pdf), Text File (.txt) or read online for free. Steady state operation with harmonic voltages and currents are located during the operation of the motor and the stator resistance is determined from RMS values of IR Value for Electric motor For electric motor, we used a insulation tester to measure the resistance of motor winding with earthing (E). ings overlap and each winding slot has two windings in it usually from different phases. Place meter on ohms: T1 to T2 T2 to T3 T1 to T3 The scope generally expected is.3 to 2.0 ohms, although most are all about .8ohms. 2008-10-20T14:19:06-04:00 endstream endobj 114 0 obj <> endobj 115 0 obj <> endobj 116 0 obj <>stream scale. The minimum test value of motor insulation resistance is 1 meg ohm (1 mH). Insulation resistance varies very little with rating. h�b```f``��������A���2,@�1��������]���^,��mXe�k�9�L]�p����m�zM־�}hrA�>t��b BL � �L J� �� �x�Gr�(30�dd�j�u@��� ,9Lz���* R6p,hq_#)T������J���G����*��8��A�Lr@ڔ����gd0 �\C� Measure resistance for each winding, resistance between two different winding and resistance between winding and motors frame. You can detect burned motors winding by unique smell (smells like burned lacquer). Minimum insulation resistance of the winding to ground is measured with 500 V DC. Maximum insulation resistance should be measured with 500 V DC with the windings at a operating temperature of 80 – 120°C depending on the motor type and efficiency. 0 Checking This data is restated below: Condition of Motor & Leads Ohm Value Megohm Value Motor out of wet well (without cap/cable attached) A new motor 20,000,000 or more > 20.0 A used motor which can be reinstalled in wet well 10,000,000 or more > 10.0 Curve A shows test values as measured; Curve B shows same values corrected to 20°C (see page 22), giving a definite downward Remember that the three phases have identical windings or nearly so! In accordance with IEEE 43, clause 9.3, the following formula should be applied. The start capacitor is only connected when starting the motor and its disconnected automatically by a centrifugal switch when the motor is up to speed. Set the voltage level of the insulation resistance tester to 500V. 2-wire vs 4-wire measurement Check the motor frame (earth) from phase to phase (U to E, V to E, W to E). At B, the sharp drop indicates an insulation failure. At C, the insulation resistance value after the motor has been rewound. Usually, if it’s open, it is infinite or well above 2K ohms. A 24 volt motor will be low, 4160 will be quite high. Something on the order of 0.01 ohms or so. Example of the variation of insulation resistance over a period of years: At A, the effect of aging and dust accumulation is shown by decreasing values. Acrobat Distiller 5.0.5 (Windows) Figure 4–Typical record of insulation resistance of a mill motor. If all ohms values are normal (Tables 13, 22, 24, 25, & 27), the motor windings are neither shorted nor open, and the cable colors are correct 2. Such a motor runs at the nominal speed range of 3500 – 3580 RPM. Motor voltage also plays a part. H��W�n7�߯�yȺ� �d�Er�M. Part Number Description Quantity; BP5125A01SP: CARBON BRUSH - SERRATED H45 - FOR 36D: 1.000 EA: BP2000A01SP: BRUSH SPRING FOR DC MOTORS: 1.000 EA: 36CB3000SP 4.1 Present motor versions (C, E &A) Single-phase: motor code C Star-Delta (Y/Δ): motor code E Part Winding 2/3:1/3: motor code A The test current should not exceed 10% of the nominal winding current. Place meter on ohms and generally the range can be expected from 3 to 2 ohms. The winding resistance measured at the motor should fall within the values in Tables 13, 22, 24, 25, & 27. U, V, W is a European winding designation. If you open the single phase motor , you will find out that your motor have two types of winding in which one is made from thick wire gauge and one thin. 2.4 WINDING RESISTANCE TEST A typical 3-phase squirrel-cage motor has six connection leads in the electrical connection box for the three coils. If someone works with AC 3-phase motors, then it is important to know how to connect these motors in Star and Delta connection, and how to detect an electrical problem. For rated voltage below 1KV, measured with a 500VDC Megger. application/pdf %PDF-1.6 %���� AC Motor Winding Resistance Test Check the motor winding resistance or ohms reading using a multimeter or ohmmeter for phase to phase terminal ( U to V,V to W ,W to U ).The ohms reading for each winding must be the same (or nearly the same). %PDF-1.4 %���� uuid:3ecabba6-19f5-4319-999e-08b10e232ec4 Values greater than this indicate a potential problem and values significantly greater than this indicate the winding has failed opened. Small motors with fine wire might have 50 - 100 ohms, a 50 hp motor might have 2 - 3 ohms. Take each resistance reading after 60 sec. - Record initial and corrected values on Motor Testing Record sheet. On 2-wire motors: measure the resistance from line-to-line. reference data such as a guide to Insulation Resistance Readings. 2005-06-06T22:23:57Z 2008-10-20T14:19:06-04:00 uuid:f91e1a75-4ab9-4e78-aea7-f694061f3e38 When measured through the drop cable, the resistance of the drop cable must be subtracted from the ohmmeter readings to get the winding resistance of the motor. %%EOF 4 Internal connection of the motors If the motor winding resistance needs to be measured the diagrams below show the internal connections for the motors used on Copeland™ semi-hermetic compressors. endstream endobj startxref If you read zero, a brief between phases exists. connect to measure the resistance of each winding lead to ground. Record the lowest reading. 4 3 2 1 TO GROUND DISCHARGE THE MOTOR WINDINGS T1 T2 T3 INCREASE METER SETTING BY 500 V; RECORD READING ON GRAPH AFTER 60 SECONDS LOWEST READING ON WINDING WITH See table below. endstream endobj 19 0 obj <> endobj 24 0 obj <> endobj 1 0 obj <> endobj 4 0 obj <> endobj 7 0 obj <> endobj 10 0 obj <> endobj 13 0 obj <> endobj 16 0 obj <> endobj 18 0 obj <>stream 1. Winding check....for motor connections Because of cables heating, higher values of test current will significantly increase the winding resistance. Fig. Winding resistance measurement – How Decide if single or 2-ch measurement/current injection is appropriate Connect current and voltage measurement cables to the actual transformer winding(-s) Select test current Start test Wait for measurement results to stabilize When stable value, stop measurement/store result, discharging starts automatically - All values obtained from Winding DC Resistance Test should be below 1 Megohm and similar in value A motor with high resistance will not run - or not run with speed control (as is the case when a 3-phase motor winding opens while running). MEASURING MOTOR PARAMETERS A small one horse three phase 460 volt motor may have several ohms of winding resistance. For rated voltage above 1KV, measured with a 1000VDC Megger. X\�X|'�| $���ص�$��$ ��*�� �*�{iE�|���T!�30�{ require additional external excitation. 2. Motors of all hp, voltage, and phase rating have similar values of insulation resistance. 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