305C Series Vishay Cera-Mite PTCR Motor Start Packages PSC Single Phase Motor Start Assist • ECONOMICAL SOLID STATE TORQUE ASSIST FOR HEAT PUMPS, ROOM AIR, COMMERCIAL AND RESIDENTIAL AIR CONDITIONING AND REFRIGERATION SYSTEMS Safety Agency Recognition Vishay Cera-Mite motor start PTCRs are recognized by Underwriter Laboratories file E97640 in accordance with Standard for Thermistor Type Devices UL 1434; and Canadian Standards C22.2 No. 0-1991. Positive Temperature Coefficient Resistors have been used for many years in millions of HVAC applications to provide starting torque assistance to Permanent Split Capacitor (PSC) single phase compressor motors. Sizes are available to cover the full range of 120/240 volt PSC compressor motors. RELATIVE COMPARISON OF VARIOUS MOTOR STARTING METHODS Three methods have historically been employed to generate starting torque for PSC motors. All are well-proven technologies and may be compared relative to one another based upon categories shown below. The importance of each category is dependent upon the motor application and industry sector. In general, if the PTCR starter produces sufficient starting torque, it is considered the simplest and most economical choice. Table 1 MECHANICAL STARTING METHOD PTCR Starter Start Cap with PTCR Acting as A Current Relay Start Cap used With Potential or Current Relay EASE OF WIRING Simple 2 Wire Moderate 2 or 3 Wire Difficult 4 or 5 Wire ELECTRICAL FINANCIAL PANEL SENSITIVE TO ACCELERATION ACCELERATION RESET INVENTORY SPACE MOUNTING TORQUE (SWITCH) TIME EMI/RFI MIX PURCHASED REQUIRED DIRECTION PRODUCED TIME REQUIRED GENERATED TECHNOLOGY REQUIRED RELIABILITY COST Lowest No Lowest Fixed 3-5 No Solid State Lowest Highest Lowest Minutes Medium Yes Medium Fixed 2-5 No Solid State Medium Medium Medium Minutes Highest Yes Highest Variable Based on Motor Speed None Yes Electro Mechanical Highest Lowest Highest SIMPLIFIED PTCR STARTING DIAGRAM Fig T-2 L1 Restart. It is important to provide time between motor starts to allow the PTCR to cool to near its initial temperature. This time is usually 3 to 5 minutes and is determined by the thermostat (THERM) or separate time-delay relay (TR). Attempts to restart in less time may be successful depending on compressor equalization, line voltage, temperature, and other conditions. If the motor were to stall in a locked-rotor state, overload device (PD or TS) would open the line and a further time delay would occur until the motor overload is reset. Motor start PTCRs are applied to compressors having means to equalize pressure during shutdown. TYPICAL PTCR CHARACTERISTICS AS A MOTOR START DEVICE Fig T-3 10,000 PTCR Resistance (ohms) Start Sequence. When starting the compressor, contactor (M) closes; the PTCR, which is at low resistance, provides starting current to the motor’s auxiliary winding. After time delay (t), the current passing through the PTCR causes it to heat and “switch” to a very high resistance. At this point the motor is up to speed and the run capacitor (C R ) determines the current in the auxiliary winding. The PTCR remains hot and at high resistance as long as voltage remains on the circuit. When contactor (M) opens, shutting off voltage to the compressor, the PTCR cools to its initial low resistance and is again ready to provide torque assist on the next startup. CURRENT 20.0 PTCR Current (Amperes) 1,000 100 Switch Time (t) RESISTANCE 10 0.02 150 50 100 PTCR Temperature °C 20.0 PD M Protective Device THERM TR M AC Line 120 or 240 VOLTS AC M Protective Device PSC MOTOR TS Internal Motor Winding Overtemp. Switch Optional OFF Time Delay TR Relay M MAIN CR AUX. PTCR L2 Low Voltage Control Transformers Not Shown Document Number: 23086 Revision 14-May-02 [email protected] www.vishay.com 3 305C Series Vishay Cera-Mite PTCR Motor Start Packages START AND ACCELERATION TORQUES SINGLE PHASE PSC HIGH EFFICIENCY COMPRESSORS The use of a PTCR start assist insures sufficient acceleration torque to overcome not only breakaway friction, but also parasitic asynchronous torques associated with the 5th and 7th motor harmonics or lamination slot harmonics. Fig T-4 100 A1 ACCELERATION TIME CONSIDERATIONS RPM x WK2 (lb ft 2 ) Avg. Torque (lb ft) x 308 (Avg. Torque = Curve B - Curve A) 1. If (Curve B - Curve A) is zero or less, the motor may stall. 2. In calculating torque available from Curve B, allowance should be made for cusps in the torque curve due to harmonics. The time needed to accelerate from rest to 1/2 speed is critical, as the average torque available in this region is limited. Select a PTCR with sufficient switching time (t) to accelerate the compressor. Percent Rated Speed The time to accelerate a rotating machine is: Accelerating Time (Seconds) = Full Load Operating Point A2 max. Torque 75 50 B1 25 B2 5th Possible Region of Harmonic Torques 7th Slot 0 100 CURVE A1 Torque req’d to accelerate unloaded compressor 3. Scroll and rotary compressors may have less breakaway torque than shown. 4. A compressor with no equalization may require over 100% starting torqe and time as long as several seconds. PTCR starters not recommended. 200 Percent Rated Torque Cold Breakaway Torque CURVE A2 Torque req’d to accelerate compressor at partial differential pressure CURVE B1 Motor speed versus torque with run cap only CURVE B2 Motor speed versus torque with run cap and PTCR CONSIDERATIONS FOR CURRENT IN PTCR APPROXIMATE EQUIVALENT CIRCUIT PSC MOTOR AT ZERO SPEED Fig T-5 HP x 746 IL (run) = Line Voltage VM IL (start) ≈ 6 x IL run L2 L1 VM x pf x eff IL IL If Vaux = VM, then IM and Iaux = If Vaux ≠ VM, then Iaux = RM * IM XM * Iaux For running conditions: IL √2 VM x √2 Ic C VM and Zaux = Vaux Iaux Xaux Raux PTCR Vaux IR *R and X are total of stator and rotor For the greatest starting torque, PTCR should be chosen to make: VM x IM = Vaux x Iaux. In many cases the auxiliary VoltAmperes are limited to about 50% of the main winding Volt-Amperes to get 50% - 70% rated torque. Fig T-6 Simplified Voltage Diagram of the PSC Motor at Operating Speed Then at start, with PTCR in series: Z'aux = R PTCR + Zaux VM I R start through PTCR = Z'aux *IA (auxiliary current) leads IM (main current) by 80° to 90° when C (run capacitor) is chosen for balanced operation at 3/4 to full load. Line Power Factor = sine 2θ IC start through Run Cap = θ 1 VM ; Xc = ohms Xc 2 πf C ∗ Iaux start = IR start + IC start If Zaux is low impedance, less than 10% of RPTCR then it can be ignored and IPTCR at start = V M RPTCR This closely approximates the condition for motors over 1/2 HP. www.vishay.com 4 [email protected] VM Applied Voltage V CR PT =V C =I C A θ IA IM ∗ VA Document Number: 23086 Revision 14-May-02 305C Series PTCR Motor Start Packages Vishay Cera-Mite EFFECT OF PTC RESISTANCE ON STARTING TORQUE OF PSC MOTORS Table 2 A. Rated torque is the torque at full speed rated load. It is calculated as: HP x 5250 Torque (lb - ft) = RPM LOCKED ROTOR STARTING TORQUE WITH RUN CAP TORQUE WITH RUN AND PTCR (% RATED TORQUE) (SEE B) MOTOR HP CAP ONLY RESISTANCE (Rdyn) (TABLE 4) % RATED TORQUE (NOTE 7) (SEE A) 50 ohm 25 ohm 20 ohm 12.5 ohm 10 ohm 0.5 25% to 35% 70 - 100% 80 - 100% NA NA NA 1 25% to 35% 50 - 70% 70 - 100% NA NA NA 40 - 60% 60 - 90% 70 - 100% 70 - 100% 80 - 100% 2 20% to 30% 3.5 20% to 30% NA 5 15% to 25% NA NA 6.5 15% to 25% NA NA The range shown includes both normal slip and high efficiency low slip motors. Starting torque varies as: (Line Voltage) 2 . B. Figure T-4 shows effect of using PTCR to increase starting torque. For reciprocating compressors, it is advised to choose a resistance value that gives at least 50% rated torque at locked rotor. Scroll and rotary compressors may require less torque. 40 - 60% 50 - 85% 60 - 90% 70 - 100% 40 - 60% 50 - 75% 60 - 90% NA 40 - 70% 50 - 80% TYPICAL PTCR CURRENT VS. TIME SHOWING DEFINITION OF RDYN AND SWITCH TIME (T) Fig T-7 Time (t) ≈ KM (130°C - T0) Peak Current OSCILLOSCOPE I PTCR Amperes (RMS) (Normalized) Applied Voltage (ERMS) 20% Peak Current IPTCR ERMS I PTCR at .05 Sec V 2 PTCR M = PTCR mass T0 = PTCR temp at time 0 K = 0.75 J/g/ °C SHUNT R DYN = RDYN PTCR Switch Time (t) 0 0.1 0.2 Motor Contactor Closes 0.3 0.4 0.5 0.6 0.7 Time to Switch (Seconds) START CAPACITOR REPLACEMENT STARTING CURRENT APPROXIMATION BASED ON Capacitor Starting Comparison Some PSC motors have historically been started with a capacitor and relay. To deliver the same starting current as a start capacitor, a PTCR resistance is available for approximately equal ohms. Table 3 can be used for conversion. Even though the start current may be the same, the start torques may differ depending on the motor design. The PTCR has a fixed time built in. The start capacitor will stay in the circuit until a relay switches it out. The longer time provided by the capacitor and relay may be needed on applications where equalization is not present or adequate reset time is not available. Document Number: 23086 Revision 14-May-02 0.8 PTCR Switchout Xc = 1 2πfC Table 3 START CAPACITOR 50 microfarads 75 microfarads 100 microfarads 125 microfarads 200 microfarads 250 microfarads [email protected] PTCR VALUE 50 ohms 37.5 ohms 25 ohms 20 ohms 12.5 ohms 10 ohms www.vishay.com 5 305C Series Vishay Cera-Mite PTCR Motor Start Packages PTCR SELECTION • Choosing the best PTCR for an application is a simple matter. See Table 4 and Table 2. Vishay Cera-Mite PTCRs are available in three case sizes (A, B, and C). • Table 4 indicates the correct case size for the application. Table 2 shows how to choose the correct resistance value. • Using a device too small or resistance too high will give inadequate starting performance. An oversize device will not harm the motor, but may not be optimum with regards to acceleration dynamics, or power dissipation. • The PTCR is generally self protecting when applied within the voltage and current ratings. Table 4 PTCR MOTOR START SELECTION CHART VISHAY CERA-MITE PART CASE NUMBER STYLE 305C20* 305C21 305C22* 305C19* 305C12* 305C2 305C9* 305C11 305C1* C C C B B B A A A Note 1 RESISTANCE (OHMS) RDYN R0 ± 20% ± 30% 25 35 50 20 25 50 10 12.5 25 35 50 75 30 40 85 15 20 42.5 Note 2 SWITCH TIME (T) SECONDS @ 230V CURRENT RATING AMPERES MAX. VOLTAGE RATING VOLTS, RMS 0.25 0.35 0.50 0.50 0.60 1.00 0.50 0.60 1.00 10 8 6 18 15 12 36 30 24 410 410 410 500 500 500 500 500 500 Note 3 Note 4 Note 5 AVG. POWER DISSIPATION WATTS 3.5 3.5 3.5 7 7 7 9 9 9 Note 6 COMPRESSOR RANGE BTU (000) HP 10 - 28 8 - 18 5 - 12 20 - 50 18 - 42 10 - 25 28 - 68 28 - 62 14 - 36 0.75 - 2.0 0.5 - 1.5 0..25 - 1.0 1.5 - 4.0 1.5 - 3.5 1.0 - 2.5 3.0 - 7.0 3.0 - 6.0 1.5 - 3.5 Note 7 * Preferred Values Note 1 Part number is stamped on the device for UL recognition. The customer part number will also include 1 or 3 character alpha-numeric suffix to designate mounting bracket, customer marking, wire jumper, or other accessory furnished. The suffix is not marked on the part. Certified outline drawing and complete part number will be furnished on request for specific applications. (Example: 305C19K01.) Mounting brackets and other accessories are shipped in separate boxes to simplify installation in end use equipment. Note 2 RDYN is nominal resistance equal to E/I when 230 volts, 60 Hz is applied (See Fig T-7). This resistance determines current and starting torque at the moment of application of voltage to the motor and can be measured with an oscilloscope. For receiving inspection or routine trouble shooting, the D.C. resistance (Ro) as measured with an ohmmeter is approximately 50% greater. For example: 305C20 measured with an ohm meter would be 35 ohms ± 30% tolerance. www.vishay.com 6 Note 3 Resistance values are duplicated in several case sizes (ie: 305C20, C12, and C1) to provide longer switch time (t) and higher current ratings (See Fig T-7). Larger parts may be needed for more difficult starting conditions (voltage or temperature) or may be used for accelerating fans against back pressure. Note 4 Maximum current in the PTCR is determined by Max Line Voltage Min RDYN Motor auxiliary winding impedance is usually small compared to PTCR resistance, and does not materially affect PTCR current. Current in PTCR is a percentage of the full motor inrush (locked rotor) current; usually 30% to 50% (See Fig T-5). Note 5 In application, the maximum voltage is the voltage that appears across the [email protected] run capacitor at rated speed, high line, light load. This is not the applied line voltage (See Fig T-6). THESE DEVICES ARE INTENDED FOR APPLICATION ON 240 VOLT LINES OR SYSTEMS WITH MAXIMUM LINE VOLTAGE UP TO 264 VOLTS. The 305C20, 21 and 22 are also used on 120 volt systems where the motor is designed to use same run capacitor and PTCR as equivalent 230 volt compressor. Note 6 This is the power used to keep the PTCR switched off under full load running conditions at typical ambient temperature. Note 7 BTU and horsepower ranges are for reference only. PTCR may be applied outside those ranges as long as maximum voltage and maximum current are not exceeded. Scroll and rotary compressors may require less starting assistance allowing use of smaller devices. Document Number: 23086 Revision 14-May-02 305C Series PTCR Motor Start Packages Vishay Cera-Mite DIMENSIONS FOR PTCR MOTOR START DEVICES - IN INCHES • PACKAGED MOTOR START PTCRs ARE OFFERED IN THREE DIFFERENT CASE SIZES TO ACCOMMODATE THE RANGE OF PSC COMPRESSOR MOTORS SERVED. CASE STYLE C CASE C 305C20 — Black 305C21 — Black 305C22 — Black Case Style C is a 2-terminal single pellet device with current carrying capacity up to 10 amperes. It is furnished with a round mounting bracket. .920 .980 .609 .641 Fig T-8 1.780 max MOUNTING BRACKET 36-520M — Round .329 .358 .975 1.025 .135 DIA. .140 Weld Projection (2) Round Bracket — Spring Steel Phosphate & Oil Finish. Accepts #6 Sheet Metal Screw .298 .328 .050 HT. TYP. .175 WD. TYP. .200 max .810 .880 .579 .609 CASE STYLE B Case Style B is a 2-terminal single pellet unit with current carrying capacity up to 18 amperes. Depending upon the model, either a U-shaped or round bracket is furnished. CASE B MOUNTING BRACKET 7-36-5C — U-Shaped 36-520H — Round 305C2 — Black 305C12 — Black or Blue 305C19 — Blue Fig T-9 Weld Projection (3) .050 HT. TYP. .175 WD. TYP. .15 OD x .055 HT 4 places 2.37 max .213 .223 DIA. .650 max .25 max. 2 places .135 DIA. .140 .298 .328 1.490 1.510 1.05 1.430 1.530 .20 TYP. 1.344 1.406 .110 Nail Pierce .120 REF. .990 1.010 1.475 1.525 .550 .580 .579 .609 1.44 max 1.50 max U-Bracket — Spring Steel Zinc Dichromate Finish. Accepts #8 Sheet Metal Screw Round Bracket — Spring Steel Phosphate & Oil Finish. Accepts #6 Sheet Metal Screw CASE STYLE A Case Style A is a 3-terminal device that incorporates two pellets in parallel, resulting in lower resistance values and current carrying capacity up to 36 amperes. A jumper wire to complete the parallel connection with the two internal pellets is required. CASE A 305C1 — Blue 305C9 — Tan 305C11 — Tan Fig T-10 .185 .190 DIA. 5.25 max 2.75 max (To End of Q.C.) .990 1.010 .15 OD X .055 HT 4 Places .20 TYP. MOUNTING BRACKET WIRE JUMPER 7-36-4C — U-Shaped 50-1278 — 9.75” Long 105°C Wire 36-520H — Round .110 Nail Pierce .120 REF. Weld Projection (2) .050 HT. TYP. .175 WD. TYP. .298 .328 1.05 1.590 1.690 1.716 1.781 .135 DIA. .140 1.490 1.510 1.44 max .650 max .25 max 3 Places 1.475 1.525 .550 .580 .579 .609 U-Bracket — Spring Steel Zinc Dichromate Finish. Accepts #8 Sheet Metal Screw 1.50 max Round Bracket — Spring Steel Phosphate & Oil Finish. Accepts #6 Sheet Metal Screw OPERATING TEMPERATURE CONNECTION DIAGRAMS Under normal operation, the ceramic pellet inside the case reaches a temperature of 150°C. The plastic case material has been recognized by UL for operation up to this temperature. The actual temperature on the outside of the case will be approximately 100°C while the motor is running. An appropriate mounting location and 105°C, 600 volt wiring are recommended. PTCR Motor Start units are connected directly across the PSC motor’s “run” capacitor. Case style A is a 3-terminal device and uses an external jumper wire to connect the two internal pellets in parallel. A special “piggyback” terminal on the jumper wire provides for two connections on one side of the A-style case. Document Number: 23086 Revision 14-May-02 Fig T-11 Fig T-12 Motor Run Cap Motor Run Cap A Style 3-Terminal Case [email protected] B & C Style 2-Terminal Case www.vishay.com 7 305C Series Vishay Cera-Mite PTCR Motor Start Packages VISHAY CERA-MITE MOTOR START FEATURES ADVANCED CERAMIC ENGINEERING FOR HVAC Vishay Cera-Mite’s capability in large diameter ceramic pellets, unique formulations tailored to motor starting, and heavy duty electrode systems, have been developed and proven with the cooperation of HVAC industry experts over a period of 20 years. INHERENT PERFORMANCE Large diameter pellets make possible low resistance start devices needed to match torque requirements of high efficiency compressor motors. Various package sizes offer selection of timing intervals, providing optimum switching time without dependence on sensing speed, counter EMF, or current. RUGGED MECHANICAL CONSTRUCTION Vishay Cera-Mite PTCR cases are molded from a UL94V0 high temperature, engineered plastic/glass composite. Heavy duty aluminum contact plates and stainless steel force springs are scaled to the pellet sizes and current ratings to insure no internal arcing and to enhance quick reset time. Unbreakable metal mounting brackets attach securely with a single screw. The NEW “U” - brackets developed by Vishay Cera-Mite feature lower power consumption and greater reliability by maximizing case to ground thermal impedance. SIMPLE AND ECONOMICAL A solid state device requiring only 2 quick connect wires and one bracket screw to install. Compared to the alternative start capacitor and relay, PTCR start devices save several wires, occupy less panel space, mount more easily, and cost less. OUTSTANDING RELIABILITY Over a fifteen year period, with an installed base of millions of Vishay Cera-Mite PTCR start devices, experience has demonstrated reliability at 1.0 FITS or less. Users have benefited from very low warranty expense. RESTART CONSIDERATIONS Fig T-13 A properly sized PTCR will provide adequate starting current and starting time with a cool down time of 3 to 5 minutes, coordinating perfectly with standard “off delay” equalization timers Restart characteristics of the three case sizes are shown. 100 Fig T-15 CASE STYLE B CASE STYLE C 100 CASE STYLE A 100 Cold Start Cold Start Cold Start 75 75 75 % Initial 50 Current 50 50 5 Min. Cooling 25 0 www.vishay.com 8 Fig T-14 3 Min. Cooling 0 3 Min. Cooling 5 Min. Cooling 25 .2 .4 .6 Time In Seconds .8 0 0 3 Min. Cooling 5 Min. Cooling 25 .2 .4 .6 .8 Time In Seconds [email protected] 1.0 0 0 .2 .4 .6 .8 Time In Seconds 1.0 1.2 Document Number: 23086 Revision 14-May-02