PTC Thermistors Motor Start Packages - Vishay

1 PTC305C Series Vishay Cera-Mite PTC Thermistors Motor Start Packages FEATURES. Large diameter ceramic pellets for high starting current Various package sizes for optimum inrush current and switching time Rugged mechanical construction for reliable long life operation UL approved Packages Plastic case mold UL 94 V-0 approved Adapted accessories for easy mounting Material categorization: for definitions of compliance please see QUICK REFERENCE DATA. PARAMETER VALUE UNIT. Resistance value at 25 C 15 to 75 APPLICATIONS. Tolerance on resistance value 30 % Single phase Motor Start assist in Maximum current ratings 6 to 36 ARMS - Refrigerator systems Switching temperature 110 to 120 C - Air-conditioning systems Switching times (typical) to s - Heat-pumps Maximum voltage rating 410, 500 VRMS - Small compressors Operating temperature range -10 to +80 C. Storage temperature range -25 to +105 C. PTC Motor Start SELECTION CHART. MAX. SWITCH CURRENT COMPRESSOR COMPRESSOR.

2 Vishay CERA-MITE CASE RDYN ( ) R25 ( ) VOLTAGE. TIME RATING RANGE RANGE. PART NUMBER STYLE 20 % 30 % RATING. t (s) at 230 V (ARMS) (BTU 000) (HP). (VRMS). PTC305C20 C 25 35 10 410 10 to 28 to PTC305C21 C 35 50 8 410 8 to 18 to PTC305C22 C 50 75 6 410 5 to 12 to PTC305C19 B 20 30 18 500 20 to 50 to PTC305C12 B 25 40 15 500 18 to 42 to PTC305C2 B 50 85 12 500 10 to 25 to PTC305C9 A 10 15 36 500 28 to 68 to PTC305C11 A 20 30 500 28 to 62 to PTC305C1 A 25 24 500 14 to 36 to PTC Motor Start ACCESSORY SELECTION CHART. ACCESSORY . DESCRIPTION. PART NUMBER. PTCAUX36-520M Round mounting bracket for case style C. PTCAUX36-520H Round mounting bracket for case style A and B. PTCAUX7-36-5C U-shaped mounting bracket for case style B. PTCAUX7-36-4C U-shaped mounting bracket for case style A. PTCAUX50-1278 Jumper wire for case style A. Revision: 11-Sep-15 1 Document Number: 23086. For technical questions, contact: THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE.

3 THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT. ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT PTC305C Series Vishay Cera-Mite ECONOMICAL SOLID STATE TORQUE ASSIST FOR HEAT PUMPS, ROOM AIR, COMMERCIAL AND. RESIDENTIAL AIR CONDITIONING AND REFRIGERATION SYSTEMS. Positive Temperature Coefficient Themistors (PTC) have Safety Agency Recognition been used for many years in millions of HVAC applications Vishay Cera-Mite Motor Start PTC Thermistors are to provide starting torque assistance to Permanent Split recognized by Underwriter Laboratories file E97640 in Capacitor (PSC) single phase compressor motors. accordance with standard for controllers and refrigeration Sizes are available to cover the full range of 120 V/240 V components UL 873 or UL 60730; and Canadian Standard PSC compressor motors. No. 24. All Packages and accessories are RoHS-compliant. RELATIVE COMPARISON OF VARIOUS Motor STARTING METHODS. Three methods have historically been employed to generate The importance of each category is dependent upon the starting torque for PSC motors.

4 All are well-proven Motor application and industry sector. technologies and may be compared relative to one another In general, if the PTC starter produces sufficient starting based upon categories shown below. torque, it is considered the simplest and most economical choice. Table 1. MECHANICAL ELECTRICAL FINANCIAL. STARTING EASE SENSITIVE. PANEL ACCELERATION ACCELERATION RESET INVENTORY. METHOD TO EMI/RFI PURCHASED. OF SPACE TORQUE (SWITCH) TIME TECHNOLOGY MIX RELIABILITY. MOUNTING GENERATED COST. WIRING REQUIRED PRODUCED TIME REQUIRED REQUIRED. DIRECTION. Simple 3 min to PTC starter Lowest No Lowest Fixed No Solid State Lowest Highest Lowest 2 wire 5 min Start cap Moderate with PTC 2 min to 2 wire or Medium Yes Medium Fixed No Solid State Medium Medium Medium acting as a 5 min 3 wire current relay Start cap Difficult Variable used with Electro 4 wire or Highest Yes Highest based on None Yes Highest Lowest Highest potential or Mechanical 5 wire Motor speed current relay SIMPLIFIED PTC STARTING DIAGRAM.

5 Start Sequence Restart When starting the compressor, contactor (M) closes; the It is important to provide time between Motor starts to allow PTC, which is at low resistance, provides starting current to the PTC to cool to near its initial temperature. This time is the Motor 's auxiliary winding. After time delay (t), the current usually 3 min to 5 min and is determined by the thermostat passing through the PTC causes it to heat and switch to a (THERM) or separate time-delay relay (TR). Attempts to very high resistance. At this point the Motor is up to speed restart in less time may be successful depending on and the run capacitor (CR) determines the current in the compressor equalization, line voltage, temperature, and auxiliary winding. The PTC remains hot and at high other conditions. If the Motor were to stall in a locked-rotor resistance as long as voltage remains on the circuit. When state, overload device (PD or TS) would open the line and a contactor (M) opens, shutting off voltage to the compressor, further time delay would occur until the Motor overload is the PTC cools to its initial low resistance and is again ready reset.

6 Motor Start PTCs are applied to compressors having to provide torque assist on the next startup. means to equalize pressure during shutdown. Fig T-2 TYPICAL PTC CHARACTERISTICS . L1 PD AS A Motor Start DEVICE. M Protective PSC Fig T-3. THERM TS Motor . Device CURRENT. Internal 10 000 Motor MAIN. TR. PTC Resistance ( ). PTC Current (ARMS). M Winding Overtemp AC Line Switch 1000 120 or 240 Optional OFF. VOLTS AC Time Delay TR CR AUX. Relay M. 100 Switch Time (t) Protective Device M PTC RESISTANCE. L2. Low Voltage Control Transformers Not Shown 10 50 100 150. PTC Temperature C. Revision: 11-Sep-15 2 Document Number: 23086. For technical questions, contact: THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT. ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT PTC305C Series Vishay Cera-Mite Start AND ACCELERATION TORQUES SINGLE PHASE PSC HIGH EFFICIENCY COMPRESSORS. The use of a PTC Start assist insures sufficient acceleration torque to overcome not only breakaway friction, but also parasitic asynchronous torques associated with the 5th and 100.

7 7th Motor harmonics or lamination slot harmonics. A1 Full Load max. A2 Operating Point Torque Acceleration Time Considerations Percent Rated Speed 75. The time to accelerate a rotating machine is: 2 2. RPM x WK lb ft . accelerating time (s) = ---------------------------------------- ---------------------------------- 50. average torque lb ft x 308 B1 B2. average torque = curve B - curve A . 25. 1. If (curve B - curve A) is zero or less, the Motor may stall. 5th Possible Region of 2. In calculating torque available from curve B, allowance 7th Harmonic Torques should be made for cusps in the torque curve due to 0 Slot 100 200. harmonics. The time needed to accelerate from rest to Cold Breakaway Torque Percent Rated Torque 1/2 speed is critical, as the average torque available in this region is limited. Select a PTC with sufficient CURVE A1 CURVE A2 CURVE B1 CURVE B2. Torque req'd Torque req'd Motor speed Motor speed switching time (t) to accelerate the compressor.

8 To accelerate to accelerate versus torque versus torque unloaded compressor at with run cap with run cap 3. Scroll and rotary compressors may have less breakaway compressor partial differential only and PTCR. torque than shown. pressure 4. A compressor with no equalization may require over 100 % starting torque and time as long as several seconds. PTC starters not recommended. CONSIDERATIONS FOR CURRENT IN PTC APPROXIMATE EQUIVALENT CIRCUIT PSC Motor . AT ZERO SPEED. HP x 746. I L run = ---------------------------------- x I L Start I L run Fig. T-5. V M x pf x eff Line Voltage V M. For running conditions: L1 L2. IL. If V aux = V M then I M and I aux = ------- 2 IL IM RM (1) XM (1). IL VM VM I aux If V aux V M then I aux = ------- x ------------ and Z aux = ---------- Ic 2 V aux I aux C. For the greatest starting torque, PTC should be chosen Raux Xaux PTC. to make: V M x I M = V aux x I aux . In many cases the auxiliary Vaux IR. Volt-Amperes are limited to about 50 % of the main winding Volt-Amperes to get 50 % to 70 % rated torque.

9 * R and X are total of stator and rotor Then at Start , with PTC in series: Fig T-6. Z' aux = R +Z . PTC aux Simplified voltage diagram of the PSC Motor at operating VM speed. I Rstart through PTC = ------------ . Z aux Note VM 1 (1) I (auxiliary current) leads I (main current) by 80 to 90 when C. A M. I Cstart through Run Cap = -------; X C = ------------- (run capacitor) is chosen for balanced operation at 3/4 to full XC 2 fC. load. Line Power Factor = sine 2 . I aux Start = I +I VM. R Start C Start If Zaux is low impedance, less than 10 % of RPTC Applied Voltage VM (1). then it can be ignored and IPTC at Start = ---------------- xC. R PTCR = IA. =V. C IM. C. This closely approximates the condition for motors over 1/2 V PT IA (1). VA. HP. Revision: 11-Sep-15 3 Document Number: 23086. For technical questions, contact: THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT. ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT PTC305C Series Vishay Cera-Mite EFFECT OF PTC RESISTANCE ON STARTING TORQUE OF PSC MOTORS.

10 Table 2. Motor HP LOCKED ROTOR TORQUE WITH STARTING TORQUE WITH RUN CAP AND PTC (% RATED TORQUE) (SEE B). (TABLE 4) RUN CAP ONLY % RATED TORQUE RESISTANCE (RDYN). (NOTE 7) (SEE A) 50 25 20 10 . 25 % to 35 % 70 % to 100 % 80 % to 100 % NA NA NA. 1 25 % to 35 % 50 % to 70 % 70 % to 100 % NA NA NA. 2 20 % to 30 % 40 % to 60 % 60 % to 90 % 70 % to 100 % 70 % to 100 % 80 % to 100 %. 20 % to 30 % NA 40 % to 60 % 50 % to 85 % 60 % to 90 % 70 % to 100 %. 5 15 % to 25 % NA NA 40 % to 60 % 50 % to 75 % 60 % to 90 %. 15 % to 25 % NA NA NA 40 % to 70 % 50 % to 80 %. A. Rated torque is the torque at full speed rated load. B. Figure T-4 shows effect of using PTC to increase starting It is calculated as: torque. For reciprocating compressors, it is advised to HP x 5250. Torque lb - ft = ---------------------------- choose a resistance value that gives at least 50 % rated RPM torque at locked rotor. Scroll and rotary compressors The range shown includes both normal slip and high may require less torque.