AIM Manual

Motor Maintenance » Single-Phase Motors and Controls (Page 49)

Ohmmeter Tests

QD, Solid State Control Box (Power Off)

  • A. START CAPACITOR AND RUN CAPACITOR IF APPLICABLE (CRC)
  • 1. Meter Setting: R x 1,000.
  • 2. Connections: Capacitor terminals.
  • 3. Correct meter reading: Pointer should swing toward zero, then back to infinity.
  • B. Q.D. (BLUE) RELAY
  • Step 1. Triac Test
  • 1. Meter setting: R x 1,000.
  • 2. Connections: Cap and B terminal.
  • 3. Correct meter reading: Infinity for all models.
  • Step 2. Coil Test
  • 1. Meter Setting: R x 1.
  • 2. Connections: L1 and B.
  • 3. Correct meter reading: Zero ohms for all models.
  • C. POTENTIAL (VOLTAGE) RELAY
  • Step 1. Coil Test
  • 1. Meter setting: R x 1,000.
  • 2. Connections: #2 & #5.
  • 3. Correct meter readings:
  • For 115 Volt Boxes: 0.7-1.8 (700 to 1,800 ohms).
  • For 230 Volt Boxes: 4.5-7.0 (4,500 to 7,000 ohms).
  • Step 2. Contact Test
  • 1. Meter setting: R x 1.
  • 2. Connections: #1 & #2.
  • 3. Correct meter reading: Zero for all models.

Ohmmeter Tests

Integral Horsepower Control Box (Power Off)

  • A. OVERLOADS (Push Reset Buttons to make sure contacts are closed.)
  • 1. Meter Setting: R x 1.
  • 2. Connections: Overload terminals.
  • 3. Correct meter reading: Less than 0.5 ohms.
  • B. CAPACITOR (Disconnect leads from one side of each capacitor before checking.)
  • 1. Meter Setting: R x 1,000.
  • 2. Connections: Capacitor terminals.
  • 3. Correct meter reading: Pointer should swing toward zero, then drift back to infinity, except for capacitors with resistors which will drift back to 15,000 ohms.
  • C. POTENTIAL (VOLTAGE) RELAY
  • Step 1. Coil Test
  • 1. Meter setting: R x 1,000.
  • 2. Connections: #2 & #5.
  • 3. Correct meter readings: 4.5-7.0 (4,500 to 7,000 ohms) for all models.
  • Step 2. Contact Test
  • 1. Meter Setting: R x 1.
  • 2. Connections: #1 & #2.
  • 3. Correct meter reading: Zero ohms for all models.
  • D. CONTACTOR
  • Step 1. Coil
  • 1. Meter setting: R x 100
  • 2. Connections: Coil terminals
  • 3. Correct meter reading: 1.8-14.0 (180 to 1,400 ohms)
  • Step 2. Contacts
  • 1. Meter Setting: R X 1
  • 2. Connections: L1 & T1 or L2 & T2
  • 3. Manually close contacts
  • 4. Correct meter reading: Zero ohms

Caution: The tests in this manual for components such as capacitors, relays, and QD switches should be regarded as indicative and not as conclusive. For example, a capacitor may test good (not open, not shorted) but may have lost some of its capacitance and may no longer be able to perform its function.