Rob Will
07-22-2007, 1:40 AM
Today, we ran low voltage wire about the shop for DC control stations. The magnetic starter for the 7.5 hp 3 ph blower motor is equipped with a 24V AC coil.
I bought a small 24V transformer at the electric supply house. Unfortunately, when we try to energize the starter's coil, the contactor just hums and fails to close. At first we suspected voltage drop in our control station wiring..... but the coil fails to close even if we bypass all that and hook it up direct. In a no load situation, the transformer shows the correct 24V. When exposed to the load of the starter coil, the transformer will only hold 14V. If we manually engage the contactor, the transformer apparently has enough voltage to "run hold", it just does not have enough "umphhh" to close the contacts on its own.
The starter is a Cutler Hammer in a NEMA size 1. We checked the coil and it is correct (24V AC). Anybody had experience with a transformer that could not carry a motor starter? I can get a better transformer Monday at the motor shop but any other opinions are welcome.
Rob
I bought a small 24V transformer at the electric supply house. Unfortunately, when we try to energize the starter's coil, the contactor just hums and fails to close. At first we suspected voltage drop in our control station wiring..... but the coil fails to close even if we bypass all that and hook it up direct. In a no load situation, the transformer shows the correct 24V. When exposed to the load of the starter coil, the transformer will only hold 14V. If we manually engage the contactor, the transformer apparently has enough voltage to "run hold", it just does not have enough "umphhh" to close the contacts on its own.
The starter is a Cutler Hammer in a NEMA size 1. We checked the coil and it is correct (24V AC). Anybody had experience with a transformer that could not carry a motor starter? I can get a better transformer Monday at the motor shop but any other opinions are welcome.
Rob